# Atoms and Molecules Worksheet-2

Atoms and Molecules Worksheet-2

1. Calculate the mass of 0.72 gram molecule of carbon dioxide (CO2)?

A. 33 g                B. 30 g                C. 31.68 g          D. 29 g

1. Calculate the number of moles of iron in a sample containing 1022 atoms of iron.

A. 0.0199 mol                               B. 0.01 mol

C. 1.015 mol                                   D. 0.009 mol

1. Calculate the number of moles in the following :

(i) 46 g of Na    (ii) 60 g of Ca

Given gram atomic mass of (i) Na = 23 g (ii) Ca = 40 g.

A. (i)2 mol     (ii) 1.5 mol

B. (i)1.5 mol  (ii) 1.5 mol

C. (i)2 mol     (ii) 2 mol

D. (i)2 mol     (ii) 1 mol

1. Calculate the mass of 6.022 × 1023 molecules of O2.

(Given : Gram atomic mass of oxygen = 16 g, Gram molecular mass of oxygen (O2) = 32 g)

A. 16g                 B. 32g                 C. 8g

1. What is the mass in ‘u’ of 4 moles of aluminium atoms? (Atomic mass Al = 27u)

A. 27 u                B. 108 u             C. 81 u

1. What is the mass in ‘u’ of 10 moles of sodium sulphate? (Atomic mass of Na = 23 u, S = 32 u, O = 16 u)

A. 142 u              B. 140 u              C. 1420 u           D. 1400

1. Calculate the weight of carbon monoxide having the same number of oxygen atoms as are present in 22 g of carbon dioxide.

A. 28 g                B. 44g                 C. 22 g                D. 11g

1. How many atoms are present in one gram atomic mass of a substance?

A. 6.022 × 1023 atoms                 B. 3.022 × 1023 atoms

C. 6.022 × 1030 atoms                 D. 6.022 × 1028 atoms

1. What is the mass of two moles of oxygen atoms?

A. 16                    B. 32                   C. 48                   D. 64

1. How many moles are present in :

(i)  10 g of Ca.    (ii) 2.3 g of Na

A. (i) 0.5 mole    (ii) 0.1 mole

B. (i) 0.25 mole  (ii) 0.5 mole

C. (i) 0.75 mole  (ii) 0.1 mole

D. (i) 0.25 mole  (ii) 0.01 mole

1. C

Explanation:

Molecular mass of CO2 = atomic mass of C + 2 × atomic mass of O

= (12u + 2 ×) 16u = 44u

gram molecular mass of CO2 = 44g

1 gram molecular of CO2 = 44g

0.72 gram molecular of CO2 1. A

Explanation:  1. A

Explanation: (ii) 46 g of Na (iii) 60 g of Ca 1. B

Explanation: 6.022 × 1023 molecules of oxygen (O2)

I mole of a substance contains Avogadro number of particles.

Step I: Calculation of number of gram moles of oxygen.  Step II: Calculation of mass of oxygen (O2) molecules.

Mass of oxygen (O2) molecules = Gram molecular mass of oxygen × No. of gram moles of oxygen.

= (32 g) × 1 = 32g.

1. B

Explanation: 4 moles of aluminium atoms

Mass of 1 mole of aluminium (Al) atoms = 27 u

∴ Mass of 4 moles of aluminium (Al) atoms 1. C

Explanation: Mass of 1 moles of sodium sulphate (Na2SO4) = 142 u

Mass of 10 moles of sodium sulphate (Na2SO4) = 1420 u

1. A

Explanation: (i). Calculation of the number of oxygen atoms in 22 g of carbon dioxide (CO2)

Molar mass of CO2 = 12 + 2 × 16 = 44u

1mole of a substance = 1 Gram molecular mass of the substance.

44 g of CO2 = 1 mol The number of oxygen atoms in 1 mole of CO2 = 2 × N0

= 2 × 6.022 × 1023

∴ the number of oxygen atoms 0.5 mole of CO2 = 2 × 6.022 × 1023 × 0.5

= 6.022 × 1023 atoms.

(ii). Calculation of weight of carbon monoxide (CO)

6.022 × 1023 atoms of oxygen are present in 6.022 × 1023 molecules of carbon monoxide (CO).

According to mole concept 1 mole of a substance contains Avogadro number of particles.

6.022 × 1023 molecules of CO have mass = Molar mass of CO = 12 + 16 = 28 g.

1. A

Explanation: One gram atomic mass of a substance contains Avogadro number of atoms i.e. 6.022 × 1023

1. B

Explanation: Gram atomic mass of one mole of oxygen atoms =  16 g

∴ Mass of 2 moles of oxygen atoms = 32 g

1. C

Explanation: 1 gram atomic mass of calcium  =  40 g = 1 mole

10 g of calcium = 0.25 mole

1 gram atomic mass of sodium = 23 g = 1 mole

2.3 g = 0.1 mole