When a strip of magnesium reacts completely with excess hydrochloric acid in of…

CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics

Problem

When a strip of magnesium reacts completely with excess hydrochloric acid in

100.0\,\text{mL}

of aqueous solution at an initial temperature of

25.0^{\circ}\text{C}

, the temperature rises to

31.4^{\circ}\text{C}

. (Density of the solution is

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

and its specific heat capacity is

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

.) The molar enthalpy of the reaction is

\Delta H_{\text{rxn}} = -462\,\text{kJ mol}^{-1}

with respect to magnesium. Approximately how many moles of magnesium reacted? (a)

1.2 \times 10^{-2}\,\text{mol}

(b)

5.8 \times 10^{-3}\,\text{mol}

(c)

2.9 \times 10^{-3}\,\text{mol}

(d)

5.8 \times 10^{-4}\,\text{mol}