Chem Destroyer #19 Question

[20090900]

---

Members do not see this ad.

This question is from the CHEM section of 2012-DAT destroyer

19) Which of the following does not have a standard enthalpy of formation of zero at 1atm and 24 degrees Celsius?

a) Cl2 (g)
b) I2 (s)
c) H2 (g)
d) Br2 (g)
e) H2O (l)

* I understand why the answer is E but isn't B also technically wrong as well. I guess you could argue that E is the most correct answer but I would just like some conformation on this. I'm pretty sure Iodine exists naturally as a diatomic gas. Therefore I2 (s) should not have a standard enthalpy of formation of 0 right?

Thanks!

 

[NDPitch]

I think it's because it doesn't matter what phase it's in to be considered "elemental form". For example, whether you have gaseous nitrogen, or liquid nitrogen, both are still N2, which is elemental form!

 

[lutopie0730]

I2 is solid at 24 degree celcius. So B does not have any problem. However, the answer is D and E. Br2 is liquid at the room temperature, which means standard enthalpy of formation of gaseous Br2 cannot be zero. Maybe a small mistake ;-)

 

[20090900]

Whoops my bad.

D should be Br2 (liquid) not (gas). OK thanks, did not know I2 is a solid at 24C.