Stuck on chemistry problem due tonight

Question

How many grams of oxygen are required to produce 70 kJ of heat during melting? The heat of fusion of oxygen is 0.44 kJ /mole. Round to a whole number

Answer 1

The equation to use is Q = HOF x moles O2, where Q is the quantity of heat absorbed by the process, HOF is the heat of fusion. We are given the heat required (70 kj) and the HOF (0.44 kj/mole).

Solving the equation for mole O2 = Q / HOF = 70 kj / 0.44 kj/mole = 159.1 moles O2 needed. This can be converted to grams by multiplying the molecular mass of O2 (32 g) by the number of moles calculated. Gms O2 = 159.1 moles x 32 g/mole = 5091 g O2.