[Ben Cohen]

Hi, I have two questions:

I saw a question that said "The expected bond angle for NH3 is 109.5, but it has been experimentally determined to be 107.5 degrees."
I know the reason behind the smaller angle, but how exactly do you "experimentally determine" a bond angle?

Also, the question wanted me to write the products (don't have to balance): "Nitrogen dioxide gas is bubbled into water."
I got:
H2O + NO2 --> H+ + HNO3 or I was thinking possibly H2O + NO2 --> H2 + HNO3 (remember I don't have to balance).
This was not the correct answer, however. The answer is:
H2O + NO2 --> H+ + NO3 - + NO
this doesn't make any sense to me - why would it make NO3- and NO? Is this one of those "you have to know it" or is there actually a way to reason this out? Usually a ___dioxide gas bubbled into water makes an acid, like H2O + CO2 --> H2CO3 or SO2 + H2O --> H2SO3. What is the explanation for this?

[AWK]

_{I know the reason behind the smaller angle, but how exactly do you "experimentally determine" a bond angle?}
eg: microwave spectroscopy (http://www.cem.msu.edu/~cem472/micro.pdf), X-ray, neutron and electron diffractions

_{H2O + NO2 --> H+ + NO3 - + NO}
This is the method of large scale industrial production of HNO3 (Ostwald process)
http://en.wikipedia.org/wiki/Ostwald_process

[Ben Cohen]

So this is one of those things you would just have to memorize?

[Olympiad_Tutor]

Hi, I have two questions:
...
H2O + NO2 -->.

check the oxidation states of N.

compare this to oxidation state of Carbon in H2O + CO2-->.