Inside an insulated vessel

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

Problem

Inside an insulated vessel, two phase changes occur simultaneously: •

10.0\,\text{g}

of steam at

100\,^{\circ}\!\text{C}

condenses to liquid water. •

150.0\,\text{g}

of liquid water at

0\,^{\circ}\!\text{C}

freezes to ice. Given

\Delta H_{\text{vap}}(\text{H}_2\text{O}) = 40.7\,\text{kJ mol}^{-1}

and

\Delta H_{\text{fus}}(\text{H}_2\text{O}) = 6.01\,\text{kJ mol}^{-1}

, what is the net heat change

q_{\text{net}}

for the system? (Molar mass of water

=18.02\,\text{g mol}^{-1}

.) (a)

+27.4\,\text{kJ}

(b)

-72.7\,\text{kJ}

(c)

+72.7\,\text{kJ}

(d)

-50.1\,\text{kJ}