Question

A 90.2 mL sample of 1.00 M NaOH is mixed with 45.1 mL of 1.00 M H2SO4 in a large Styrofoam coffee cup; the cup is fitted with a lid through which passes a calibrated thermometer. The temperature of each solution before mixing is 21.45 °C. After adding the NaOH solution to the coffee cup and stirring the mixed solutions with the thermometer, the maximum temperature measured is 30.90 °C. Assume that the density of the mixed solutions is 1.00 g/mL, that the specific heat of the mixed solutions is 4.18 J/(g·°C), and that no heat is lost to the surroundings.

Write a balanced chemical equation for the reaction that takes place in the Styrofoam cup. Remember to include phases in the balanced chemical equation.

Calculate the enthalpy change per mole of H2SO4 in the reaction.

Answer 1

The balanced chemical equation for the reaction that takes place in the styrofoam cup is

Number of moles of

Temperature change

Total volume

Density is 1.00 g/mL

Mass of solution

The specific heat of mixed solution is

The enthalpy change

This is enthalpy change for 0.0451 moles of sulfuric acid.

For one mole of sulfuric acid, the enthalpy change is

Convert the unit from J to kJ

Hence, the enthalpy change per mole of sulfuric acid is 119 kJ/mol.