Chapter 3: Atoms and Molecules

a) Molar mass of CO2 = 12 + 2 x 16 = 12 + 32 = 44 g mol^-1

5 moles of CO2 have mass = 44 x 5 = 220 g

Similarly, molar mass of H2O = 2x 1 + 16 = 18 g mol ^-1

5 moles of H2O have mass =18 x 5 = 90 g

It is verified that 5 moles of CO₂ and 5 moles of H₂O are not same.

b) Number of moles = w/atomic weight

Atomic weight of Ca= 40 amu

Number of moles in 240g Ca metal 240/ 40 = 6

Number of moles in 240g of Mg metal 240/ 24 = 10

Atomic weight of Mg = 24amu

Ratio 6:10

a) CaCO3

Ca: C : O × 3

40 : 12 : 16 × 3

40: 12 : 48

10 : 3 : 12

(b) MgCl2

Mg : Cl × 2

24: 35.5 × 2

24: 71

(c) H2SO4

H x 2 : S : O × 4

2: 32 : 16 × 4

2 : 32 : 64

1: 16: 32

(d) C2H5OH

C × 2 : H × 6 : O

12 × 2 : 1 × 6 : 16

24 : 6 : 16

12 : 3 : 8

(e) NH3

N : H × 3

14 : 1 × 3

14: 3

(f) Ca(OH)2

Ca : O × 2 : H × 2

40 : 16 × 2 : 1 × 2

40 : 32 : 2

20 : 16 : 1

Solution coming soon.