When a solid dissolves in water, heat may be evolved or absorbed. The heat of di

Question

When a solid dissolves in water, heat may be evolved or absorbed. The heat of dissolution (dissolving) can be determined using a coffee cup calorimeter. In the laboratory a general chemistry student finds that when 6.89 g of K2SO4(s) are dissolved in 100.80 g of water, the temperature of the solution drops from 23.33 to 20.88 °C. The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.65 J/°C. Based on the student's observation, calculate the enthalpy of dissolution of K2SO4(s) in kJ/mol. Assume the specific heat of the solution is equal to the specific heat of water.

H dissolution = ---------- kJ/mol

Explanation / Answer

(4.18 J/g·°C) x (100.80 g) x (23.33 - 20.88)°C = 1032.29 J lost by the water

Supposing the calorimeter to be at the same temperatures as the water:
(1.65J/°C) x (23.33 - 20.88)°C = 4.04J lost by the calorimeter

1032.29 J + 4.04 J = 1036.33 J total lost by the combined apparatus, and gained by the solute

(1.03633 kJ) / 0.039 =26.57 kJ/mol {no.of mole of k2so4 = 6.89/174.259 = 0.039}

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.