Question

You are given the following data:

H₂(g) --> 2H(g) Delta H degrees=436.4 kJ/mol

Br₂(g) --> 2Br(g) Delta H degrees=192.5 kJ/mol

H₂(g) + Br₂(g) --> 2HBr(g) Delta H degrees=-72.4 kJ/mol

Calculate Delta H degrees for the reaction

H(g) + Br(g) --> HBr(g)

Answer 1

Hi, to calculate the for this reaction. We can do the following:

Add the first two equations to get atomic hydrogen and atomic bromine together. We are adding these two equations since we need both of these together in the fourth equation. We have the following equation after adding them.

We can now subtract this equation from our third equation to remove H2(g) and Br2(g)

Now, we have to divide this equation by 2 to get our desired equation. The resultant is:

     

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