What is the relation between Molar enthalpy and Change in enthalpy? How do we use them together?

Question

If I calculate Q=mc(delta t) as Q= (54.25 g)(4.19 J/g C)( 6 C) and get 1363.845 J. How do I convert this into change in enthalpy and molar enthalpy? This was done for a Calorimetry assignment.

Information

CaCl2 mass = 5.50 g

Water mass initial = 50.00 g

Solution mass final (water) = 54.25 g

Molar Mass CaCl2 = 110.98 g/mol

Initial temperature = 25.0 C

Final temperature = 31.0 C

Answer 1

What you have calculated is the change in enthalpy (q = ∆H at constant pressure), so now all you need to do to find the molar enthalpy is to find the moles of CaCl₂ used and divide the ∆H by that value. Thus,

5.50 g CaCl₂ x 1 mol CaCl₂/110.98 g = 0.0496 moles

Molar enthalpy = 1364 J/0.0496 mol = 27,500 J/mol = 27.5 kJ/mol