To calculate the enthalpy change when 50 grams of potassium chloride KCl dissolve in 200 ml of water, we need to determine the number of moles of KCl and then use the molar enthalpy of dissolution.First, let's find the number of moles of KCl:Molar mass of KCl = 39.1 g/mol for K + 35.5 g/mol for Cl = 74.6 g/molNumber of moles = mass / molar massNumber of moles = 50 g / 74.6 g/mol = 0.670 molesNow, we can calculate the enthalpy change using the molar enthalpy of dissolution:Enthalpy change = number of moles molar enthalpy of dissolutionEnthalpy change = 0.670 moles -17.8 kJ/mol Enthalpy change = -11.93 kJThe enthalpy change when 50 grams of potassium chloride dissolve in 200 ml of water at a temperature of 25C is approximately -11.93 kJ.