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 190.0 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 23.87 °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 5.20 J/°C.

Request the qsoln qcal qrxn and Hrxn

Explanation / Answer

heat absorbed(q) = m*S*DT + c*DT

m = mass of solution = 60 grams

S = specificheat of solution = 4.06 j/g.c

DT = 25-23.87 = 1.13 c

c = heat capacity of calorimeter = 5.2 j/c

DT = 1.13 c

qabsorbed = 60*4.06*1.13 + 5.12*1.13    = 281.0536 joule.

No of moles of sample = 10/190 = 0.5263 mole

so that, 0.5263 mole sample gives = 281.0563 joule.

           1 mole sample    = 281.0563/0.5263 = 534.023 joule/mole

DHrxn = 534.023 joule/mole

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