Hydrogen peroxide decomposes to water and oxygen at constant pressure by the following reaction:
2H₂O₂(l) → 2H₂O(l) + O₂(g) ΔH = -196 kJ
Calculate the value of q (kJ) in this exothermic reaction when 4.00 g of hydrogen peroxide decomposes at constant pressure?

Question

Quizplus · Accepted Answer

The molar mass of H₂O₂ is 34.01 g/mol. 4.00 g of H₂O₂ is 4.00 g / 34.01 g/mol = 0.1176 mol. The reaction releases 196 kJ for 2 moles of H₂O₂, so for 0.1176 mol, q = (196 kJ / 2 mol) * 0.1176 mol = -11.5 kJ.

Hydrogen Peroxide Decomposes to Water and Oxygen at Constant Pressure