The molar enthalpies of vaporization at the normal boiling points are for ethanol…

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

Problem

The molar enthalpies of vaporization at the normal boiling points are

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

for ethanol (molar mass

46.1\,\text{g\,mol}^{-1}

) and

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

for acetone (molar mass

58.1\,\text{g\,mol}^{-1}

). For a

25\,\text{g}

sample of each liquid at its boiling point, which statement is correct? (a) Vaporizing

25\text{ g}

of ethanol requires the same amount of heat as vaporizing

25\text{ g}

of acetone. (b) No heat is required for either sample because vaporization at the boiling point occurs isothermally. (c) Vaporizing

25\text{ g}

of ethanol requires more heat than vaporizing

25\text{ g}

of acetone. (d) Vaporizing

25\text{ g}

of acetone requires more heat than vaporizing

25\text{ g}

of ethanol.