Acid-Base solutions and their effectiveness for deprotonation of NH4+

[ada0713]

Consider the following solutions and their respective pH values. Which substance would be effective(K>1) for the deprotonation of NH4+ ?
0.1 M A, pH = 6.85
0.1 M B, pH = 7.22
0.1 M C, pH = 8.34
0.1 M D, pH = 11.88

1) A
2) B
3) C
4) D
5) none are effective

If the reaction to be effective
doesn't Strong acid have to react with strong base?
since NH4+ is strong acid, I thought it should react with the strongest
base among the four substances,
so i chose D, which has the highest pH value.

Is it right, or am I doing something wrong here?

 

[ada0713]

oh.. NH4+ is not a strong acid..
how do I approach this problem then?

If K>1, net direction is right,
then shouldn't the reactants be stonger acid and stronger base?

 

[ada0713]

anyone?

 

[symbolipoint]

Dissociation of ammonium as an acid is weak; I would guess the choice D is the strongest base allowed for you and that would be most effective in deprotonating the ammonium ion. I say it is the strongest base there because all of your choices are 0.1 Molar; and D has the highest pH (therefore most alkaline).

 

[Kushal]

i thought NH4+ would be a strong acid. NH3 is a weak base, it's conjugate acid, NH4+ should then be strong.

but you still need the strongest base... therefore D

 

[chemisttree]

Consider the following solutions and their respective pH values. Which substance would be effective(K>1) for the deprotonation of NH4+ ?
0.1 M A, pH = 6.85
0.1 M B, pH = 7.22
0.1 M C, pH = 8.34
0.1 M D, pH = 11.88

1) A
2) B
3) C
4) D
5) none are effective

If the reaction to be effective
doesn't Strong acid have to react with strong base?
since NH4+ is strong acid, I thought it should react with the strongest
base among the four substances,
so i chose D, which has the highest pH value.

Is it right, or am I doing something wrong here?

Why do you think you were given the pH at a particular concentration? Have you studied the concept of pKa? What 'K' was referred to in the question "...(K>1)..."?