Which statement is true of the equation shown below? H₂O ⇌ H+ + OH−
  • Polar Groups attract one anotherPolar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • They consist of weak acids and weak basesBy using weak acids and bases, the buffer can absorb or give off H+, stabilizing the pH
  • It results from hydrogen bondingIt helps pull water through plantsIt involves both cohesion and adhesionBecause of hydrogen bonding, water coheres to itself and adheres to cell walls. That makes it possible to pull water through plants without breaking the water column.
  • It omits an important water molecule and it is a standard shorthand for water dissociationChemists use this shorthand equation for simplicity and to emphasize H+, but in reality an H+ jumps from one water molecule to another, making hydronium and OH-.
Which is true of water's tensile strength?
  • Oxygen has four valence orbitalsOxygen is much more electronegative than hydrogenThe electronegativity difference creates charges that make hydrogen bonds possible, and the four outer orbitals permit water to make four hydrogen bonds. The result is a three-dimensional network of bonds between water molecules.
  • It results from hydrogen bondingIt helps pull water through plantsIt involves both cohesion and adhesionBecause of hydrogen bonding, water coheres to itself and adheres to cell walls. That makes it possible to pull water through plants without breaking the water column.
  • Hydrogen bonds between surface water molecules resist being stretched.The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.
  • It omits an important water molecule and it is a standard shorthand for water dissociationChemists use this shorthand equation for simplicity and to emphasize H+, but in reality an H+ jumps from one water molecule to another, making hydronium and OH-.
Water's surface tension and heat storage capacity are accounted for by its _____.
  • Hydrogen bonds between surface water molecules resist being stretched.The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.
  • Nitrogen, Carbon, Hydrogen, & Oxygen
  • Hydrogen bonds
  • HydrogenOxygenMany reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.
Water is a versatile ________ .
  • Donates H+ to waterAcids are defined by the ability to donate H+ to water.
  • Solvent
  • Hydrogen bonds
  • A water molecule can make 4 hydrogen bonds.When you heat water, much of the heat is used to break hydrogen bonds. Only the remaining heat can increase molecular motion, raising the temperature.
Hydrogen is the source of ____ and ____ for chemical reactions in the cells
  • Hydrogen bonds between surface water molecules resist being stretched.The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.
  • HydrogenOxygenMany reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.
  • HydrogenA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
  • Rotation can occur around single bondsRotation allows groups of atoms to change position while preserving the usual bond angles around each atom.
Basic pH has higher or lower [H+]?
  • Absorption by the oceans of carbon dioxide generated by burning fossil fuels
  • A water molecule has four orbitals
  • Donates H+ to waterAcids are defined by the ability to donate H+ to water.
  • LowerLow pH has more [H+] (more basic)
Factory smoke has led to acid rain that lowered the pH of a lake to 5.What is the H+ concentration in the lake?
  • 10⁻⁵ MThe pH is the negative exponent of the H+ concentration.
  • Wrong! Two hydrogen bonds are not in the plane of the atoms.The array of hydrogen bonds is three-dimensional.
  • 4, 1, 2, 3 H: 1O: 2N: 3C: 4
  • Can form between H & NDo not occur in water moleculesDo not share electrons between two bonded atomsAre not covalent bondsThey can also form between H and other highly electronegative atoms, such as O, if the atoms have strong partial charges.
A(n) ________ refers to two or more atoms held together by covalent bonds.
  • FourThere are four electrons in the outermost electron shell
  • Glycerol is the solventIn any solution, the most abundant substance is the solvent.
  • MoleculeA molecule is defined as two or more atoms held together by covalent bonds.
  • IsotopeAtomic forms of an element with the same number of protons but different numbers of neutrons are isotopes.
How much carbon dioxide from the atmosphere is absorbed by the oceans on a daily basis?
  • All the atoms lie in a plane
  • 20 million metric tons
  • 6 electrons
  • Compound
Blood and other biological fluids are aqueous solutions with a diversity of dissolved ________ .
  • Solutes
  • Polarity
  • True
  • Shellfish
Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?
  • Polar Groups attract one anotherPolar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • The valence shell needs 8 electronsWithout help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
  • These atoms are isotopes.Atoms with the same atomic number and different atomic masses are referred to as isotopes.
  • Fill shells without giving atoms much chargeBring electrons closer to protonsElectron-sharing brings electrons closer to nuclei and it fills shells without giving the atoms much charge. Both factors stabilize the bond.
Dr. Haxton told his class that a water molecule can make 4 hydrogen bonds, all of them in the same plane as the three atoms. What would a good student reply?
  • 4, 1, 2, 3 H: 1O: 2N: 3C: 4
  • O, N, C, HRemember this, and you'll be able to predict polarity when molecules have O or N linked to C or H.
  • Wrong! Two hydrogen bonds are not in the plane of the atoms.The array of hydrogen bonds is three-dimensional.
  • 5O and N can make hydrogen bonds, as can each H attached to O or N.
Hydrogen Bonds are weaker than covalent bonds because they do not involve sharing of electrons, and they are weaker than ionic bonds because they involve the attraction of partial (not full) opposite charges.
  • Ionic BondsSalt
  • Which bond weaker? Hydrogen or Covalent?
  • Raise it to 100 times its present value.
  • 42 e- in first shell8 e- in second shell
Acidic pH has higher or lower [H+]?
  • ElementThis is the definition of an element
  • An attraction between ions of opposite charge.This is the definition of an ionic bond
  • Donates H+ to waterAcids are defined by the ability to donate H+ to water.
  • HigherHigh pH has less [H+] (more acidic)
Buffers work best when
  • The number of electrons in the outermost electron shell.An atom is least likely to participate in a reaction when its outermost shell is stable.
  • About half of the buffer molecules are dissociatedThat arrangement gives the least change in pH when either acid or base is added
  • Polar CovalentWhile oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.
  • Corals and coral reefs are not able to form their hard skeletonsClams, mussels, lobsters, and shrimp are not able to form strong enough shells
The number of protons in an uncharged atom _____.
  • CovalentA covalent bond is one in which electron pairs are shared.
  • Equals the total number of electrons in the orbital shellsThe atom has an equal number of protons and electrons, which gives it a neutral charge overall.
  • Structural FormulaThis kind of model is designed to show which atoms are bound to one another, but it doesn't accurately picture the sizes of atoms.
  • The valence shell needs 8 electronsWithout help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
Each water molecule is joined to _____ other water molecules by ____ bonds.
  • Heat
  • FourHydrogen
  • Electronegative
  • Two polar covalent bonds
Fluorine's atomic number is 9 and its atomic mass isHow many neutrons does fluorine have?
  • Carbon dioxide reacts with seawater, forming carbonic acid
  • Hydrogen ions is equal to the concentration of hydroxide ionsThis is the definition of a neutral solution
  • Atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).
  • Electrons in two orbitalsA double bond involves two orbitals, each with a shared pair of electrons.
Without making or breaking bonds, a molecule can change its shape because ...
  • Corals and coral reefs are not able to form their hard skeletonsClams, mussels, lobsters, and shrimp are not able to form strong enough shells
  • Rotation can occur around single bondsRotation allows groups of atoms to change position while preserving the usual bond angles around each atom.
  • Absorption by the oceans of carbon dioxide generated by burning fossil fuels
  • It takes energy to break hydrogen bondsAt boiling, all the added heat is used to break hydrogen bonds. Free of the water mass, the departing steam carries away all the added energy, with none left over to raise the temperature.
The body uses atoms in different ways to accomplish different tasks. For example, one portion of the body's calcium supply strengthens bones, whereas another portion combines with proteins to stimulate blood clotting after tissue injury. Which of the following statements provides the most logical chemical explanation of calcium's ability to perform such different functions?
  • The bone contains calcium salts, which are less reactive than the calcium ions found in blood
  • It's the same reaction running backward or forwardThe buffer accepts H+ in one case; it gives off H+ in the other case
  • The concentrations of hydronium and hydroxide ions are equal.In a neutral solution the concentrations of hydroxide and hydronium ions must be equal.
  • Hydrogen ions is equal to the concentration of hydroxide ionsThis is the definition of a neutral solution
What factors are important in making it possible to cool yourself by sweating?
  • ElectronsElectrons are negatively charged particles. In a neutral atom, the number of electrons is equal to the number of protons. When an atom loses or gains electrons, its charge becomes positive or negative, respectively.
  • Polar Groups attract one anotherPolar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • PolarThe electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
  • Molecules collide with varied angels and degreesHydrogen bonds are relatively weakRandom collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
An element has 8 protons, 9 neutrons, and 8 electrons. Its atomic number and its mass number, respectively, are _____.
  • The solution on the right is basic relative to the solution on the leftThe solution on the right has a lower concentration of hydrogen ions relative to hydroxide ions than does the solution on the left.
  • The number of electrons in the outermost electron shell.An atom is least likely to participate in a reaction when its outermost shell is stable.
  • 8 & 17The number of protons, 8, gives the atomic number. The mass number is the sum of the number of protons and neutrons, or 8 plus 9, which equals 17.
  • PolarThe electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
The innermost electron shell of an atom can hold up to ________ electrons.
  • Structural FormulaThis kind of model is designed to show which atoms are bound to one another, but it doesn't accurately picture the sizes of atoms.
  • Electronegativity
  • The H atoms in water have partial positive charges.
  • 2 electrons is the maximum count for the ________ This is the maximum number of electrons that can occupy the ________
The ammonia molecule in the diagram has the observed bond orientation because ..
  • Can form between H & NDo not occur in water moleculesDo not share electrons between two bonded atomsAre not covalent bondsThey can also form between H and other highly electronegative atoms, such as O, if the atoms have strong partial charges.
  • N has four pairs of electrons in the valence shellElectrons repel one anotherN has 7 protons in its nucleusSince N has 7 protons, it must fill the second shell, giving it 4 pairs of electrons. The electrons form 3 bonds and 1 lone pair of electrons. Each pair of electrons repels the other pairs, so they are equally far apart.
  • PolarThe electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
  • Molecules collide with varied angels and degreesHydrogen bonds are relatively weakRandom collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
he water molecule has a bent shape because ...
  • Oxygen has four valence orbitalsOxygen is much more electronegative than hydrogenThe electronegativity difference creates charges that make hydrogen bonds possible, and the four outer orbitals permit water to make four hydrogen bonds. The result is a three-dimensional network of bonds between water molecules.
  • Hydrogen bonds break and re-form rapidlyThere are always enough hydrogen bonds to hold the water together, but the bonds break and re-form rapidly, allowing molecules to move relative to one another.
  • 10⁻⁵ MThe pH is the negative exponent of the H+ concentration.
  • Oxygen has two unbonded pairs of valence electronsRepulsion between electrons governs the angles between bonds. The two pairs of unbonded electrons repel the two pairs of bonding electrons, creating the bend in the molecule.
Why is ice less dense than liquid water?
  • Have a weak acid or a weak base half ionized in waterWhen half of the molecules are ionized, there are plenty of molecules that can either absorb H+ or give off H+ when the pH is disturbed from outside.
  • Polar Covalent BondsThe hydrogen and oxygen atoms do not equally share their electrons, which results in the formation of electronegative oxygen atoms and electropositive hydrogen atoms. These are then able to interact with other water molecules to form hydrogen bonds.
  • Water molecules make hydrogen bonds at definite anglesCold molecules move less than warm moleculesThe ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.
  • Molecules collide with varied angels and degreesHydrogen bonds are relatively weakRandom collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
When water warms or cools, ________ either break or form.
  • Down (basic)
  • Hydrogen Bonds
  • Hydrogen bonds between surface water molecules resist being stretched.The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.
  • Electron-sharing
Which statement is true of pH buffers?
  • Rely much less on electron-sharingCovalent bonds are entirely based on sharing electrons, whereas ionic bonds are attractions between ions that keep their electrons.
  • Electrons in two orbitalsA double bond involves two orbitals, each with a shared pair of electrons.
  • The valence shell needs 8 electronsWithout help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
  • They consist of weak acids and weak basesBy using weak acids and bases, the buffer can absorb or give off H+, stabilizing the pH
Because ________ is less dense than liquid water, it floats and protects lakes and oceans from freezing solid.
  • Ice
  • Basic
  • Shellfish
  • Polarity
In a washing machine, the detergent raised the pH to 9.The concentration of OH- in the solution is ...
  • IsotopeAtomic forms of an element with the same number of protons but different numbers of neutrons are isotopes.
  • 10⁻⁵ M If you divide 10⁻¹⁴ by 10⁻⁹ M (the H+ concentration at pH 9), you get 10⁻⁵ M, the OH- concentration.
  • Look for undissociated molecules of baseStrong bases dissociate completely in solution; weak bases don't.
  • Hydrogen BondA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
Which answer helps to explain why all living cells need pH buffers?
  • Amino acid side chains have many carboxyl and amino groupsWhen these side chains ionize, they exert forces that affect the protein's folding. Thus, if pH isn't stabilized, the proteins will change their folding and may not function properly.
  • The valence shell needs 8 electronsWithout help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
  • Molecules collide with varied angels and degreesHydrogen bonds are relatively weakRandom collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
  • It results from hydrogen bondingIt helps pull water through plantsIt involves both cohesion and adhesionBecause of hydrogen bonding, water coheres to itself and adheres to cell walls. That makes it possible to pull water through plants without breaking the water column.
The higher the pH number, the higher the concentration of __ in a solution
  • Acid
  • True
  • OH+
  • H+
An atom with four electrons in the valence shell can form up to ________ single covalent bonds
  • IonWhen the proton number and electron number are unequal, the atom or molecule has a net positive or negative charge.
  • FourThere are four electrons in the outermost electron shell
  • Glycerol is the solventIn any solution, the most abundant substance is the solvent.
  • IonicSodium and chlorine ions are attracted to each other.
Partial charges occur when ...
  • One mole of solute per liter of solutionTo make the solution, you dissolve the solute in some solvent and then add more solvent to bring the volume up to a liter.
  • Polar CovalentWhile oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.
  • Atoms share electrons unequallyCovalent bond links atoms of two kindsEach kind of atom has a different attraction for electrons. Thus, atoms of different kinds share electrons unequally. That gives one atom a partial negative charge; the other atom a partial positive charge.
  • Has a very low pH valueHas a high hydronium ion concentrationVery acidic solutions have high hydronium concentrations, and as a result, have low pH values.
Which of the following can be considered strong bases?
  • H+O-H & O bonded by Polar Covalent BondWater molecules bonded by Hydrogen Bonds
  • CovalentA covalent bond is one in which electron pairs are shared.
  • NaOHThis is the only base that dissociates completely in water.
  • These atoms are isotopes.Atoms with the same atomic number and different atomic masses are referred to as isotopes.
Hydrogen Bonds
  • Can form between H & NDo not occur in water moleculesDo not share electrons between two bonded atomsAre not covalent bondsThey can also form between H and other highly electronegative atoms, such as O, if the atoms have strong partial charges.
  • Atoms share electrons unequallyCovalent bond links atoms of two kindsEach kind of atom has a different attraction for electrons. Thus, atoms of different kinds share electrons unequally. That gives one atom a partial negative charge; the other atom a partial positive charge.
  • Hydrogen bonds break and re-form rapidlyThere are always enough hydrogen bonds to hold the water together, but the bonds break and re-form rapidly, allowing molecules to move relative to one another.
  • Rely much less on electron-sharingCovalent bonds are entirely based on sharing electrons, whereas ionic bonds are attractions between ions that keep their electrons.
The open spaces in water's crystal structure make it possible for ...
  • Aquatic life to exist at the North PoleThe openings in the lattice make ice less dense than liquid water, so it floats. That causes water to freeze from the top down, so there's always liquid in which organisms can live.
  • O, N, C, HRemember this, and you'll be able to predict polarity when molecules have O or N linked to C or H.
  • N has four pairs of electrons in the valence shellElectrons repel one anotherN has 7 protons in its nucleusSince N has 7 protons, it must fill the second shell, giving it 4 pairs of electrons. The electrons form 3 bonds and 1 lone pair of electrons. Each pair of electrons repels the other pairs, so they are equally far apart.
  • Wrong! Two hydrogen bonds are not in the plane of the atoms.The array of hydrogen bonds is three-dimensional.
Oxygen is more ________ than hydrogen.
  • Solvent
  • They consist of weak acids and weak basesBy using weak acids and bases, the buffer can absorb or give off H+, stabilizing the pH
  • Electronegative
  • 2 electrons is the maximum count for the ________ This is the maximum number of electrons that can occupy the ________
Water Molecule partial charges and types of bonds
  • Oyster larvae cannot grow shells in acidified ocean waters
  • Corals and coral reefs are not able to form their hard skeletonsClams, mussels, lobsters, and shrimp are not able to form strong enough shells
  • Absorption by the oceans of carbon dioxide generated by burning fossil fuels
  • H+O-H & O bonded by Polar Covalent BondWater molecules bonded by Hydrogen Bonds
When full, the innermost electron shell of argon contains ________ electrons, and the outermost shell contains ________ electrons.
  • 2 & 8
  • The number of electrons in its outer shellOnly electrons are directly involved in the interactions between atoms, and the number of electrons in the outer shell determines the chemical behavior of the atom.
  • Basic
  • Solutes
A buffer consists of undissociated acid (HA) and the ion made by dissociating the acid (A-). How does this system buffer a solution against decreases in pH?
  • 1A knowledge of bonding capacities makes it easier to understand the structure of molecules.
  • It's the same reaction running backward or forwardThe buffer accepts H+ in one case; it gives off H+ in the other case
  • A- reacts with H+ to become HAA- binds most of the added H+, so not much H+ is left to lower the pH
  • 8 & 17The number of protons, 8, gives the atomic number. The mass number is the sum of the number of protons and neutrons, or 8 plus 9, which equals 17.
A positive ion with two units of charge has 10 neutrons and 8 protons. The ion also has ________.
  • Cohesion
  • Electronegativity
  • FourHydrogen
  • 6 electrons
Compounds that release OH- are bases because ...
  • OH- combines with H+ and removes it from solutionThis behavior of OH- earns the title of "base" for compounds that release OH-.
  • Hydrogen BondA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
  • 2 electrons is the maximum count for the ________ This is the maximum number of electrons that can occupy the ________
  • Hydrogen bonds break and re-form rapidlyThere are always enough hydrogen bonds to hold the water together, but the bonds break and re-form rapidly, allowing molecules to move relative to one another.
Despite its cohesion, water can flow because ...
  • The valence shell needs 8 electronsWithout help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
  • Has a very low pH valueHas a high hydronium ion concentrationVery acidic solutions have high hydronium concentrations, and as a result, have low pH values.
  • Hydrogen bonds break and re-form rapidlyThere are always enough hydrogen bonds to hold the water together, but the bonds break and re-form rapidly, allowing molecules to move relative to one another.
  • The solution on the right is basic relative to the solution on the leftThe solution on the right has a lower concentration of hydrogen ions relative to hydroxide ions than does the solution on the left.
By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom's charge stay close to zero?
  • It's the same reaction running backward or forwardThe buffer accepts H+ in one case; it gives off H+ in the other case
  • A water molecule can make 4 hydrogen bonds.When you heat water, much of the heat is used to break hydrogen bonds. Only the remaining heat can increase molecular motion, raising the temperature.
  • Shared electrons aren't always near oxygenOxygen keeps 6 electrons to itself. The 4 shared electrons migrate between O and the other atoms, thus contributing 4 half-charges to oxygen. This gives oxygen about 8 units of negative charge, balancing the atom's 8 protons.
  • 6 electrons
In salt, what is the nature of the bond between sodium and chlorine?
  • IonicSodium and chlorine ions are attracted to each other.
  • Carbon dioxide reacts with seawater, forming carbonic acid
  • Atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).
  • Absorption by the oceans of carbon dioxide generated by burning fossil fuels
Which of these relationships is true of an uncharged atom?
  • These atoms are isotopes.Atoms with the same atomic number and different atomic masses are referred to as isotopes.
  • The number of protons is equal to the number of electrons.In this situation the number of positive charges is equal to the number of negative charges.
  • The valence shell needs 8 electronsWithout help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
  • They consist of weak acids and weak basesBy using weak acids and bases, the buffer can absorb or give off H+, stabilizing the pH
Below is the structure of leucine, an amino acid. What type of bond is the arrow pointing to?H-N
  • Polar Covalent Bond
  • 6 electrons
  • Polar CovalentWhile oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.
  • Carbon dioxide reacts with seawater, forming carbonic acid
A solution is very acidic if it
  • Water is the solventThat's the definition of "aqueous." Water is the solvent if the solution contains more water molecules than any other kind of molecule.
  • One mole of solute per liter of solutionTo make the solution, you dissolve the solute in some solvent and then add more solvent to bring the volume up to a liter.
  • Has a very low pH valueHas a high hydronium ion concentrationVery acidic solutions have high hydronium concentrations, and as a result, have low pH values.
  • Hydrogen ions is equal to the concentration of hydroxide ionsThis is the definition of a neutral solution
Silicon is an element that is found directly underneath carbon in the periodic table. How many electrons are in the valence shell of a silicon atom?
  • 42 e- in first shell8 e- in second shell
  • Raise it to 100 times its present value.
  • Carbon dioxide reacts with seawater, forming carbonic acid
  • The H atoms in water have partial positive charges.
As pH goes up, [H+] goes ?
  • Up (acidic)
  • Down (basic)
  • Decays
  • Hydrophilic
Though you add heat, the temperature of boiling water remains constant because ...
  • It takes energy to break hydrogen bondsAt boiling, all the added heat is used to break hydrogen bonds. Free of the water mass, the departing steam carries away all the added energy, with none left over to raise the temperature.
  • Polar Covalent BondsThe hydrogen and oxygen atoms do not equally share their electrons, which results in the formation of electronegative oxygen atoms and electropositive hydrogen atoms. These are then able to interact with other water molecules to form hydrogen bonds.
  • Amino acid side chains have many carboxyl and amino groupsWhen these side chains ionize, they exert forces that affect the protein's folding. Thus, if pH isn't stabilized, the proteins will change their folding and may not function properly.
  • This is an atom of carbon, an element with 6 protons. Atomic number is the number of protons in an atom.
As pH goes down, [H+] goes ?
  • Hydrophobic
  • Polar molecules attract one anotherWater molecules cling to one another and won't part to make room for uncharged (nonpolar) molecules. There's no repulsion.
  • Water is the solventThat's the definition of "aqueous." Water is the solvent if the solution contains more water molecules than any other kind of molecule.
  • Up (acidic)
What is the chemical reaction responsible for the oceans becoming more acidic?
  • Oyster larvae cannot grow shells in acidified ocean waters
  • CovalentA covalent bond is one in which electron pairs are shared.
  • These atoms are isotopes.Atoms with the same atomic number and different atomic masses are referred to as isotopes.
  • Carbon dioxide reacts with seawater, forming carbonic acid
A 1 M solution contains ...
  • The number of protons is equal to the number of electrons.In this situation the number of positive charges is equal to the number of negative charges.
  • Polar molecules attract one anotherWater molecules cling to one another and won't part to make room for uncharged (nonpolar) molecules. There's no repulsion.
  • Is quickly reversed, giving neutral water moleculesInvolves pairs of water moleculesWater dissociates when H+ jumps from one water molecule to another. The H+ quickly jumps back.
  • One mole of solute per liter of solutionTo make the solution, you dissolve the solute in some solvent and then add more solvent to bring the volume up to a liter.
Why doesn't oil mix with water?
  • Water is the solventThat's the definition of "aqueous." Water is the solvent if the solution contains more water molecules than any other kind of molecule.
  • Have a weak acid or a weak base half ionized in waterWhen half of the molecules are ionized, there are plenty of molecules that can either absorb H+ or give off H+ when the pH is disturbed from outside.
  • Polar molecules attract one anotherWater molecules cling to one another and won't part to make room for uncharged (nonpolar) molecules. There's no repulsion.
  • PolarThe electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
Ammonia reacts with water as shown below. Which statement best explains why ammonia is considered to be a base? H₃ + H₂O ⇌ NH₄+ + OH−
  • 8 & 17The number of protons, 8, gives the atomic number. The mass number is the sum of the number of protons and neutrons, or 8 plus 9, which equals 17.
  • Rotation can occur around single bondsRotation allows groups of atoms to change position while preserving the usual bond angles around each atom.
  • Bases are compounds that remove H+ from solutionsIn becoming NH₄+, ammonia takes on H+. Removing H+ from a solution is the hallmark of a base.
  • It's the same reaction running backward or forwardThe buffer accepts H+ in one case; it gives off H+ in the other case
Substance consisting of two or more different elements combined in a fixed ratio
  • FourHydrogen
  • Compound
  • Buffer
  • 6 electrons
The term for a solution with a low pH number, such as lemon juice or vinegar, is __
  • Compound
  • 2 & 8
  • True
  • Acid
The atoms in the molecule of water are held together by which type of bond?
  • Polar Covalent BondsThe hydrogen and oxygen atoms do not equally share their electrons, which results in the formation of electronegative oxygen atoms and electropositive hydrogen atoms. These are then able to interact with other water molecules to form hydrogen bonds.
  • Carbon dioxide reacts with seawater, forming carbonic acid
  • Nonpolar Covalent Bond
  • Polar Covalent Bond
What determines the types of chemical reactions that an atom participates in?
  • The number of electrons in the outermost electron shell.An atom is least likely to participate in a reaction when its outermost shell is stable.
  • They consist of weak acids and weak basesBy using weak acids and bases, the buffer can absorb or give off H+, stabilizing the pH
  • 3The neutral atom has 7 electrons. Two electrons fill the first shell, and 5 go into the second (valence) shell. The atom needs 3 more electrons to fill the valence shell.
  • 8 & 17The number of protons, 8, gives the atomic number. The mass number is the sum of the number of protons and neutrons, or 8 plus 9, which equals 17.
A compound is an acid if it ...
  • Atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).
  • Hydrogen ions is equal to the concentration of hydroxide ionsThis is the definition of a neutral solution
  • Donates H+ to waterAcids are defined by the ability to donate H+ to water.
  • H+O-H & O bonded by Polar Covalent BondWater molecules bonded by Hydrogen Bonds
A substance that accepts H+ when they are in excess and donates H+ when their concentration drops is called a(n)
  • Heat
  • Electron-sharing
  • Buffer
  • Basic
Which answer helps to explain why carbon atoms tend to make 4 covalent bonds?
  • The H atoms in water have partial positive charges.
  • This is an atom of carbon, an element with 6 protons. Atomic number is the number of protons in an atom.
  • The valence shell needs 8 electronsWithout help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
  • Polar Groups attract one anotherPolar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
Trace elements _____.
  • OH- combines with H+ and removes it from solutionThis behavior of OH- earns the title of "base" for compounds that release OH-.
  • Is quickly reversed, giving neutral water moleculesInvolves pairs of water moleculesWater dissociates when H+ jumps from one water molecule to another. The H+ quickly jumps back.
  • Are required in very small amountsElements such as iodine, iron, and copper are needed in amounts less than 0.01%. Despite the small amounts, these elements are required for vital functions. Deficiency in iodine, for example, can produce a goiter, a large swelling in the neck.
  • The number of protons is equal to the number of electrons.In this situation the number of positive charges is equal to the number of negative charges.
An uncharged atom of boron has an atomic number of 5 and an atomic mass ofHow many electrons does boron have?
  • ElementThis is the definition of an element
  • Buffer
  • 5
  • True
An acid is a compound that donates __ to a solution
  • H-N
  • Heat
  • H+
  • None of the above
The dissociation of water
  • Results in an unequal sharing of electronsPolar covalent bonds share electrons unequally, so that one part of the molecule has a negative pole and one part has a positive pole.
  • PolarThe electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
  • Polar molecules attract one anotherWater molecules cling to one another and won't part to make room for uncharged (nonpolar) molecules. There's no repulsion.
  • Is quickly reversed, giving neutral water moleculesInvolves pairs of water moleculesWater dissociates when H+ jumps from one water molecule to another. The H+ quickly jumps back.
An ionic bond involves ________
  • Results in an unequal sharing of electronsPolar covalent bonds share electrons unequally, so that one part of the molecule has a negative pole and one part has a positive pole.
  • Has a very low pH valueHas a high hydronium ion concentrationVery acidic solutions have high hydronium concentrations, and as a result, have low pH values.
  • An attraction between ions of opposite charge.This is the definition of an ionic bond
  • Hydrogen ions is equal to the concentration of hydroxide ionsThis is the definition of a neutral solution
A phrase that applies to covalent bonding and not other kinds of bonds is ...
  • Electronegativity
  • Hydrogen bonds
  • Electron-sharing
  • FourHydrogen
When the proton number and electron number are unequal, the atom or molecule is a/an ________.
  • 3The neutral atom has 7 electrons. Two electrons fill the first shell, and 5 go into the second (valence) shell. The atom needs 3 more electrons to fill the valence shell.
  • IonWhen the proton number and electron number are unequal, the atom or molecule has a net positive or negative charge.
  • The concentrations of hydronium and hydroxide ions are equal.In a neutral solution the concentrations of hydroxide and hydronium ions must be equal.
  • Atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).
The ________ of water molecules and the hydrogen bonds between water molecules explain most of water's life-supporting properties.
  • Shellfish
  • Reactants (left side chemical equation)Products (right side chemical equation)
  • Cohesion
  • Polarity
Water has surface tension because...
  • Hydrogen bonds between surface water molecules resist being stretched.The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.
  • ElectronsElectrons are negatively charged particles. In a neutral atom, the number of electrons is equal to the number of protons. When an atom loses or gains electrons, its charge becomes positive or negative, respectively.
  • Hydrogen ions is equal to the concentration of hydroxide ionsThis is the definition of a neutral solution
  • Hydrogen bonds
Your tank of alkali fish needs a pH of 8, and the pH is 6 at present. What should you do to the H+ concentration?
  • Reduce it to 1/100 of its present valueEach pH unit is a 10-fold change in [H+]
  • Reactants (left side chemical equation)Products (right side chemical equation)
  • Atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).
  • CovalentA covalent bond is one in which electron pairs are shared.
What type of bond is joining the two hydrogen atoms?
  • Hydrogen BondA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
  • H+O-H & O bonded by Polar Covalent BondWater molecules bonded by Hydrogen Bonds
  • CovalentA covalent bond is one in which electron pairs are shared.
  • Corals and coral reefs are not able to form their hard skeletonsClams, mussels, lobsters, and shrimp are not able to form strong enough shells
An electrically neutral molecule has the formula C₃H₄O₂N. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have with other atoms in the molecule?
  • 10⁻⁵ M If you divide 10⁻¹⁴ by 10⁻⁹ M (the H+ concentration at pH 9), you get 10⁻⁵ M, the OH- concentration.
  • Carbon dioxide reacts with seawater, forming carbonic acid
  • 1A knowledge of bonding capacities makes it easier to understand the structure of molecules.
  • Electrons in two orbitalsA double bond involves two orbitals, each with a shared pair of electrons.
To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add ...
  • Structural FormulaThis kind of model is designed to show which atoms are bound to one another, but it doesn't accurately picture the sizes of atoms.
  • HydrogenOxygenMany reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.
  • PolarThe electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
  • 2 electronsThe neutral atom has 8 electrons. Two electrons fill the first shell, and 6 go into the second (valence) shell. Two more electrons would fill the valence shell.
True or False: atoms tend to avoid having a partly filled valence shell
  • True
  • False
A solution is aqueous if ...
  • A mingling of molecules and/or ionsWhen sugar dissolves in water, the sugar molecules remain intact but mingle with water molecules. When salt (NaCl) dissolves, its Na+ and Cl- ions separately mingle with water.
  • Results in an unequal sharing of electronsPolar covalent bonds share electrons unequally, so that one part of the molecule has a negative pole and one part has a positive pole.
  • Water is the solventThat's the definition of "aqueous." Water is the solvent if the solution contains more water molecules than any other kind of molecule.
  • Glycerol is the solventIn any solution, the most abundant substance is the solvent.
In a neutral solution the concentration of _____.
  • HydrogenOxygenMany reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.
  • Look for undissociated molecules of baseStrong bases dissociate completely in solution; weak bases don't.
  • Hydrogen ions is equal to the concentration of hydroxide ionsThis is the definition of a neutral solution
  • Hydrogen Bonds
Your tank of swamp fish needs a pH of 5, and the pH is 7 at present. What should you do to the H+ concentration?
  • FourThere are four electrons in the outermost electron shell
  • 10⁻⁵ M If you divide 10⁻¹⁴ by 10⁻⁹ M (the H+ concentration at pH 9), you get 10⁻⁵ M, the OH- concentration.
  • Atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).
  • Raise it to 100 times its present value.
What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
  • This is an atom of carbon, an element with 6 protons. Atomic number is the number of protons in an atom.
  • Hydrogen BondA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
  • Electrons in two orbitalsA double bond involves two orbitals, each with a shared pair of electrons.
  • The valence shell needs 8 electronsWithout help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
What conditions must be met in order for an aqueous solution to be called "neutral"?
  • These atoms are isotopes.Atoms with the same atomic number and different atomic masses are referred to as isotopes.
  • The concentrations of hydronium and hydroxide ions are equal.In a neutral solution the concentrations of hydroxide and hydronium ions must be equal.
  • Hydrogen BondA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
  • HydrogenOxygenMany reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.
How does the way a buffer stabilizes pH during addition of acid differ from the way the same buffer stabilizes pH during addition of base?
  • It's the same reaction running backward or forwardThe buffer accepts H+ in one case; it gives off H+ in the other case
  • 8 & 17The number of protons, 8, gives the atomic number. The mass number is the sum of the number of protons and neutrons, or 8 plus 9, which equals 17.
  • 2 electrons is the maximum count for the ________ This is the maximum number of electrons that can occupy the ________
  • The bone contains calcium salts, which are less reactive than the calcium ions found in blood
An atom's reactivity is determined by its _____.
  • Electrons in two orbitalsA double bond involves two orbitals, each with a shared pair of electrons.
  • 2 electrons is the maximum count for the ________ This is the maximum number of electrons that can occupy the ________
  • Hydrogen ions is equal to the concentration of hydroxide ionsThis is the definition of a neutral solution
  • Electron configurationThe fullness of the valence shell determines the pattern of covalent bonding or ionization.
A radioactive isotope is an isotope that ________
  • Down (basic)
  • Electronegative
  • Decays
  • Neutral
Thus, water absorbs or releases a great deal of ________ , helping to moderate temperatures.
  • True
  • Chemical Reaction
  • Heat
  • Decays
The term for a solution with a higher pH number, such as ammonia or bleach is
  • 2 & 8
  • Polarity
  • Cohesion
  • Basic
A single water molecule (H − O − H) is held together by ..
  • Nonpolar Covalent Bond
  • Two polar covalent bonds
  • Polar Covalent Bond
  • The properties of the atom change
An uncharged atom of boron has an atomic number of 5 and an atomic mass ofHow many protons does boron have?
  • 5The atomic number is equal to the number of protons.
  • FourThere are four electrons in the outermost electron shell
  • Carbon dioxide reacts with seawater, forming carbonic acid
  • ElementThis is the definition of an element
In molecules, C, H, O, and N atoms usually make __, __, __, and __ bonds respectively.
  • Two polar covalent bonds
  • IonicSodium and chlorine ions are attracted to each other.
  • The H atoms in water have partial positive charges.
  • 4, 1, 2, 3 H: 1O: 2N: 3C: 4
What name is given to the bond between water molecules?
  • Rotation can occur around single bondsRotation allows groups of atoms to change position while preserving the usual bond angles around each atom.
  • CovalentA covalent bond is one in which electron pairs are shared.
  • Hydrogen BondA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
  • Polar CovalentWhile oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.
How are oyster larvae affected by ocean acidification?
  • Hydrogen BondA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
  • H+O-H & O bonded by Polar Covalent BondWater molecules bonded by Hydrogen Bonds
  • Oyster larvae cannot grow shells in acidified ocean waters
  • Electrons in two orbitalsA double bond involves two orbitals, each with a shared pair of electrons.
Generally, what determines the number and kinds of chemical bonds an element can make and the chemical reactivity of an element?
  • Bases are compounds that remove H+ from solutionsIn becoming NH₄+, ammonia takes on H+. Removing H+ from a solution is the hallmark of a base.
  • Shared electrons aren't always near oxygenOxygen keeps 6 electrons to itself. The 4 shared electrons migrate between O and the other atoms, thus contributing 4 half-charges to oxygen. This gives oxygen about 8 units of negative charge, balancing the atom's 8 protons.
  • ElectronsElectrons are negatively charged particles. In a neutral atom, the number of electrons is equal to the number of protons. When an atom loses or gains electrons, its charge becomes positive or negative, respectively.
  • The number of electrons in its outer shellOnly electrons are directly involved in the interactions between atoms, and the number of electrons in the outer shell determines the chemical behavior of the atom.
What is part of the explanation for water's high cohesion?
  • Amino acid side chains have many carboxyl and amino groupsWhen these side chains ionize, they exert forces that affect the protein's folding. Thus, if pH isn't stabilized, the proteins will change their folding and may not function properly.
  • Oxygen has four valence orbitalsOxygen is much more electronegative than hydrogenThe electronegativity difference creates charges that make hydrogen bonds possible, and the four outer orbitals permit water to make four hydrogen bonds. The result is a three-dimensional network of bonds between water molecules.
  • Hydrogen BondA hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.
  • Hydrogen bonds between surface water molecules resist being stretched.The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.
An atom's atomic number isIts valence is most likely ...
  • The concentrations of hydronium and hydroxide ions are equal.In a neutral solution the concentrations of hydroxide and hydronium ions must be equal.
  • 8 & 17The number of protons, 8, gives the atomic number. The mass number is the sum of the number of protons and neutrons, or 8 plus 9, which equals 17.
  • The solution on the right is basic relative to the solution on the leftThe solution on the right has a lower concentration of hydrogen ions relative to hydroxide ions than does the solution on the left.
  • 3The neutral atom has 7 electrons. Two electrons fill the first shell, and 5 go into the second (valence) shell. The atom needs 3 more electrons to fill the valence shell.
0:0:1



Answered

Not Answered

Not Visited
Correct : 0
Incorrect : 0