Question

Calculate the Electron Affinity of F(g) in kJ/mole using Hess' Law?

Answer 1

The given information is:

Answer 2

IE1 + IE2 of Sr(g) is 1580 kj
Hsub of Sr(s) is 144 kJ
Hdiss of F2 is 79 kJ
Hf of SrF2 (s) is -1215 kJ
Hlatt of SrF2 (s) is -2441 kJ

Answer 3

i made the equations:
1. Sr(g)+Sr+(g) -> Sr2+(g) + Sr+(g) + 2e-
2. Sr (s) -> Sr(g)
3. F2(g) -> 2F(g)
4. Sr(s) + F2(g) -> SrF2
5. Sr2+(g) + F-(g) -> SrF2 (s)
from the given values

Answer 4

When I tried to:
flip 5
1/2 * flip 3
flip 1
flip 2
copy 4

I ended up with an extra 1/2 F2 that I couldn't cancel out. I'm not sure what to do.

Answer 5

@aaronq

Answer 6

I think it's because equation 5 is not balanced, it should be:

\(5. ~~Sr^{2+}(g) + \color{red}2F^-(g) -> SrF_2 (s)\)

which should cancel that \(\frac{1}{2}F_2\)

Answer 7

That was it, thank you.