When 1 mol of methane is burned at constant pressure, −890 kj/mol of energy is released as heat. if a 4.19 g sample of methane is burned at constant pressure, what will be the value of ∆h? (hint: convert the grams of methane to moles. also make sure your answer has the correct sign for an exothermic process.) answer in units of kj.

∆H = -233 kJ

Explanation:

Methane is CH₄, the molar mass are: 12 g/mol of C + 4x1 g/mol of H = 16 g/mol.

The number of moles is the mass divided by the molar mass:

n = 4.19/16

n = 0.261875 mol

1 mol of CH₄ -890 kJ

0.261875 mol x

By a direct simple three rule:

x = -233 kJ

∆H is negative because it's an exothermic reaction, and the system lost heat.