CBSE Questions for Class 9 Chemistry Atoms And Molecules Quiz 4 - MCQExams.com

A neutral atom of an element has a nucleus with a nuclear charge 13 times and mass 27 times that of hydrogen nucleus. What is the ratio of electrons to protons in its stable positively charged ion?
  • 27 : 13
  • 10 : 19
  • 10 : 13
  • 10 : 14
When hydrogen burns in oxygen, _________ is produced.
  • water
  • hydrogen peroxide
  • both A and B
  • none of these
The percentage by mole of $${ NO }_{ 2 }$$ in a mixture of $${ NO }_{ 2 }(g)$$ and $$NO(g)$$ having average molecular mass 34 is :
  • 25%
  • 20%
  • 40%
  • 75%
The symbol for SI unit of mole is:
  • mol
  • mole
  • M
  • $$m$$
$$N_2O$$ is heavier than $$O_2$$.
  • True
  • False
Various theories were put forward to study  the nature of atom. The main postulates of Dalton's atomic theory are:
  • Dalton's atomic theory proposed that all matter was composed of atoms.
  • Dalton's atomic theory proposed that all matter was composed of molecules.
  • All atoms of an element are identical.
  • The atoms of different elements vary in size and mass.
According to Dalton's atomic theory, the smallest particle from which matter is made up of is called as:
  • atom
  • ion
  • electron
  • molecule
$$1$$ amu is equal to $$1.66\times 10^{-24}$$ g.
  • True
  • False
The number of moles of '$$X$$ ' atoms in $$93$$ gm of 'X' are:
(Molecular Weight of $$X =31$$ g/mole)
  • $$3 $$
  • $$3.5 $$
  • $$4$$
  • $$2$$
The number of atoms in $$60$$ g of neon$$[Ne]$$ are:
(Molar mass of $$Ne=20$$ g/mole)
  • $$6 \times 6.022 \times 10 ^{23} $$ atoms
  • $$2 \times 6.022 \times 10 ^{23} $$ atoms
  • $$5 \times 6.022 \times 10 ^{23} $$ atoms
  • $$3 \times 6.022 \times 10 ^{23} $$ atoms
What mass of $$Na$$ will contain $$6.023 \times  10^{23}$$ number of atoms?
  • $$23$$ g
  • $$46$$ g
  • $$6.023$$ g
  • $$11.5$$ g
Atomic number (Z) of a neutral atom and mass number (A) of an atom are equal to: 
(Here n = number of neutrons and p = number of protons):
  • Z = n and A = n+p
  • Z = e and A = n+e
  • Z = p and A = n+p
  • Z = n and A = p+e
The number of potassium atoms present in $$117$$ g of potassium sample (Molecular Weight $$= 39$$ g/mole) is:
  • $$9 \times 6.023 \times 10 ^{23} $$ atoms
  • $$7 \times 6.023 \times 10 ^{23} $$ atoms
  • $$4 \times 6.023 \times 10 ^{23} $$ atoms
  • $$3 \times 6.023 \times 10 ^{23} $$ atoms
A/An______ is the smallest particle of a substance which can take part in a chemical reaction.
  • atom
  • molecule
  • both A and B
  • none of the above
The mass of one molecule of compound $${C}_{60}{H}_{122}$$ is :
  • $$1.3\times {10}^{-20}g$$
  • $$5.01\times {10}^{-21}g$$
  • $$3.72\times {10}^{-23}g$$
  • $$1.4\times {10}^{-21}g$$
The number of nitrogen atoms in $$21$$ g of nitrogen are:
(Molecular Weight of Nitrogen $$=14$$ g/mole)
  • $$0.75$$$$N_A$$
  • $$1.5$$$$N_A$$
  • $$21$$$$N_A$$
  • $$14$$$$N_A$$
Which of the following is a suitable example for illustrating the law of conservation of mass? (Atomic mass of O = 16 u; H = 1 u)
  • 18g of water is formed by the combination of 16g oxygen with 2g of hydrogen.
  • 18g of water in liquid state is obtained by heating 18g of ice.
  • 18g of water is completely converted into vapour state on heating.
  • 18g of water freezes at $$4^{o}C$$ to give same mass of ice.
The molecular mass of $$CuSO_4.5H_2O$$ is:
(Atomic mass of $$Cu$$ $$=$$ 63.5, $$H$$ $$=$$ 1, $$O$$ $$=$$ 16, $$S$$ $$=$$ 32)
  • 233.5 gm/mole
  • 249.5 gm/mole
  • 251.5 gm/mole
  • 247.5 gm/mole
Which has a higher mass : 1 mole of $$CO_2$$ or 1 mole of $$CO?$$ (Mass of $$C=12,$$  Mass of $$O=16$$)
  • $$CO_2$$
  • $$CO$$
  • Both $$CO_2$$ and $$CO$$ have same mass
  • None of the above
Two elements always combine together in a fixed ratio by weight.
  • True
  • False
Consider the following statements:
(a) Molecular mass of $$CH_3OH$$ is $$32\ u.$$
(b) In $$NH_3$$, the ratio of $$N$$ and $$H$$ by mass is $$14: 3.$$
(c) The formula mass of $$CaCl_2$$ is $$ 111\ u.$$
(d) Isotopes have same mass number.

Which of the above statements are correct?
  • $$\text {(a) and (c)}$$
  • $$\text {(a), (b) and (d)}$$
  • $$\text {(a), (b) and (c)}$$
  • $$\text {(a), (c) and (d)}$$
The molecular mass of $$(NH_4)_2CO_3$$ is:
Given atomic mass of H = 1, O = 16, C = 12, N = 14.
  • 96 gm/mole
  • 98 gm/mole
  • 94 gm/mole
  • 80 gm/mole
Sodium chloride ($$NaCl$$) reacts with silver nitrate ($$AgNO_3$$) to produce silver chloride ($$AgCl$$) and sodium nitrate ($$NaNO_3$$). The law which satisfies this equation is ___________________ .
  • conservation of mass
  • conservation of energy
  • newton's law
  • dalton's law
Two chemical species $$X$$ and $$Y$$ combine together to form a product $$P$$ which contains both $$X$$ and $$Y$$

                                                     $$X  +  Y  \rightarrow  P$$

$$X$$ and $$Y$$ cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species $$X, Y$$ and $$P$$ are correct?

(i)    $$P$$ is a compound
(ii)   $$X$$ and $$Y$$ are compounds
(iii)  $$X$$ and $$Y$$ are elements
(iv)  $$P$$ has a fixed composition
  • (i), (ii) and (iii)
  • (i), (ii) and (iv)
  • (ii), (iii) and (iv)
  • (i), (iii) and (iv)
State whether the given statement is true or false.

An atom is electrically neutral though it contains charged particles.
  • True
  • False
$$1.2\, \times\, 10^{24}$$ atoms of iron weighs  ______ grams.
  • $$90$$
  • $$111.5$$
  • $$80$$
  • $$70$$
An element A (atomic weight $$=12$$) and B (atomic weight $$=35.5$$) combines to form a compound X. If $$4$$ mol of B combines with $$1$$ mol of A to give $$1$$ mol of X. The weight of $$1$$ mol of X would be :
  • 47.5 g
  • 74.0 g
  • 154.0 g
  • 148.8 g
The number of electrons and protons are always equal in all atoms.
  • True
  • False
Which of the following options contains only elements?
  • Air, water, oxygen
  • Hydrogen, oxygen, brass
  • Air, water, iron
  • Calcium, sulphur, carbon
State True or False.

There is no difference between one mole and one gram molecule.
  • True
  • False
State True or False.
Mass of reactants is always equal to the mass of the products. (Don't consider nuclear reaction)
  • True
  • False
Law of conservation of mass was put forward by :
  • Lavoisier
  • Dalton
  • Priestly
  • Thomson
A compound was found to contain $$5.37\ \%$$ of Nitrogen. What is the minimum molecular weight of the compound?
  • 26.07 g
  • 2.607
  • 260.7
  • None
Atomic mass of an element is:
  • actual mass of one atom of the element
  • average mass of an atom of different atoms of the element
  • always a whole number
  • None of these
All samples of carbon dioxide contain carbon and oxygen in the mass ratio of $$3 : 8$$. This is in agreement with the law of :
  • conservation of mass
  • constant proportion
  • multiple proportions
  • gaseous volumes
An organic compound contains $$4$$% sulphur. Its minimum molecular weight is :
  • 200
  • 400
  • 800
  • 1600
Which of the following is not a compound?
  • Oxygen
  • Water
  • Sugar
  • Common salt
The smallest particle of a substance (element or compound) which has the properties of that substance and can exist independently is called a ..............
  • Molecule
  • Atom
  • Nucleus
  • Neutrons
.............. is the smallest unit of an element that maintains the properties of that element.
  • electron
  • atom
  • proton
  • ions
Calculate the molecular mass of $$H_2O$$ (Water)
  • $$18$$
  • $$36$$
  • $$20$$
  • $$16$$
An atom which is deficient of electrons is called a  ________ .
  • positive ion
  • proton
  • negative ion
  • none of these
Molecules are the components of:
  • Solutions
  • Gases
  • Solids
  • All of the above
State True or False.
The smallest particle of an element is molecule.
  • True
  • False
When hydrogen and oxygen combine to form water, they form:
  • an unstable compound
  • a stable mixture
  • an unstable mixture
  • an extremely stable compound
3 g of a hydrocarbon on combustion in excess of oxygen produces 8.8 g of $$CO_2$$ and 5.4 g of $$H_2O$$. 

The data illustrates the law of :
  • Conservation of mass
  • Multiple proportions
  • Constant proportions
  • None of the above
The weights of two elements which combines with one another are in the ratio of their:
  • atomic weight
  • molecular weight
  • equivalent weight
  • none of the above
Weight of oxygen in $$32.2$$ g $$\displaystyle Na_{2}SO_{4}$$.$$\displaystyle 10H_{2}O$$ is:
  • 20.8 gm
  • 22.4 gm
  • 2.24 gm
  • 2.08 gm
Modern atomic mass scale is based on the mass of:
  • $$H - 1$$
  • $$C - 12$$
  • $$C - 14$$
  • $$C - 16$$
Weight of oxygen in $$Fe_2O_3$$ and FeO is in the ratio of :
  • $$3 : 2$$
  • $$1 : 2$$
  • $$2 : 1$$
  • $$3 : 1$$
The percentage of copper and oxygen in a sample of CuO obtained from different methods were found to be same. This proves the law of :
  • Constant proportion
  • Multiple proportion
  • Reciprocal proportion
  • None of these
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