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Test #1 Question 6

Posted: Mon Feb 12, 2018 1:07 am
by William Lan 2l
How do you approach this problem? We are given 3 C (graphite), yet it tells us that 4 moles of C (graphite) is reacted. So how do we do this problem?

Re: Test #1 Question 6

Posted: Mon Feb 12, 2018 2:25 am
by Diane Bui 2J
In this question, you would still perform Hess's Law as usual but the enthalpy of the reaction obtained is for the reaction as written. In this case, the enthalpy of reaction is for 3 moles of C (gr) reacted. To find the enthalpy change for 4 moles of C (gr), you would divide by 3 moles and then multiply by 4 moles of C(gr).

Re: Test #1 Question 6

Posted: Mon Feb 12, 2018 2:26 am
by Nha Dang 2I
I solved this by changing the reaction so that I would have 4 moles of C instead. I multiplied the entire reaction by 4/3 to get 4 C (graphite) + 16/3 H2 (g) --> 4/3 C3H8 (g). And then I did Hess's Law according to the new equation with the 4 moles of C.