A coffee-cup calorimeter contains of water and has a calorimeter constant (heat…

CHEMISTRY · Single correct · AP · Chemistry · Thermochemistry · Thermochemistry

Problem

A coffee-cup calorimeter contains

100.0\,\text{g}

of water and has a calorimeter constant (heat capacity) of

145\,\text{J}\,^{\circ}\!\text{C}^{-1}

. When

1.25\,\text{g}

\mathrm{LiCl(s)}

is added, the temperature of the water and calorimeter rises from

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

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

. The accepted literature value for

\Delta H_{\text{solution}}

\mathrm{LiCl(s)}

-37.0\,\text{kJ}\,\text{mol}^{-1}

. Which pair of experimental values is most consistent with the data? (a)

\Delta H_{\text{solution}} = +35\,\text{kJ}\,\text{mol}^{-1};\;\text{percent error} = 4.6\%

(b)

\Delta H_{\text{solution}} = -26\,\text{kJ}\,\text{mol}^{-1};\;\text{percent error} = 29\%

(c)

\Delta H_{\text{solution}} = -35\,\text{kJ}\,\text{mol}^{-1};\;\text{percent error} = 4.6\%

(d)

\Delta H_{\text{solution}} = -35\,\text{kJ}\,\text{mol}^{-1};\;\text{percent error} = 9.2\%