Question

The equations given below relate to the manufacture of sodium carbonate (Molecular weight of Na₂CO₃ = 106).

1. \[\ce{NaCl + NH3 + CO2 + H2O -> NaHCO3 + NH4Cl}\]
2. \[\ce{2NaHCO3 -> Na2CO3 + H2O + CO2}\]

Equations (1) and (2) are based on the production of 21.2 g of sodium carbonate.

1. What mass of sodium hydrogen carbonate must be heated to give 21.2 g of sodium carbonate?
2. To produce the mass of sodium hydrogen carbonate calculated in (a), what volume of carbon dioxide, measured at STP, would be required?

Answer 1

(a) \[\ce{\underset{2 × 84 = 168}{2NaHCO3} ≡ \underset{106}{Na2CO3}}\]

For obtaining 106 g of Na₂CO₃ amount of NaHCO₃ heated = 168 g.

∴ For obtaining 21.2 g of Na₂CO₃ amount of NaHCO₃ heated = `168/106 xx 21.2`

= 33.6 g

(b) \[\ce{\underset{84 g}{NaHCO3} ≡ \underset{22.4 litre}{CO2}}\]

84 g of NaHCO₃ at STP ≡ 22.4 litre of CO₂

33.6 g of NaHCO₃ at STP ≡ `22.4/84 xx 33.6`

= 8.96 litre

= 8960 ml