Question

Calculate the standard enthalpy change for the dissolution of 10 grams of NaCl in water at 25°C, given that the molar enthalpy of dissolution of NaCl is -3.9 kJ/mol.

Answer 1

To calculate the standard enthalpy change for the dissolution of 10 grams of NaCl, we first need to determine the number of moles of NaCl in 10 grams.The molar mass of NaCl is approximately 58.44 g/mol  22.99 g/mol for Na and 35.45 g/mol for Cl .Number of moles = mass / molar massNumber of moles = 10 g / 58.44 g/mol  0.171 molNow, we can use the molar enthalpy of dissolution to calculate the standard enthalpy change.Standard enthalpy change = number of moles  molar enthalpy of dissolutionStandard enthalpy change = 0.171 mol   -3.9 kJ/mol   -0.667 kJThe standard enthalpy change for the dissolution of 10 grams of NaCl in water at 25C is approximately -0.667 kJ.