Rush! How do I compute for heat of solution in kJ/mol given the mass, molar mass, moles, volume of water, initial temper

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Rush! How do I compute for heat of solution in kJ/mol given the
mass, molar mass, moles, volume of water, initial temperature of
water and final temperature of solution? Example: APPLICATION OF
THE CONCEPTS IN CALORIMETRY MgSO4 Mass of salt: 15 g MM of salt:
120 g/mol Moles of salt: 0.125 mol Volume of water: 30 mL Initial
temp. of water: 28°C Final temp. of solution: 72.8°C Heat of
solution in kJ/mol: ? Please provide the step by step solution and
explanation why was the problem solved that way especially on the
mass used in q= mc(tf-ti). What is the reason why that X grams is
used? Thank you !