CBSE Questions for Class 9 Chemistry Atoms And Molecules Quiz 3 - MCQExams.com

The mass of one oxygen molecule is:
  • $$2.656\times 10^{-23}\ gm$$
  • $$5.312\times 10^{-23}\ gm$$
  • $$1.66\times 10^{24}\ gm$$
  • $$32\ gm$$
The formula and molecular mass of common salt is :
  • $$NaCl, 58.5$$
  • $$MgCl_2, 46$$
  • $$CaCl_2, 62$$
  • $$FeCl_3, 54$$
The formula and molecular mass of ethanol is:
  • $$C_3H_6O = 34 g mol^{-1}$$
  • $$C_2H_6O_2 = 62 g mol^{-1}$$
  • $$C_2H_5O = 45 g mol^{-1}$$
  • $$C_2H_6O = 46 g mol^{-1}$$
Which of the following contain maximum number of molecules?
  • 1g $$CO_2$$
  • 1g $$N_2$$
  • 1g $$H_2$$
  • 1g $$CH_4$$
The number of atoms present in $$10$$ gms of $$CaCO_{3}$$ is:
  • $$5N_{A}$$
  • $$0.5N_{A}$$
  • $$5$$
  • $$N_{A}$$
Assertion: 1 mole $$O_{3} (ozone)=N$$ molecule of $$O_{3} (ozone)=3N$$ atoms of $$O (oxygen)=48g$$

Reason: A mole is the amount of matter that contains as many as objects as the number of atoms exactly in 12 g C-12 ($$N$$ = Avogadro number).
  • Assertion is correct but Reason is incorrect.
  • Assertion is incorrect but Reason is correct.
  • Both Assertion and Reason are correct and Reason is correct explanation of Assertion
  • Both Assertion and Reason are correct but Reason is not correct explanation of Assertion
Mass of one atom of oxygen is:
  • $$\frac {16}{6.023 \times 10^{23}}g$$
  • $$ \frac {32}{6.023 \times 10^{23}}g$$
  • $$ \frac {1}{6.023 \times 10^{23}}g$$
  • $$8\ u$$
Cation and anion present (if any) in $$CH_3COONa$$ are :
  • Cation; $$CH_3 COO^-$$ Anion; $$Na^+$$
  • Anion; $$CH_3 COO^-$$ Cation; $$Na^+$$
  • Cation; $$CH_3 COO^{2-}$$ Anion; $$Na^+$$
  • Anion; $$CH_3 COO^{2-}$$ Cation; $$Na^+$$
Which of the following statements is not true about an atom?
  • Atoms are not able to exist independently.
  • Atoms are the basic units from which molecules and ions are formed.
  • Atoms are always neutral in nature.
  • Atoms aggregate in large numbers to form the matter that we can see, feel or touch.
Which has maximum number of atoms?
  • 24 g of C (12)
  • 56 g of Fe (56)
  • 27 g of Al (27)
  • 108 g of Ag (108)
Which of the following compounds contains maximum number of atoms? 
  • 18gm of $$H_2O$$
  • 18gm of $$O_2$$
  • 18gm of $$CO_2$$
  • 18gm of $$CH_4$$
The number of atoms in 0.1 mol of a triatomic gas is:
  • 6.026 x 10$$^{22}$$
  • 1.806 x 10$$^{23}$$
  • 3.600 x 10$$^{23}$$
  • 1.800 x 10$$^{22}$$
Avogadro's number is ?
  • $$6.023 \times 10^{23}$$
  • $$6.066 \times 10^{-19}$$
  • $$6.032 \times 10^{24}$$
  • $$6.203 \times 10^{18}$$
Which of the following would weigh the highest?
  • 0.2 mole of sucrose $$(C_{12} H_{22} O_{11})$$
  • 2 moles of carbon dioxide $$(CO_2)$$
  • 2 moles of calcium carbonate $$(CaCO_3)$$
  • 10 moles of water $$(H_2O)$$
  • Assertion and reason both are correct statements and reason is correct explanation for assertion.
  • Assertion and reason both are correct statements but reason is not correct explanation for assertion.
  • Assertion is correct statement but reason is wrong statement.
  • Assertion is wrong statement but reason is correct statement.
The mass of one steel screw is 4.11gm. Find the mass of one mole of these steel screws. 
  • $$2.475 \times 10^{21} kg$$
  • $$3.56 \times 10^{21} kg$$
  • $$4.2 \times 10^{21} kg$$
  • $$4.2 \times 10^{20} kg$$
A sample of vitamic C is known to contain $$2.58 \times10^{24}$$ oxygen atoms. How many moles of oxygen atoms are present in the sample?
  • 2.28 moles
  • 2.14 moles
  • 1 moles
  • 4.28 moles
Which has more number of atoms: $$100$$ g of $$N_2$$ or $$100$$ g of $$NH_3$$?
  • $$NH_3$$
  • $$N_2$$
  • Both have same number of atoms
  • Cannot be determined
The formula unit mass of $$Ca_3 (PO_4)_2$$ is :
  • $$360$$
  • $$240$$
  • $$118$$
  • $$310$$
Raunak took 5 moles of carbon atoms in a container and Krish also took 5 moles of sodium atoms in another container of same weight. Whose container has more number of atoms?
  • Raunak
  • Krish
  • Both have same
  • None of these
The visible universe is estimated to contain $$10^{22}$$ stars. How many moles of stars are present in the visible universe?
  • $$6.023 \times 10^{23}$$ moles
  • $$6.023$$ moles
  • $$1.5$$ moles
  • $$0.0166$$ moles
Cations and anions present (if any) in $$NH_4NO_3$$ are :
  • Anions: $$NO_{3}^{2-}$$ Cations: $$NH_{4}^{3+}$$
  • Cations: $$NO_{3}^{-}$$ Anions: $$NH_{4}^{2+}$$
  • Cations: $$NO_{3}^{-}$$ Anions: $$NH_{4}^{+}$$
  • Anions: $$NO_{3}^{-}$$ Cations: $$NH_{4}^{+}$$
Calculate the molecular mass of the caustic potash :
  • $$K_2OH$$ $$ = 95 g mol^{1}$$
  • $$ KOH  = 56 g mol^{1}$$
  • $$K(OH)_2$$ $$ = 73 g mol^{1}$$
  • $$ KOH  = 58 g mol^{1}$$
A sample of pure water, irrespective of source, contains 88.89% oxygen and 11.11% hydrogen
by mass. The data supports the:
  • law of conservation of mass
  • law of constant composition
  • law of multiple proportion
  • law of reciprocal proportion
The molecular weight of calcium carbonate $$CaCO_{3}$$ is:
  • 80
  • 90
  • 100
  • 110
One a.m.u. or one 'u' is equal to :
  • $$1.66053892 10^{-27} kg$$
  • $$1.66053892 10^{-29} kg$$
  • $$1.23457656 10^{-27} kg$$
  • $$1.23457656 10^{-29} kg$$
Combined atoms have more:
  • unstability
  • stability
  • attraction
  • name of these
Which of the following obeys the law of constant proportions in their formation?
  • Mixtures
  • Compounds
  • Elements
  • Colloids
The number of atoms in one mole of a substance is equal to ................ ?
  • Avagadro number
  • Mass number
  • Both (a) and (b) above
  • Density 
Rahul dropped 150 g of marble chips into 1 kg of HCl solution containing 0.1 of its weight of pure acid. The mass of marble chips that remained undissolved will approximately be:
  • 6.50 g
  • 13 g.
  • 26 g.
  • 15 g.
Identify the correct statement(s) from the following.
  • The ion having a positive charge on it, is known as electro-positive ion.
  • The ion having a negative charge on it, is known as electro-negative ion.
  • Simple ion is an ion which contains one or more atoms of the same element.
  • Compound ion is an ion which contains two or more atoms of different elements.
The weight of $$100$$ molecules of each of the following substances is:
(a) Chlorine gas
(b) Calcium oxide
  • (a) $$6.022\times 10^{-23}$$ g   (b) $$9.29\times 10^{-21}$$ g
  • (a) $$11.78\times 10^{-23}$$ g   (b) $$9.29\times 10^{-23}$$ g
  • (a) $$23.96\times 10^{-21}$$ g   (b) $$9.29\times 10^{-23}$$ g
  • (a) $$11.78\times 10^{-21}$$ g   (b) $$9.29\times 10^{-21}$$ g
Total number of atoms in 20 g of calcium carbonate is ________.
  • none of the above
  • $$N_A$$
  • $$ 5N_A$$
  • $$ \dfrac {1}{5}N_A$$
The ratio by mass of sulphur and oxygen in $$SO_2$$ is:
  • 1 : 2
  • 2 : 1
  • 1 : 1
  • 1 : 4
A substance formed by the reaction of hydrogen and oxygen is called a/an:
  • element
  • compound
  • solution
  • mixture
Atoms have a tendency to form molecules to attain stability.
  • True
  • False
Smallest particles of matter which cannot be further divided are called:
  • molecules
  • objects
  • atoms
  • none of these
Hydrogen, oxygen and carbon dioxide are taken in containers of $$2\:l$$ volume each. Compare the number of molecules of the three gases under same conditions of temperature and pressure.
  • Hydrogen > oxygen > carbon dioxide
  • Hydrogen = oxygen > carbon dioxide
  • Hydrogen > oxygen = carbon dioxide
  • All have equal
The modern atomic mass unit is based on the mass of :
  • C-12 isotope
  • hydrogen
  • oxygen
  • nitrogen
$$1 \,amu$$ is equal to $$1.66 \times 10^{-24}$$ g. 
  • True
  • False
A magnesium ion has a net positive charge while the magnesium atom has no charge.
  • True
  • False
Barium chloride reacts with sodium sulphate to form Barium sulphate and sodium chloride. Then, according to the law of conservation of mass:
  • the total mass of reactants, barium chloride, and sodium sulphate taken is greater than the total mass of products, barium sulphate, sodium chloride formed
  • the total mass of reactants, barium chloride, and sodium sulphate is less than the total mass of products, barium sulphate, and sodium chloride
  • the total mass of the reactants is equal to the total mass of products
  • none of the above
Which law states that the total mass of the reactants is equal to the total mass of the products in a chemical reaction?
  • Law of constant proportions
  • Law of conservation of energy
  • Law of conservation of mass
  • Law of multiple proportions
Assertion : Formula mass (in grams) of magnesium chloride has $$12.044\times 10^{23}$$ magnesium ions. Reason : One formula mass of an ionic compound has $$6.022\times 10^{23}$$ ions of each type.
  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
  • Assertion is correct but Reason is incorrect
  • Assertion is incorrect but Reason is correct
  • Both assertion and reason are incorrect.
What is the mass (in grams) of $$3$$ moles of $$N$$ atom?
  • $$28$$ g
  • $$42$$ g
  • $$84$$ g
  • $$14$$ g
$$1$$ g of $$^{12}C$$ contains $$6.022\times 10^{23}$$ atoms of Carbon. 
  • True
  • False
2$$Na$$ represent 2 molecules of sodium.
  • True
  • False
Plumbous ion is represented as $$Pb^{+4}$$.
  • True
  • False
Chemical compounds are formed to have constant composition irrespective of their
  • Method of formation (or) Source
  • Conditions for formation
  • Substances taken for formation
  • Time of formation
What is the mass of one atom of $$C-12$$ in grams?
  • 1.992$$\displaystyle \times 10^{-23}$$ gm
  • 1.989$$\displaystyle \times 10^{-23}$$ gm
  • 1.892$$\displaystyle \times 10^{-23}$$ gm
  • 1.965$$\displaystyle \times 10^{-23}$$ gm
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