Class 9 Practice Level 2 – Set 2 – Atoms and Molecules

Total questions: 25

A compound has an empirical formula of CH and a molar mass of 78 g/mol. What is its molecular formula?

Topic: Empirical and Molecular Formulas

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

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

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

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

None

In the reaction $ \displaystyle {{N}_{2}}+\text{ }3{{H}_{2}}\to \text{ }2N{{H}_{3}}$, , how many moles of hydrogen are required to produce 1 mole of ammonia?

Topic: Chemical Reactions and Equations

1.5 moles

2 moles

3 moles

4 moles

None

What is the product formed when magnesium reacts with hydrochloric acid?

Topic: Chemical Reactions and Equations

Magnesium hydroxide

Magnesium chloride

Magnesium carbonate

Magnesium nitrate

None

How many moles are there in 24 grams of oxygen gas ($\displaystyle {O}_{2}$)?

Topic: Mole Concept

0.75 moles

1 mole

1.5 moles

2 moles

None

What is the volume of 2 moles of nitrogen gas $ \displaystyle \left( {{{N}_{2}}} \right)$ at STP?

Topic: Mole Concept

11.2 L

22.4 L

44.8 L

56.0 L

None

How many neutrons are there in an isotope of potassium-40 (K-40) if the atomic number of potassium is 19?

Topic: Atomic Structure

None

What is the electronic configuration of an element with atomic number 12?

Topic: Atomic Structure

$ \displaystyle {1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}}$

$ \displaystyle {1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{1}}}$

$ \displaystyle {1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{p}^{2}}}$

$ \displaystyle {1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}}$

None

Which isotope of carbon is used in radiocarbon dating?

Topic: Isotopes

Carbon-12

Carbon-13

Carbon-14

Carbon-15

None

How many protons, neutrons, and electrons are present in an atom of uranium-235 (U-235)?

Topic: Isotopes

92 protons, 143 neutrons, 92 electrons

92 protons, 146 neutrons, 92 electrons

92 protons, 143 neutrons, 91 electrons

92 protons, 146 neutrons, 91 electrons

None

10.

What is the molecular mass of sulfuric acid?

Topic: Molecular Mass and Mole Concept

96 g/mol

98 g/mol

100 g/mol

102 g/mol

None

11.

How many grams are there in 0.2 moles of potassium permanganate $\displaystyle \left( {KMn{{O}_{4}}} \right)$ ?

Topic: Molecular Mass and Mole Concept

25.6 g

31.6 g

27.2 g

30.4 g

None

12.

What is the chemical formula for calcium phosphate?

Topic: Chemical Formulas

$ \displaystyle {CaP{{O}_{4}}}$

$\displaystyle {C{{a}_{3}}{{{\left( {P{{O}_{4}}} \right)}}_{2}}}$

$ \displaystyle C{{a}_{2}}{{\left( {P{{O}_{4}}} \right)}_{3}}$

$ \displaystyle Ca{{\left( {P{{O}_{4}}} \right)}_{2}}$

None

13.

How many atoms are present in one molecule of ammonium sulphate $ \displaystyle {{{{\left( {N{{H}_{4}}} \right)}}_{2}}S{{O}_{4}}}$ ?

Topic: Chemical Formulas

None

14.

Which element has the highest electronegativity?

Topic: Periodic Table and Elements

Fluorine

Oxygen

Nitrogen

Chlorine

None

15.

What is the group number of the noble gases in the periodic table?

Topic: Periodic Table and Elements

Group 16

Group 17

Group 18

Group 19

None

16.

Which of the following statements is true about the law of conservation of mass?

Topic: Basic Concepts of Atoms and Molecules

Mass is neither created nor destroyed in a chemical reaction.

Mass can be created but not destroyed in a chemical reaction.

Mass can be destroyed but not created in a chemical reaction.

Mass changes during a chemical reaction.

None

17.

Which subatomic particle was discovered by J.J. Thomson?

Topic: Atomic Structure

Proton

Neutron

Electron

Positron

None

18.

An atom has 19 protons and 20 neutrons. What is its atomic number and mass number?

Topic: Atomic Structure

Atomic number = 19, Mass number = 39

Atomic number = 20, Mass number = 39

Atomic number = 39, Mass number = 19

Atomic number = 19, Mass number = 20

None

19.

Calculate the number of atoms in 2 moles of sulphur (S).

Topic: Atomic Structure

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

$ \displaystyle 1.204\times {{10}^{{24}}}$ atoms

$ \displaystyle 2.408\times {{10}^{{24}}}$ atoms

$ \displaystyle 3.012\times {{10}^{{24}}}$ atoms

None

20.

In the reaction 2Na + $ \displaystyle \text{C}{{\text{l}}_{\text{2}}}$ → 2NaCl, how many grams of NaCl are produced from 46 grams of sodium?

Topic: Stoichiometry

117 g

58 g

80 g

100 g

None

21.

How many moles of oxygen are required to completely react with 4 moles of aluminium in the reaction $ \displaystyle \text{4AI+3}{{\text{O}}_{2}}\to 2\text{A}{{\text{I}}_{\text{2}}}{{\text{O}}_{\text{3}}}?$

Topic: Stoichiometry

2 moles

3 moles

4 moles

6 moles

None

22.

A compound has a molecular formula $ \displaystyle {{\text{C}}_{\text{4}}}{{\text{H}}_{{\text{10}}}}\text{.}$ What is its empirical formula?

Topic: Empirical and Molecular Formulas

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

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

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

$ \displaystyle {{\text{C}}_{\text{4}}}{{\text{H}}_{{\text{10}}}}\text{.}$

None

23.

In the reaction $ \displaystyle \text{Zn+}{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\to \text{ZnS}{{\text{O}}_{\text{4}}}\text{+}{{\text{H}}_{\text{2}}}$, how many grams of hydrogen gas are produced when 65 grams of zinc react completely?

Topic: Chemical Reactions and Equations

2.0 g

1.0 g

4.0 g

6.0 g

None

24.

An atom has an atomic number of 15 and a mass number of 31. How many neutrons does it have?

Topic: Atomic Number and Mass Number

None

25.

Which of the following elements is located in Group 2 of the periodic table?

Topic: Periodic Table and Elements

Sodium

Magnesium

Aluminium

Silicon

None

1 out of 25

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Class 9 Practice Level 2 – Set 2 – Atoms and Molecules

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