A 0.1375-g of solid mg is burned with a heat capacity of 3024 J/C. The temperature increases by 1.126 C. Calculate the heat given off by the burning Mg in kJ/g and in kJ/mol.

Answer 1

I'm going to assume that this was performed in a bomb calorimeter with a heat capacity of 3024 J/ºC (something not mentioned in the original question). That being the case, we have the following:

q = C_cal x ∆T

q = heat = ?

C_cal = calorimeter constant = 3024 J/º

∆T = change in temperature = 1.126º

q = (3024 J/º)(1.126º)

q = 3405 J

To express this in kJ /g we have the following calculation:

3405 J / 0.1375 g x 1 kJ / 1000 J = 24.76 kJ / g

To express this in kJ / mole, we have the following calculation:

24.76 kJ / g x 24.32 g Mg / mol = 602.2 kJ / mole