## 6th edition 8.61

Jeremiah Hutauruk
Posts: 67
Joined: Fri Sep 28, 2018 12:28 am

### 6th edition 8.61

8.61 Calculate the reaction enthalpy for the synthesis of hydrogen bromide gas, H2(g) Br2(l) S 2 HBr(g), from the following data:
NH 1g2 HBr1g2 ¡ NH Br1s2 34
¢H° 188.32 kJ N 1g2 3 H 1g2 ¡ 2 NH 1g2 ¢H° 92.22 kJ
223
N 1g2 4 H 1g2 Br 1l2 ¡ 2 NH Br1s2
2 2 2 4
¢H° 541.66 kJ

Manya Bali 4E
Posts: 66
Joined: Fri Sep 28, 2018 12:23 am

### Re: 6th edition 8.61

So you have to manipulate the reactions given, either by reversing them (in which case, the delta H of the reaction changes sign), or by multiplying them by a constant (in which case, delta H is also multiplied by the constant), such that when the reactions are added together, you get the final reaction you wanted to find delta H for to start with. I attached a picture and tried to color code the changes I made. Hopefully this helps!

AnnaYan_1l
Posts: 96
Joined: Fri Apr 06, 2018 11:05 am
Been upvoted: 1 time

### Re: 6th edition 8.61

The explanation above is really great! Just a quick correction, delta H = 2(188.32) - 541.66 + 92.22 = -72.90 not 72.90

:)

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