Question

Determine the standard enthalpy change for the dissolution of 5.00 grams of magnesium chloride in water, given that the molar mass of MgCl2 is 95.21 g/mol and the standard enthalpy change of formation for magnesium chloride is -641.3 kJ/mol.

Answer 1

To determine the standard enthalpy change for the dissolution of 5.00 grams of magnesium chloride in water, we first need to calculate the number of moles of MgCl2 in 5.00 grams.Moles of MgCl2 = mass / molar massMoles of MgCl2 = 5.00 g / 95.21 g/molMoles of MgCl2 = 0.0525 molNow, we can use the standard enthalpy change of formation for magnesium chloride to find the enthalpy change for the dissolution of 5.00 grams of MgCl2.Standard enthalpy change for dissolution = moles of MgCl2  standard enthalpy change of formationStandard enthalpy change for dissolution = 0.0525 mol   -641.3 kJ/mol Standard enthalpy change for dissolution = -33.67 kJTherefore, the standard enthalpy change for the dissolution of 5.00 grams of magnesium chloride in water is -33.67 kJ.