How many grams of MgO must be produced to cause an enthalpy change of -96 kJ?

Question

2 Mg(s) + O2(g) 2 MgO(s) H = -1204 kJ

Answer 1

If the reaction 2 Mg(s) + O2(g) -> 2 MgO(s) has an enthalpy of -1204kJ, then the enthalpy is -602 kJ/mol of MgO.

Step 1: Find the molar mass.
MgO has a molar mass of 24.3 + 16 = 40.3 g/mol

Step 2: Convert kJ/mol to kJ/g
-602 kJ/mol / 40.3 g/mol = -14.938 kJ/g

Step 3: Use the equation: H = H/g * m to find the mass.
-96 kJ = -14.938 kJ/g * x g
x = -96 / -14.938 = 6.42 g MgO