[J-Mart]

I am given a solution of .1M Ammonium Nitrate and asked to calculate the pH. I do not know how to even really begin in dissociating it down into ions. Here's what I know:

NH4NO3(aq) --> N2O(g) + H2O(l)

H2O <==> H+ + OH-

I don't really know how to pull it all together or if I am even on the right track. 

[LQ43]

No, not quite on the right track.

NH4NO3 --> NH4+  +  NO3-

which one of these ions will affect pH?


then check this out
http://www.chembuddy.com/?left=pH-calculation&right=pH-salt-solution

[boesmanprinses]

Actually when AmoniumNitrate is heated up you will get N2O and 2H20
NH4NO3 ----> N20 +2H2O

If I am Wrong Please tell me?? and State youre reason

[Borek]

It decomposes - slowly. You will have plenty of time to measure pH

[AWK]

Actually when AmoniumNitrate is heated up you will get N2O and 2H20
NH4NO3 ----> N20 +2H2O

If I am Wrong Please tell me?? and State youre reason

This is out of subject (frankly saing, a very narrow temperature range is needed).
Use Ka of NH₄⁺

[chienbinhnam2324]

You were wrong ! When we heat the solution of ammonium Nitrate , there will be exist the equation that NH4NO3 --> N2O + H2O
In the water , NH4NO3 is dissolved into NH4+ and NO3-
There is a reversible equation :
NH4+ <=> NH3 + H+ Ka
and then we have a solution for this problem .

[AWK]

You were wrong ! When we heat the solution of ammonium Nitrate , there will be exist the equation that NH4NO3 --> N2O + H2O
In the water , NH4NO3 is dissolved into NH4+ and NO3-
There is a reversible equation :
NH4+ <=> NH3 + H+ Ka
and then we have a solution for this problem .

when we heat solution, nothing is happen. For thermal decomposition we need higher temperature

What des mean this eqution?

[Borek]

You were wrong !

Who "you"? 5 people posted earlier in this thread.

[Saint]

Well NO₃^- does not react with water (dissolve in water i mean, or ionize in water, Actually i am new one here and i am not adapted with english words of Chemistry) because the conjugative(συζυγες for those who are Greek) acid is strong

So
NH₄NO₃ ->NH₄⁺ + NO₃^-

goes to

NH₄^- + H₂O -> NH₃ + H₃O⁺

If we know Kb of NH₃ which is i think 10^-5
with Kw we have Ka=Kw/Kb
If it's 25^oC Kw=10^-14 so Ka=10^-9

Ka=[NH₃][H₃O⁺]/[Nh₄⁺]

then
[NH₃]=[H₃O⁺]=x
[Nh₄⁺]= C-x=1-x

so
10^-9=x²/1-x
Ka/C<0,01 so from the approximate calculation we have:
10^-9=x²
PH=5-1/2log10=4,5

Is that solution ok. I tried to be complete...
(By the way Hi Everyone!)

[Borek]

Well NO₃^- does not react with water (dissolve in water i mean, or ionize in water, Actually i am new one here and i am not adapted with english words of Chemistry) because the conjugative(συζυγες for those who are Greek) acid is strong

In general - you are right. For the nitpickers, nitric acid is the weakest of strong acids, with pKa=-1.

Your approach seems correct, just Kb of ammonia is 1.8x10^-5.

Please read forum rules (especially Answering Questions section).

[AWK]

Nh4+]= C-x=1-x

The concentration of ammonium nitrate is 0.1, not 1 M.
pH of 0.1 M NH4NO3 is about 4.1 (pH of 1 M - about 4.6)