A laboratory sample consists of magnesium metal and inert by mass

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

Problem

15.0\,\text{g}

laboratory sample consists of

40.0\%

magnesium metal and

60.0\%

inert

\text{NaCl}

by mass. The magnesium reacts completely with excess hydrochloric acid according to

\text{Mg}(s)+2\text{HCl}(aq)\rightarrow\text{MgCl}_2(aq)+\text{H}_2(g)\;\;\;\Delta H=-4.62\times10^{2}\,\text{kJ per mole of }\text{Mg}

How much heat is released to the surroundings when the sample is added to the acid? (a)

-4.62\times10^{2}\,\text{kJ}

(b)

-2.86\times10^{2}\,\text{kJ}

(c)

-1.14\times10^{2}\,\text{kJ}

(d)

+1.14\times10^{2}\,\text{kJ}