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Topic: Molar heat of solution?  (Read 8582 times)

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Offline rudiment274

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Molar heat of solution?
« on: October 23, 2014, 05:37:16 PM »
When 4.21 grams of potassium hydroxide are added to 250 mL of water in a coffee cup calorimeter, the temperature rises by 4.14°C. Assume that the density and specific heat of the dilute aqueous solution are the same as those of H2O and calculate the molar heat of solution of potassium hydroxide in kJ/mol. C= 4.184 J/g*K
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qrxn= -qsolution=-m x C x ΔT

So, the mass of the solution is the 4.21 grams of KOH plus the 250 mL of water.
So, that's 4.21 g + (250 mL x 1 g/mL)= 254.21 g

Then we calculate the heat of the reaction by multiplying the mass times the specific heat times the change in temperature.

qrxn= -254.21 g x 4.184 J/g*°C x 4.14°C = -4247.47 J

Then we convert joules to kJ

Then to find the molar heat of KOH, we take q and divide it by the moles of the solution.

Is my process correct?

Offline Borek

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Re: Molar heat of solution?
« Reply #1 on: October 23, 2014, 05:54:17 PM »
Logic looks OK.
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