Question

Calculate the standard enthalpy change (∆H°) for the dissolution of 5 grams of table salt (NaCl) in water at 298 kelvin. The molar mass of NaCl is 58.44 g/mol and the heat capacity of the solution is 4.18 J/gK.

Answer 1

To calculate the standard enthalpy change  H  for the dissolution of NaCl in water, we need to know the standard enthalpy of solution for NaCl. The standard enthalpy of solution is the amount of heat absorbed or released when one mole of solute dissolves in a solvent to form a solution under standard conditions  298 K and 1 atm pressure . The standard enthalpy of solution for NaCl is -3.88 kJ/mol.First, we need to find the number of moles of NaCl in 5 grams:moles = mass / molar massmoles = 5 g / 58.44 g/molmoles = 0.0856 molNow, we can calculate the enthalpy change for the dissolution of 5 grams of NaCl:H = moles  standard enthalpy of solutionH = 0.0856 mol   -3.88 kJ/mol H = -0.332 kJThe standard enthalpy change for the dissolution of 5 grams of NaCl in water at 298 K is -0.332 kJ.