Question

Calculate the enthalpy change (in kJ/mol) for dissolving 10 grams of NaOH in 100 mL of water at 25°C, given that the molar heat of solution for NaOH is -444.6 kJ/mol.

Answer 1

First, we need to determine the number of moles of NaOH in 10 grams. The molar mass of NaOH is:Na = 22.99 g/molO = 16.00 g/molH = 1.01 g/molMolar mass of NaOH = 22.99 + 16.00 + 1.01 = 40.00 g/molNow, we can calculate the number of moles of NaOH in 10 grams:moles of NaOH = mass / molar massmoles of NaOH = 10 g / 40.00 g/mol = 0.25 molNow that we have the number of moles, we can calculate the enthalpy change for dissolving 0.25 mol of NaOH using the given molar heat of solution:Enthalpy change = moles  molar heat of solutionEnthalpy change = 0.25 mol   -444.6 kJ/mol  = -111.15 kJThe enthalpy change for dissolving 10 grams of NaOH in 100 mL of water at 25C is -111.15 kJ.