[Catherina]

Question:  A calorimeter has a heat capacity of 40.00 kJ/cels. Complete combustion of 1.00 g of hydrogen in this calorimeter causes a temperature increase of 3.54celsius. Calculate the molar enthalpy of combustion for hydrogen from this evidence.

My answer:

c= 40.00 kJ/celsius
/\t= 3.54

qcal = 40 * 3.54 = 141.6 kJ

Hcomb = qcal/n

n=1/1.01 = 0.99

Hcomb = 141.6/0.99 = 143.03 kJ/mol.

The corrected answer I have has the n= 1/2.02 , so the final answer of the equation is -286 kJ/mol.

Why is the n of Hydrogen being doubled.. is it because Hydrogen's are found in two's?    I thought it was the mass (1 gram) divided by the molar mass (1.01).   

[Padfoot]

Why is the n of Hydrogen being doubled.. is it because Hydrogen's are found in two's?   

Yep, hydrogen exists as a diatomic molecule.  This would make the molar mass 2.02 (2 x 1.01) 

[Catherina]

Thank you!