How does ammonia behave as a Bronsted base: #"(i) "NH_3(g) + 7/2O_2(g) rarr 2NO_2(g) + 3H_2O# #"(ii) "2NH_3(g) rarr NH_4^+ +NH_2^(-) # #"(iii) "NH_3(g) + H_3CBr(g) rarr H_3CBr(g) + HBr(g)# #"(iv) "NH_3(aq) +H_2O(l) rarr NH_4^+ + HO^-#?

1 Answer
anor277
Dec 4, 2015

The acid base reaction (the last one!).

Explanation:

Ammonia is a Bronsted base:

#NH_3(aq) + H_2O(l) rightleftharpoons NH_4^+ + OH^-# #pK_b = 4.75#

I am not going to solve this equation using #pK_b#, but most of the ammonia is present as #NH_3#, the free base.

For AS/A2 level; ammonia is a very water like solvent. In pure ammonia another acid/base equilibrium operates, that is comparable to the #H_3O^+; OH^-# equilibrium in water.

#2NH_3(l) rightleftharpoons NH_2^(-) + NH_4^+#

THIS ONLY OPERATES IN LIQUID AMMONIA; IT DOES NOT OPERATE IN WATER. The amide ion, #NH_2^-#, does not exist in water.

Related questions
See all questions in Acids and Bases
Impact of this question
2227 views around the world
You can reuse this answer
Creative Commons License