Question

Which statement about the following reaction is correct?

Answer 1

Answer: 32.6 kJ of heat is released for every 0.5 mole of CaO that reacts.

Explanation:

Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and $\Delta H$ for the reaction comes out to be negative.

$CaO(s)+H2O(l)\rightarrow Ca(OH)_2(s)$ $\Delta H =-65.2 kJ$

The given reaction shows that 1 mole of $CaO$ reacts to release 65.2 kJ of energy.

Thus if 1 mole of  $CaO$ release = 65.2 kJ of energy.

Thus 0.5 moles of  $CaO$ release = $\frac{65.2}{1}\times 0.5=32.6kJ$ of energy.

Thus 32.6 kJ of heat is released for every 0.5 mole of CaO that reacts.

Answer 2

Since delta H is negative, that means that heat is released, so that eliminates two answers. Since the second response says that twice the delta H value is released for every mole of H2O, that mean that there would have to be a coefficient of 2 in front of H2O for that statement to be true. The next response says that half of the delta H value is released when half of CaO reacts. Since this response is consistent in that if an entire mole of CaO reacts, then the full delta H value would released. So the third response is correct