A coffee cup calorimeter is prepared, containing 100.000 g of water (specific he

Question

A coffee cup calorimeter is prepared, containing 100.000 g of water (specific heat capacity = 4.184 J/g K) at initial temperature 80.000 C. A salt weighing 2.394 g is quickly added. The salt has a molar mass of 257.799 g/mol. The final temperature of the solution is 11.450 C.

Assume no heat loss to the surroundings. Assume the specific heat capacity of the solution is equal to that of pure water, and that the mass of the solution is equal to the mass of the solid plus the mass of water in the calorimeter.

What is the molar heat of solution for the salt, in kJ/mol?

Report your answer to three digits after the decimal.

Explanation / Answer

Solution:-

Total mass of solution = 100.000 g +2.394 g =102.394 g

Mass of solute =2.394 g

Specific heat of solution = 4.184 J/gC

Initial temperature =80.000C

Final temperature =11.450 C

Molar mass of solute =257.799 g/mol

Lets calculate the amount of heat absorbed by the dissolution of the salt

q= m*c*delta T

=102.394 g *4.184 J/gC* (80.000 C-11.450 C)

=29367.951 J

Converting joules to kJ

[29367.951 J*1kJ] /1000J = 29.368 kJ

Now using the mass of solute and molar mass we can find the molar heat of solution

[29.368 kJ * 257.799 g per mol] / 2.394 g = 3162.507kJ/mol

Hence the molar heat of solution is 3162.507 kJ/mol

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