Question

Calculate the standard enthalpy change for the dissolution reaction of 10.0 g of NaOH(s) in 100.0 g of water at 25°C, given that the heat absorbed by the solution is 9.14 kJ. (Molar mass of NaOH = 40.00 g/mol and specific heat capacity of water = 4.18 J/g·°C)

Answer 1

To calculate the standard enthalpy change for the dissolution reaction of NaOH, we first need to determine the number of moles of NaOH and then use the heat absorbed by the solution to find the enthalpy change per mole of NaOH.1. Calculate the number of moles of NaOH:moles of NaOH = mass of NaOH / molar mass of NaOHmoles of NaOH = 10.0 g / 40.00 g/mol = 0.25 mol2. Convert the heat absorbed by the solution from kJ to J:9.14 kJ = 9.14 * 1000 J = 9140 J3. Calculate the standard enthalpy change per mole of NaOH:H = heat absorbed by the solution / moles of NaOHH = 9140 J / 0.25 mol = 36560 J/mol4. Convert the enthalpy change from J/mol to kJ/mol:H = 36560 J/mol *  1 kJ / 1000 J  = 36.56 kJ/molThe standard enthalpy change for the dissolution reaction of NaOH is 36.56 kJ/mol.