How much energy (in kilojoules) is released when 15.3 g of steam at 115C is condensed to give liquid water at 75C? The heat of vaporization of liquid water is 40.67 kJ/mol, and the molar heat capacity is 75.3 J/ (k*mol) for the liquid and 33.6 J / (k*mol) for the vapor.
I don't get this at all!!
2007-01-31 06:10:45 · 2 answers · asked by samaireh d 1 in Science & Mathematics ➔ Chemistry
You have 15.3/18 = 0.85 moles of H2O
Steam cooling: 33.6 * (115-100) * 0.85 = 428 kJ
Condensing: 40.7 * 0.85 = 34.6 kJ
Water cooling: 75.3 * (100-75) * 0.85 = 1600 kJ
Total = 2060 kJ to 3 sigfigs
2007-01-31 06:19:50 · answer #1 · answered by gebobs 6 · 0⤊ 0⤋
gebobs is right.
you cool the steam, then condense the steam at constant temperature, then cool the liquid.
change in energy = moles x heat capacity x temperature difference for the two liquid steps
and change in energy = moles x heat of vaporization
for the condensation step.
and moles = mass / molecular weight = 15.3 / 18 = 0.85 moles
2007-01-31 14:24:42 · answer #2 · answered by Dr W 7 · 0⤊ 0⤋