Question

The equations given below relate to the manufacture of sodium carbonate (Molecular weight of Na₂CO₃ = 106).
NaCl + NH₃ + CO₂ + H₂O $\stackrel{}{\to }$ NaHCO₃ + NH₄Cl
2NaHCO₃ $\stackrel{}{\to }$ Na₂CO₃ + H₂O + CO₂
Questions (a) and (b) are based on the production of 21.2 g of sodium carbonate.
(a) What mass of sodium hydrogen carbonate must be heated to give 21.2 g of sodium carbonate (Molecular weight of NaHCO₃ = 84)?
(b) To produce the mass of sodium hydrogen carbonate, calculate what volume of carbon dioxide, measured at STP would be required?

Answer 1

(a) According to the balanced chemical equation, two moles of sodium hydrogen carbonate must be heated to give one mole of sodium carbonate.
Number of moles of sodium carbonate in 21.2 g = $\frac{21.2}{106}=0.2$
Number of moles of sodium hydrogen carbonate required to produce 0.2 moles of sodium carbonate = (0.2 $\times$ 2) = 0.4
Mass of sodium hydrogen carbonate required to produce 0.2 moles of sodium carbonate = Number of moles $\times$ Molecular mass of NaHCO₃ = 0.4 $\times$ 84 = 33.6 g

(b) According to the balanced chemical equation, one mole of CO₂ is required to produce one mole of sodium hydrogen carbonate.
Number of moles of CO₂ required to produce 0.4 moles of sodium hydrogen carbonate = 0.4
Volume of 0.4 moles of CO₂ at STP = Number of moles $\times$ Molar volume at STP
= 0.4 $\times$ 22.4 = 8.96 L