A common laboratory reaction is the neutralization of an acid with a base. When 50.0 mL of 0.500 M HCl at 25.0°C is added to 50.0 mL of 0.500 M NaOH at 25.0°C in a coffee cup calorimeter, the temperature of the mixture rises to 28.2°C. What is the heat of reaction per mole of acid? Assume the mixture has a specific heat capacity of 4.18 J/(g·K) and that the densities of the reactant solutions are both 1.00 g/mL.

Question

Quizplus · Accepted Answer

The heat absorbed by the solution can be calculated using q = mcΔT. The total mass of the solution is 100 g (since 50 mL + 50 mL and density is 1 g/mL). The temperature change ΔT is 3.2°C. Thus, q = 100 g * 4.18 J/(g·K) * 3.2 K = 1337.6 J. Since the reaction involves 0.025 moles of HCl (50 mL * 0.500 M), the heat of reaction per mole is 1337.6 J / 0.025 mol = 53,504 J/mol or approximately 54 kJ/mol.

A Common Laboratory Reaction Is the Neutralization of an Acid