CBSE Questions for Class 9 Chemistry Atoms And Molecules Quiz 7 - MCQExams.com

When mass is enclosed in a system and no transfer of material and energy is allowed in or out, it's _____ will never change.
  • quality
  • quantity
  • temperature
  • shape
During any chemical change, the total mass of the products is equal to the total mass of reactants. This is a statement according to:
  • Law of conservation of mass
  • Law of constant composition
  • Law of multiple proportion
  • Law of reciprocal proportion
$$AgNO_3+NaCl\rightarrow AgCl+NaNO_3$$. In this reaction, mass of $$AgNO_3$$ and $$NaCl$$ is equal to the mass of $$AgCl$$ and $$NaNO_3$$. Then this chemical reaction satisfies:
  • Law of constant composition
  • Law of conservation of mass
  • Gay Lussac's law
  • Law of multiple proportion
When magnesium is burnt in air, the weight of magnesium :
  • increases
  • decreases
  • remains same
  • Depends on the atmosphere
Magnesium + Oxygen $$\longrightarrow$$     Magnesium Oxide + Oxygen
 48.6 g        +     50.0 g $$\longrightarrow$$     80.6 g                   +      ? 

Predict the mass of oxygen that will be left over after the reaction of 48.6 grams of magnesium with 50.0 grams of oxygen. 
  • 20.6
  • 19.6
  • 18
  • 17.6
The chemical equation is balanced to satisfy one of the following laws in chemical reactions. This law is known as the:
  • law of conservation of mass.
  • law of multiple proportions
  • law of chemical equilibrium.
  • none of these
The matter is neither created nor destroyed during any physical or chemical change. This statement is of the :
  • Law of constant proportion
  • Law of conservation of mass
  • Law of reciprocal proportion
  • Law of multiple proportion
Calculate the mass (in grams) of one molecule of $$CH_{3}COOH$$. 
(Molar mass of $$CH_{3}COOH = 60.06\ g/ mol$$)
  • $$9.97\times 10^{-23}$$
  • $$60.06$$
  • $$9.97\times 10^{23}$$
  • None of above
What are the merits of Dalton's atomic theory?
  • Explains laws of chemical combination
  • Explains the law of conservation of mass
  • Both A and B
  • Atoms can not be rearranged, combined or separated in a chemical reaction.
In a compound, the ratio of the atoms or element by mass remains always the same irrespective of :
  • temperature
  • nature of compound
  • source of compound
  • size of compound
A solution of copper oxide was prepared by heating, igniting and precipitation. Which of the following method will give higher ratio of copper oxide?
  • Heating
  • Precipitation
  • Ignition
  • All of the above will give the same ratio
Dalton’s atomic theory was based on:
  • Law of chemical combination
  • Mass theory
  • Periodic table
  • None of the above
______ are the smallest unit of matter that can take part in a chemical reaction.
  • Molecules
  • Compounds
  • Atoms
  • Electrons
If the ratio of the atoms by mass is altered then:
  • new compound formed
  • same compounds are formed
  • no reaction takes place
  • state of compounds are changed
Combustion of a piece of paper to form ash, water vapour and carbon dioxide follows law of conservation of mass.
  • True
  • False
The ratio of mass of nitrogen and oxygen in nitric oxide is:
  • $$7:16$$
  • $$1:8$$
  • $$7:8$$
  • $$7:15$$
The concept of atom based on experimental observation first came from:
  • Dalton's atomic theory
  • Law of conservation of mass
  • Law of mass theory
  • Law of chemical combination
Which of the following is polyatomic element?
  • Sulphur
  • Phosphorous
  • Argon
  • Helium
What is the molecular mass of $$C_2H_4?$$ 
  • $$26$$
  • $$14$$
  • $$28$$
  • $$16$$
Formula unit mass of magnesium chloride is :
  • 94
  • 95
  • 96
  • 24
Which of the following is true with respect to law of conservation of matter?
  • It is also called as law of conservation of mass.
  • Mass of products in a chemical reaction is equal to the mass of reactants.
  • Matter is not perfectly conserved
  • All of the above
Dalton's atomic theory was not accepted fully :
  • when atoms combine it must be presumed to be a binary one, unless some cause appear to the contrary.
  • when elements react, their atoms sometimes combine in more than one simple, whole-number ratio.
  • elements are characterized by the mass of their atoms.
  • None of the above
Atoms of different elements combine in:
  • unequal ratios.
  • prime number ratios.
  • equal ratios.
  • whole number ratios.
Find the mass of $$4.12\times 10^{24}$$ molecules of $$NH_3$$?
  • $$110\ g$$
  • $$116.3\ g$$
  • $$120\ g$$
  • $$100\ g$$

Atomic mass of which of the following element is $$24$$?
  • Magnesium
  • Sodium
  • Chlorine
  • Sulphur
Who believed that atoms could not be split?
  • Thomson
  • Rutherford
  • Dalton
  • Both A and B
Who postulated that matter is made up of very small particles in 430 BC?
  • Democritus
  • Aristotle
  • Dalton
  • Robert Brown
When two molecules of hydrogen react with one molecule of oxygen, the mass of reactants is $$36$$, what is the mass of products?
  • $$18$$
  • $$36$$
  • $$9$$
  • $$32$$
Who proposed the earliest views on the shapes and connectivity of atoms?
  • Leucippus
  • Rutherford
  • Thomson
  • Both B and C
J.J. Thomson discovered _________ at the end of 19th century.
  • Electrons
  • Nuclei
  • Atoms
  • Molecules
The theory of Democritus state that:
  • everything is composed of "atoms", which are physically, but not geometrically, indivisible
  • between atoms, there lies empty space
  • there are an infinite number of atoms
  • All of the above
Which of the following structural feature of an atom was proposed by Rutherford?
  • The positively charged particle is called a proton.
  • The size of the nucleus is very small as compared to the size of the atom. 
  • An atom consists of a positively charged sphere and the electrons are embedded in it.
  • All of above
Which law is not applicable for a nuclear reaction where large amount of energy is released? 
  • Law of conservation of mass
  • Law of definite proportion
  • Law of multiple proportion
  • Avagrado's law
Formula unit mass for $$K_2CO_3$$ is :
  • 140u
  • 138u
  • 120u
  • 125u
A formula unit indicates :
  • the highest whole number ratio of ions in a compound.
  • only the lowest whole number ratio of uncharged molecules in a compound.
  • the lowest whole number ratio of ions in a compound.
  • both A and B.
The formula unit mass of a substance is the:
  • sum of the atomic masses of all atoms in a formula unit of a compound
  • relative atomic masses of atoms
  • double the numerical value of the atomic mass
  • None of above
Molecules made up of two or more elements are called:
  • ions
  • compounds
  • mixture
  • both a and c
Which of the following element is represented by the chemical symbol $$P$$ ?
  • Sulphur
  • Phosphorus
  • Oxygen
  • Hydrogen
Which of the following is not a property of a molecule?
  • Molecules of any given substance are similar.
  • Molecules are represented by chemical formula.
  • The properties of a substance are the properties of the molecule.
  • None of above.
A molecule is _________ .
  • Positive
  • Negative
  • Neutral
  • Both A and C
Formula unit mass is used for :
  • molecules
  • ionic compound
  • uncharged compounds
  • all of above
Which of the following is not a molecule?
  • $$O$$
  • $$O_2$$
  • $$CO_2$$
  • $$N_2$$
Which of the following is Dalton's symbol for carbon?
  • None of above
Formula mass unit of $$Na_2CO_3.10H_2O$$ is :
  • 290
  • 286
  • 180.02
  • 105.97
Formula unit mass of $$ ZnO$$ is :
  • $$85$$
  • $$90$$
  • $$81$$
  • $$89$$
What is the formula mass of $$Ba(HSO_3)_2$$?
Atomic mass of Ba  is 137 u
  • 299 u
  • 250 u
  • 290 u
  • 260 u
The formula unit mass of $$CuSO_4.5H_2O$$ is
  • 159.62
  • 90.10
  • 249.72
  • 240
 Kanad called the tiniest of tiny particles of matter as:
  • Parman
  • Parmounu
  • Anu
  • Parmanu
One atomic mass is equal to
  • $$1.66\times10^{-27}$$ g
  • $$1.66\times10^{-24}$$ g
  • $$1.66\times10^{-23}$$ g
  • $$1.66\times10^{-25}$$ g
Formula unit mass for $$(NH_{4})_{2}SO_{4}$$ is :
  • 142 u
  • 129 u
  • 137 u
  • 132 u
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