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A sample of washing soda has the following composition by mass: - Na₂CO₃: molecular mass 106.0, mass percentage 84.8 - NaHCO₃: molecular mass 84.0, mass percentage 8.4 - NaCl: molecular mass 58.5, mass percentage 6.8 If 1 kg of this sample is treated completely with excess HCl, the amount of carbon dioxide released will be:

1. 9 mol of CO₂
2. 16 mol of CO₂
3. 17 mol of CO₂
4. 18 mol of CO₂

Correct answer: 9 mol of CO₂

Solution

Na2CO3 848/106 = 8 mol -> 8 CO2; NaHCO3 84/84 = 1 mol -> 1 CO2; NaCl gives none. Total 9 mol CO2. Stored 17 is wrong.

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