Question

What is the molar heat of combustion of methanol, CH3OH, if combustion of 1.00g of methanol causes a temperature of 3.68 degrees Celsius in a bomb calorimeter that has a heat capacity of 6.43kJ/degrees Celsius?

Answer 1

if 1g of methanol causes a 3.68 degree change, then find molar mass of methanol. 1 mole methanol = 32.05g, so 32.05 times as much energy will be released by a mole and the temp will change 32.05 times as much. 32.05 x 3.68 = 117.944 degree C change per mole of methanol.

If it takes 6.43 Kj to raise it one degree C, and the temp rose 117.944 degrees C, just multiply 6.43 by 117.944. The answer is 758.37992 Kj, and since it is exothermic and 3 sig figs, the answer is
-758Kj/mol