TopScore Test 1 G.Chem Question 50 or 10.

[ILikeTeeth]

Advertisement - Members don't see this ad

Hello All,

Hope someone can help me. The reason I wrote question 50 or 10, is b/c it depends how you look at it. If you are looking at all the 3 science section then its 50, if you are looking at just the G.Chem section then its 10. At least I think it works like that.

Here is the questions:

Given that the standard enthaply of fomation for NO(g) is 90.25 kJ/Mole, calculate the free energy change for the following reaction at 25 degree C.

N2(g) + O2(g) <----> 2NO(g)

Absolute Entropies are in J/Mole*K
N2(g) = 192
NO(g) = 211
O2(g) = 205

I hope to receive a clear explaination. I hate G.Chem. Thank you

 

[Rezdawg]

Weiy01 answered this in another thread...here is his answer:

--------------------------------------------------------------------
To determine free energy, use delta G=(delta H)-(T)(delta S).

Given that delta H=90.25kJ/mole, multiply by 2 since there are 2 moles in the equation. so 180.5kJ/mole.

In this case, T must always be in units of Kelvin, so K=273+25 celcius=298K

Solving for delta S= products - reactant= ((2)(211))-(205+192)= 25 J/molK. (This 25 J/molK has nothing to do with the given temperature 25 Celsius. ) Then, you convert 25 J/molK to kj/molK by multiplying by 10^-3 to keep units consistent.

Plug in your values you get ...

delta G = (180.5 kJ/mole) - (298 K)(25 J/molK)(10^-3 kj/J)

and whoalah! hope this helps