Question

The fluorocarbon compound C2Cl3F3 has a normal boiling point of 47.6 ∘C. The specific heats of C2Cl3F3(l) and C2Cl3F3(g) are 0.91 J/g⋅K and 0.67 J/g⋅K, respectively. The heat of vaporization for the compound is 27.49 kJ/mol. Calculate the heat required to convert 47.5g of C2Cl3F3 from a liquid at 10.60∘C to a gas at 81.80∘C.

a. First, I used Q=mCdeltaH for liquid C2Cl3F3
47.5g x .91 J/g-K x (47.6-10.6) = 1599.3

b. Than, I used the same equation to find the heat for it to vaporize.
(47.5g/187.5 g/mol) x 27.49 kJ/mol x 1000J = 6964.1

c. Last, I had to find what the energy would be to warm it to 81 from its boiling point.
47.5g x .67J/g-k x (81.8-47.6) = 1088.4

Adding a+b+c to get the total energy, I got 9651.82, or with 2 sigfigs, 9700 kJ.

I am not sure what I am doing wrong, but 9700 is not the right answer, would love any help I can get!

Answer 1

Thanks for showing your work. Your work looks ok and the substitutions look ok.
I think the trouble may be the number of s.f.. If I round a to 1.6E3 (2 s.f.) and add to b rounded to 3 s.f. of 6.96E3 and add to c rounded to 2 s.f. of 1.1E3, I get 9.66E3 which rounded gives 9.7E3 to 2 s.f. Try changing your answer to 9.7E3.
The only other thing I noted was I obtained 187.325 for the molar mass of the compound I didn't go through and see if that will make a different of one digit in the answer or not. My quick guess is that it will not. It is enough to make that b phase 9.97E3 instead of 6.96 but that isn't enough to change the final number.

Answer 2

Your calculations are precise; however, your final calculation is 9700 J. You are answering as kJ. You must convert to 9.70 kJ.

Answer 3

10 kj