Chemistry 0620 · IGCSE · The mole and the Avogadro constant

The mole and the Avogadro constant — practice question

The chemical equation for the thermal decomposition of sodium hydrogencarbonate is given as: $2\text{NaHCO}_3 \rightarrow \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2$. The $M_r$ of sodium hydrogencarbonate, $\text{NaHCO}_3$, is $84$. The $M_r$ of sodium carbonate, $\text{Na}_2\text{CO}_3$, is $106$. During an experiment, $2.1\,\text{g}$ of sodium hydrogencarbonate is heated, although only part of it decomposes. Every bit of the carbon dioxide is gathered and then measured at room temperature and pressure. The overall volume of carbon dioxide made is $0.21\,\text{dm}^3$. At room temperature and pressure, the volume occupied by $1$ mole of a gas is $24\,\text{dm}^3$. Which statement is correct?

  • AThe mass of sodium carbonate produced is $0.93\,\text{g}$.
  • BThe mass of sodium carbonate produced is $1.33\,\text{g}$.
  • CThe percentage yield of carbon dioxide is $10\%$.
  • DThe percentage yield of carbon dioxide is $35\%$.

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