A coffee cup calorimeter was used to measure the heat of reaction - the change i

Question

A coffee cup calorimeter was used to measure the heat of reaction - the change in enthalpy that occurs when a solid dissolves in water. A 10.0 g sample of an ionic compound with a molar mass of 130.0 g/mol was added to a sample of deionized water to produce 60.0 grams of solution. After stirring and dissolving the solid, the temperature was found to change from 25.00 °C to 23.85 °C. Calculate the enthalpy of reaction Hrxn, per mole of salt dissolved. Assume the specific heat of the solution is 4.06 J/(g·°C) and the heat capacity of the calorimeter is 3.70 J/°C.

Calculate the heat change experienced by the calorimeter contents, qsoln.

Calculate the heat change experienced by the calorimeter, qcal.

Calculate the heat change produced by the reaction process, qrxn.

Calculate Hrxn, the enthalpy of reaction for one mole of solid in kJ/mol.

Explanation / Answer

No of mol of compound = 10/130 = 0.077 mol

q absorbed = 60*4.06*(25-23.85)+3.7*(25-23.85)

             = 284.4 j

             = 0.284 kj

DHrxn = 0.284/0.077 = 3.69 kj/mol

q sol = 60*4.06*(25-23.85) = 0.28 kj

q cal = 3.7*(25-23.85) = 0.00426 kj

q rxn = 0.284 kj

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