To calculate the heat evolved when NaOH is dissolved in water, we need to determine the number of moles of NaOH and then use the enthalpy of solution to find the heat evolved.First, let's find the number of moles of NaOH:NaOH has a molar mass of 22.99 g/mol Na + 15.999 g/mol O + 1.007 g/mol H = 39.996 g/mol.Now, we can find the number of moles:moles of NaOH = mass / molar massmoles of NaOH = 25 g / 39.996 g/mol = 0.625 molNow, we can use the enthalpy of solution to find the heat evolved:Heat evolved = moles of NaOH enthalpy of solutionHeat evolved = 0.625 mol -44.5 kJ/mol = -27.8125 kJSince the enthalpy of solution is negative, the heat is evolved exothermic reaction , and the heat evolved is 27.8125 kJ.