## quiz 1 #4, finding standard rxn enthalpy

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

Ivanna_Tang_3B
Posts: 22
Joined: Wed Sep 21, 2016 2:58 pm

### quiz 1 #4, finding standard rxn enthalpy

Quiz 1 #4
The question gives that, the formation of of lactic acid from glucose is C6H12O6-->2C3H6O3 and asks you to calculate the standard enthalpy change. I ended up with -113.8kJ and then divided by 2 to get -56.9kJ/mol. But this part was marked wrong, and apparently -113.8kJ is correct. Why am I not supposed to divide by 2 to get the amount per mole?

Thank you!

Chem_Mod
Posts: 18400
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 435 times

### Re: quiz 1 #4, finding standard rxn enthalpy

Standard reaction enthaply means the enthalpy of the given reaction at standard conditions. Standard conditions have not relationship with stoichiometry number of the reaction. Therefore you should stick to the target reaction given. Dividing it by 2 is unnecessary.