Question

Calculate the heat released when 10.0 g of solid NaOH at 25.0°C is dissolved in 200.0 mL of water also at 25.0°C, given that the heat of crystallization of NaOH is 44.5 kJ/mol and the density of water is 1.00 g/mL.

Answer 1

To calculate the heat released when 10.0 g of solid NaOH is dissolved in 200.0 mL of water, we will first determine the number of moles of NaOH and then use the heat of crystallization to find the heat released.1. Calculate the number of moles of NaOH:The molar mass of NaOH is 22.99 g/mol  Na  + 15.999 g/mol  O  + 1.007 g/mol  H  = 39.996 g/mol.Number of moles = mass / molar massNumber of moles = 10.0 g / 39.996 g/mol = 0.250 mol2. Calculate the heat released using the heat of crystallization:Heat released = number of moles  heat of crystallizationHeat released = 0.250 mol  44.5 kJ/mol = 11.125 kJTherefore, the heat released when 10.0 g of solid NaOH is dissolved in 200.0 mL of water is 11.125 kJ.