Question

Given the following thermochemical equation, calculate the heat (in kJ) involved in decomposing 18.0 g of
water to give one mole of H2 (g).

Answer 1

You do not provide the thermochemical formation or the heat of reaction. It should have been part of your problem statement.

18.0 g of H2O is one mole. The answer will be the heat of formation of H2O, expressed as Kcal or kJ per mole. The decomposition reaction is endothermic.

My textbook says the heat of formation of H2O is -57.8 kcal/mol. The minus sign means the formation of H2O from H2 and O2 is exothermic. For your answer, forget the minus sign and you will have the heat required to decompose.

Since that want it in kJ, you will have to multiply by 4.18 kJ/kcal

Answer 2

The specific heat of aluminum is 0.0215 cal/g °C. If a 4.55 g sample of
aluminum absorbs 2.55 cal of energy, by how much will the temperature of
the sample change?

Answer 3

0.249

Answer 4

26.1