Class 9 Practice – Level 3 - Set 1 – Atoms and Molecules.

Total questions: 15

Which of the following statements about isotopes is incorrect?

Topic: Basic Concepts of Atoms and Molecules

Isotopes have the same number of protons but different numbers of neutrons.

Isotopes have different atomic numbers.

Isotopes have similar chemical properties.

Isotopes have different mass numbers.

None

Calculate the number of atoms in 0.25 moles of carbon atoms.

Topic: Basic Concepts of Atoms and Molecules

$ \displaystyle {6.022\text{ }\times \text{ }{{{10}}^{{23}}}}$

$ \displaystyle {1.505\text{ }\times \text{ }{{{10}}^{{23}}}}$

$ \displaystyle {3.011\text{ }\times \text{ }{{{10}}^{{23}}}}$

$ \displaystyle {7.527\text{ }\times \text{ }{{{10}}^{{23}}}}$

None

Which of the following molecules has a linear shape?

Topic: Basic Concepts of Atoms and Molecules

$\displaystyle {{{H}_{2}}O}$

$\displaystyle {C{{O}_{2}}}$

$\displaystyle {C{{H}_{4}}}$

$\displaystyle {N{{H}_{3}}}$

None

In the formation of a compound, 10 grams of A combine with 20 grams of B. According to the Law of Definite Proportions, how much of B will combine with 40 grams of A?

Topic: Laws of Chemical Combination

40 grams

60 grams

80 grams

20 grams

None

Who is credited with the discovery of the Law of Multiple Proportions?

Topic: Laws of Chemical Combination

Antoine Lavoisier

John Dalton

Joseph Proust

Dmitri Mendeleev

None

Which experiment led to the discovery of the nucleus in an atom?

Topic: Atomic Structure

Thomson's cathode ray experiment

Rutherford's gold foil experiment

Millikan's oil drop experiment

Bohr's hydrogen spectrum experiment

None

What is the significance of the discovery of the neutron?

Topic: Atomic Structure

It explained the stability of the nucleus.

It led to the discovery of isotopes.

It confirmed the existence of subatomic particles.

It explained the behaviour of electrons.

None

Which isotope of uranium is used as fuel in nuclear reactors?

Topic: Isotopes

Uranium-235

Uranium-238

Uranium-239

Uranium-240

None

What is the common application of the isotope Carbon-14?

Topic: Isotopes

Cancer treatment

Radiocarbon dating

Radiation therapy

Power generation

None

10.

Calculate the number of moles in 50 grams of methane $ \displaystyle {C{{H}_{4}}}$ .

Topic: Mole Concept

2.5 moles

3.125 moles

4.25 moles

5.125 moles

None

11.

How many molecules are there in 0.75 moles of oxygen gas $ \displaystyle \left( {{{O}_{2}}} \right)$ ?

Topic: Mole Concept

$ \displaystyle {3.011\text{ }\times \text{ }{{{10}}^{{23}}}}$

$ \displaystyle {4.516\text{ }\times \text{ }{{{10}}^{{23}}}}$

$ \displaystyle {6.022\text{ }\times \text{ }{{{10}}^{{23}}}}$

$ \displaystyle {1.505\text{ }\times \text{ }{{{10}}^{{23}}}}$

None

12.

What is the molecular mass of potassium nitrate $ \displaystyle \left( {KN{{O}_{3}}} \right)$ ?

Topic: Molecular Mass and Mole Concept

101 g/mol

102 g/mol

103 g/mol

104 g/mol

None

13.

How many grams are there in 0.4 moles of calcium carbonate $ \displaystyle \left( {CaC{{O}_{3}}} \right)$ ?

Topic: Molecular Mass and Mole Concept

40 g

50 g

60 g

70 g

None

14.

What is the empirical formula of a compound with the molecular formula $ \displaystyle {{C}_{4}}{{H}_{{10}}}$ ?

Topic: Empirical and Molecular Formulas

$ \displaystyle {CH}$

$\displaystyle {{{C}_{2}}{{H}_{5}}}$

$ \displaystyle {{{C}_{4}}{{H}_{5}}}$

$ \displaystyle {{{C}_{2}}{{H}_{4}}}$

None

15.

A compound has an empirical formula of $ \displaystyle C{{H}_{2}}$ and a molar mass of 56 g/mol. What is its molecular formula?

Topic: Empirical and Molecular Formulas

$ \displaystyle {C{{H}_{2}}}$

$ \displaystyle {{{C}_{2}}{{H}_{4}}}$

$ \displaystyle {{{C}_{3}}{{H}_{6}}}$

$ \displaystyle {{{C}_{4}}{{H}_{8}}}$

None

1 out of 15

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Class 9 Practice – Level 3 - Set 1 – Atoms and Molecules.

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