Question

Methanol(MM=32.04g/mole) is sometimes used as fuel for race cars, since methanol fires are easily extinguished with water. the energy content o methanol is investigated in a high-quality calorimeter for which the heat capacity is known to be 4.5Kj/C. When 17.62g of liquid of methanol is burned in the calorimeter. its temperature rises from 21 to 99.03celicus. Find the enthalpy for the combustion of methanol.

I used the equation q = ms(Tfinal - Tinitial) and i got an answer of 5394.09kJ. Did i do it correctly?

Answer 1

If you used that equation, you are not going to get the right answer.

Heat of combustion is often tabulated in kJ/mole OR kJ/gram

Lets do it in moles.

Heatcombustion*molesMethanol=heatcapacity*(Tf-Ti)

heatcombustion*17.62/32.04=4.5kJ/C*(78.03C)

solve for heat combustion in J/mole

Answer 2

okay i knew i was doing something wrong when i used that formula. Thanks! I got an answer of 639.59 kJ/mol, it seems about right.