Question

Calculate the standard enthalpy change (in kJ/mol) for the dissolution of 3.50 g of potassium hydroxide (KOH) in 250.0 mL of water at 25°C, given that the molar heat of solution of KOH is -57.61 kJ/mol.

Answer 1

To calculate the standard enthalpy change for the dissolution of potassium hydroxide, we first need to determine the number of moles of KOH dissolved and then use the molar heat of solution to find the enthalpy change.1. Calculate the number of moles of KOH:KOH has a molar mass of 39.10 g/mol  K  + 15.999 g/mol  O  + 1.008 g/mol  H  = 56.108 g/mol.moles of KOH = mass / molar massmoles of KOH = 3.50 g / 56.108 g/mol = 0.0624 mol2. Calculate the standard enthalpy change:Standard enthalpy change = moles of KOH  molar heat of solutionStandard enthalpy change = 0.0624 mol  -57.61 kJ/mol = -3.60 kJThe standard enthalpy change for the dissolution of 3.50 g of potassium hydroxide in 250.0 mL of water at 25C is -3.60 kJ.