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 0.83 g of KOH(s) are dissolved in 115.10 g of water, the temperature of the solution increases from 23.76 to 25.57 °C. The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.75 J/°C. Based on the student's observation, calculate the enthalpy of dissolution of KOH(s) in kJ/mol. Assume the specific heat of the solution is equal to the specific heat of water. Hdissolution =____________ kJ/mol

Explanation / Answer

m = 0.83 g of KOH

m = 115.10 g W

dT = 25.57-23.76 = 1.81°C

C = 1.75 J/C

dHRxn = ? kJ/mol

Cp = 4.18 J

Q = m*Cp*dT

Q = (0.83+115.10)*4.184*(1.81) = -877.942527 J

mol = mass/MW =0.83/ 56.1 = 0.01479 mol of KOH

E = Q/n = 877.942/0.01479 =59360.513 J/mol or = -59.360 kJ/mol

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

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