If the heat of combustion for a specific compound is - 1170.0kJ / mol and its molar mass is 96.79g / mol, how many grams of this compound must you burn to release 485.50 kJ of heat?

Answer 1

Using dimensional analysis, we have...

485.50 kJ x 1 mol/1170.0 kJ x 96.79 g/mol = g

Doing the math, we get 40.16 g of compound (4 sig. figs.)

To check this answer, we can find the heat produced by 40.16 g of a compound with molar mass 96.79 g/mol

40.16 g x 1 mol/96.79 g = 0.41496 moles of compound

0.41496 moles x 1170.0 kJ/mol = 485.50 kJ of heat which agrees with the question being asked.