C (gr) ?

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Christine Chen 1H
Posts: 64
Joined: Fri Sep 28, 2018 12:18 am

C (gr) ?

Postby Christine Chen 1H » Wed Feb 06, 2019 8:39 am

In problem 8.67 (Edition 6), the solutions guide has C (gr). What is (gr) and what is the significance of such?

Ashley Bouma 1F
Posts: 30
Joined: Fri Sep 28, 2018 12:21 am

Re: C (gr) ?

Postby Ashley Bouma 1F » Wed Feb 06, 2019 9:05 am

I believe that the book said that C(gr) was an abbreviation for graphite

Kate_Santoso_4F
Posts: 72
Joined: Fri Sep 28, 2018 12:29 am

Re: C (gr) ?

Postby Kate_Santoso_4F » Wed Feb 06, 2019 9:19 am

C(gr) represents carbon as graphite. Graphite is the most stable form of carbon at normal temperatures. The standard enthalpy of formation of an element in its most stable form is zero. For instance, the standard enthalpy of formation of C(gr) is zero because C(gr) --> C(gr) is a "null formation". However, the enthalpy of formation of an element in a form other than its most stable one is nonzero. For example, C(gr) --> C(diamond) is endothermic. The standard enthalpy of formation of diamond is +1.9 kj/mol.


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