Test #1 Question 6

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William Lan 2l
Posts: 73
Joined: Fri Sep 29, 2017 7:07 am

Test #1 Question 6

Postby William Lan 2l » Mon Feb 12, 2018 1:07 am

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?

Diane Bui 2J
Posts: 61
Joined: Sat Jul 22, 2017 3:00 am

Re: Test #1 Question 6

Postby Diane Bui 2J » Mon Feb 12, 2018 2:25 am

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).

Nha Dang 2I
Posts: 53
Joined: Fri Sep 29, 2017 7:07 am

Re: Test #1 Question 6

Postby Nha Dang 2I » Mon Feb 12, 2018 2:26 am

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.

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