Chemistry 5070 · O Level · The mole and the Avogadro constant

The mole and the Avogadro constant — practice question

Each of the reactions shown generates hydrogen. Which reaction gives the largest volume of hydrogen, measured at room temperature and pressure?

  • A$1.4\,\text{g}$ carbon reacts with excess steam. $\text{C}(s)+\text{H}_2\text{O}(g)\rightarrow\text{H}_2(g)+\text{CO}(g)$
  • B$2.4\,\text{g}$ calcium hydride, $\text{CaH}_2$, reacts with excess water. $\text{CaH}_2(s)+2\text{H}_2\text{O}(l)\rightarrow\text{Ca(OH)}_2(aq)+2\text{H}_2(g)$
  • C$4.0\,\text{g}$ calcium reacts with excess dilute hydrochloric acid. $\text{Ca}(s)+2\text{HCl}(aq)\rightarrow\text{CaCl}_2(aq)+\text{H}_2(g)$
  • D$50\,\text{cm}^3$ of $2.0\,\text{mol dm}^{-3}$ sulfuric acid reacts with excess zinc. $\text{Zn}(s)+\text{H}_2\text{SO}_4(aq)\rightarrow\text{ZnSO}_4(aq)+\text{H}_2(g)$

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