Need help! Standard enthalpy change for balanced reactions

Question

Decomposition of hydrogen peroxide is exothermic with (change in enthalpy= 192kj). Im asking for help on how to calculate how much heat energy will be released when 3.5 grams of Hydrogen peroxide decomposes.

1. 2H2O2(aq)-> 2H2O(I) +O2(g)

Answer 1

How many moles of H₂O₂ is 3.5 g?

3.5 g H₂O₂ x 1 mol H₂O₂ / 34 g = 0.1029 moles H₂O₂

According to the balanced equation, 2 moles of H₂O₂ produces a change in enthalpy of 192 kJ. Using dimensional analysis, we solve for change in enthalpy for 0.1029 moles H₂O₂....

0.1029 moles x 192 kJ/2 moles = 9.88 kJ = -9.9 kJ (to 2 significant figures) <negative sign since exothermic>