Question

Calculate the amount of heat released when 50 grams of NaOH is dissolved in 500 mL of water at 25°C. The heat of crystallization of NaOH is -44.51 kJ/mol. Assume the final temperature of the solution is 25°C and the heat capacity of the solution is 4.18 J/g °C.

Answer 1

To calculate the amount of heat released when 50 grams of NaOH is dissolved in 500 mL of water at 25C, we need to first determine the number of moles of NaOH and then use the heat of crystallization to find the total heat released.1. Calculate the number of moles of NaOH:The molar mass of NaOH is approximately 40 g/mol  23 g/mol for Na, 16 g/mol for O, and 1 g/mol for H .Number of moles = mass / molar massNumber of moles = 50 g / 40 g/mol = 1.25 mol2. Calculate the heat released from dissolving NaOH:Heat released = number of moles  heat of crystallizationHeat released = 1.25 mol   -44.51 kJ/mol Heat released = -55.64 kJSince the heat released is negative, it indicates that the process is exothermic, meaning heat is released to the surroundings. The total amount of heat released when 50 grams of NaOH is dissolved in 500 mL of water at 25C is 55.64 kJ.