To calculate the enthalpy change, we first need to determine the number of moles of KCl being dissolved. The molar mass of KCl is 39.1 g/mol for potassium + 35.45 g/mol for chlorine = 74.55 g/mol.Now, we can find the number of moles of KCl in the 10 g sample:moles of KCl = mass / molar massmoles of KCl = 10 g / 74.55 g/molmoles of KCl 0.134 molNow that we have the number of moles, we can calculate the enthalpy change using the molar enthalpy of solution:enthalpy change = moles molar enthalpy of solutionenthalpy change = 0.134 mol -17.6 kJ/mol enthalpy change -2.36 kJSo, the enthalpy change when 10 g of potassium chloride is dissolved in 100 mL of water at 25C is approximately -2.36 kJ.