Hess's Law - enthalpy change question

_Lizabeth_

So I know it all adds up +344 ----> +350.

But how is -3 the answer? Why is it overall divided by 3?

Thanks :smile:

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Reply 1

charco

Study Forum Helper

Original post by _Lizabeth_

So I know it all adds up +344 ----> +350.

But how is -3 the answer? Why is it overall divided by 3?

Thanks :smile:

The question can't be answered without the enthalpy of vaporisation of both bromine and iodine ...

Reply 2

_Lizabeth_

Original post by charco

The question can't be answered without the enthalpy of vaporisation of both bromine and iodine ...

This is the answer, I just want to know why it's /2

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Reply 3

charco

Study Forum Helper

Original post by _Lizabeth_

This is the answer, I just want to know why it's /2

The enthalpy of formation only requires 1/2 mole of each of the halogens....

Reply 4

Sniperdon227

Original post by _Lizabeth_

So I know it all adds up +344 ----> +350.

But how is -3 the answer? Why is it overall divided by 3?

Thanks :smile:

0.5 I2 + 0.5 Br2 --> 1 IBr
Formation infers 1 mole (enthalpy of formation)

Reply 5

mors13

i know its very late, but just in case anyone else who finds this needs help,
0.5 Br2 + 0.5 I2 → IBr
enthalpy change = 0.5(193) + 0.5 (151) - 175 = -3

(edited 4 years ago)

Reply 6

txxxx

Original post by mors13

i know its very late, but just in case anyone else who finds this needs help,
0.5 Br2 + 0.5 I2 → IBr
enthalpy change = 0.5(193) + 0.5 (151) - 175 = -3