Question

To make use of an ionic hydrate for storing solar energy, you place 510.0 kg of sodium sulfate decahydrate on your house roof. Assuming complete reaction and 100% efficiency of heat transfer, how much heat (in kJ) is released to your house at night? Note that sodium sulfate decahydrate will transfer 354 kJ/mol.

Answer 1

Here we have to get the amount of heat will generate by 510.0 kg of sodium sulfate decahydrate at night assuming complete reaction and 100% efficiency of heat transfer.

510.0 kg of sodium sulfate decahydrate will produce 5.603 × 10⁵ kJ of heat energy.  

The molecular weight of sodium sulfate decahydrate (H₂₀Na₂O₁₄S) 322.186 g/mol.

Thus 510.0 kg of H₂₀Na₂O₁₄S is equivalent to $\frac{510000g}{322.186g/mol}$ = 1582.936 mol of H₂₀Na₂O₁₄S.

Now per mole of H₂₀Na₂O₁₄S will transfer 354 kJ heat.

Thus 1582.936 mol will transfer 1582.936 × 354 kJ =  5.603×10⁵ kJ of heat.

Henceforth, 510.0 kg of sodium sulfate decahydrate will produce 5.603 × 10⁵ kJ of heat energy.