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?

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Solution

## (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 $×$ 2) = 0.4 Mass of sodium hydrogen carbonate required to produce 0.2 moles of sodium carbonate = Number of moles $×$ Molecular mass of NaHCO3 = 0.4 $×$ 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 $×$ Molar volume at STP = 0.4 $×$ 22.4 = 8.96 L

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