The thermochemical equation describing the heat change in the decomposition of limestone,CaCO₃,is given by CaCO₃(s)+ 176 kJ → CaO(s)+ CO₂(g).What is the heat change that accompanies the decomposition of 25.0 g of limestone?

Question

Quizplus · Accepted Answer

The given thermochemical equation involves the decomposition of 1 mole of limestone with a heat change of 176 kJ. This means that the heat change is proportional to the number of moles of limestone decomposed.

We can use the molar mass of CaCO3 (100.09 g/mol) to convert 25.0 g to moles:

25.0 g CaCO3 × (1 mol CaCO3/100.09 g CaCO3) = 0.2497 mol CaCO3

Now we can use the proportionality of the heat change to calculate the heat change for the given quantity:

Heat change = (176 kJ/1 mol CaCO3) × (0.2497 mol CaCO3) = 44.0 kJ

Therefore, the best choice is C, which is the only option that matches this calculation.

The Thermochemical Equation Describing the Heat Change in the Decomposition