## need some help with questions (should be easy)

spirocycle - 15-4-2011 at 10:16

Calculate (delta)E when one mole of liquid is vaporized at its boiling point (80 C) and 1 atm pressure.
[enthalpy of vaporization = 30.7 kJ/mol]
the answer should be 27.8 kJ

I am kind of confused because if the enthalpy is 30.7 kJ/mol, shouldnt the change in energy be 30.7 kJ to vaporize one mol?

Consider the reaction: 2ICl + H2 -->2HCl + I2 (all gas).
At a certain temperature, the rate constant is found to be 1.62x 10^ -6 L/mol*s . What is the overall order of the reaction?
Ans: second

How can I figure this out without knowing how many steps and which is slow/fast, etc?

The bond angle in H2O is approximately 105 degrees while the bond angle in H2S is approximately 90. Why?
the answer is "O uses SP3 hybrid orbitals for bonding, while S uses 3P orbitals"

this answer seems screwy to me. why would the hybridization be different? I would expect it to have to do with the size of S and the difference in electronegativity.

spirocycle - 15-4-2011 at 10:38

I drew a mechanism for the reaction:

2ICl --- > Cl- + IICl (slow)
IICl + H2 -- > I2 + HCl + H+ (fast)
H+ + Cl- --> HCl (fast)

where IICl has a divalent iodine holding a positive charge

It fits the question, but seems a bit funky to me.