A student places a strip of magnesium with mass into of aqueous hydrochloric acid at

CHEMISTRY · Subjective · A Level · Chemistry · Energetics · Energetics

Problem

A student places a strip of magnesium with mass

0.125\,\text{g}

into

150\,\text{g}

of aqueous hydrochloric acid at

25.0^{\circ}\text{C}

. The solution temperature rises to

28.8^{\circ}\text{C}

. Assume the specific heat capacity of the solution is

4.18\,\text{J}\,\text{g}^{-1}\,^{\circ}\text{C}^{-1}

and the density is

1.00\,\text{g}\,\text{mL}^{-1}

. Determine the molar enthalpy change,

\Delta H_{\text{rxn}}

, for the reaction

\text{Mg}(s)+2\text{HCl}(aq)\rightarrow\text{MgCl}_2(aq)+\text{H}_2(g)

\text{kJ}\,\text{mol}^{-1}

of magnesium.