Question

Verify by calculating that 

(a) 5 moles of CO₂ and 5 moles of H₂O do not have the same mass. 

(b) 240 g of calcium and 240 g magnesium elements have a mole ratio of 3:5.

Answer 1

(a) CO₂ has molar mass               = 44g mol^–1 

5 moles of CO₂ have molar mass = 44 × 5 

                                                     = 220 g 

H₂O has molar mass                   = 18 g mol^–1 

5 moles of H₂O have mass         = 18 × 5 g 

                                                   = 90 g 

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

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

Ratio 6:10 

         3: 5