Question

M1X and M2X are the salts of a weak base and strong acid. Kh values for them are 10–7 and 10–4 respectively. Kb for M3OH is 10–4 . The decreasing order of base strength would be :
(1) M2OH, M1OH, M3OH
(2) M1OH, M3OH, M2OH
(3) M3OH, M1OH, M2OH
(4) M1OH, M2OH, M3OH

Answer 1

Answer on Question #42598, Chemistry, Other

Question:

M1X and M2X are the salts of a weak base and strong acid. Kh values for them are 10–7 and 10–4 respectively. Kb for M3OH is 10–4. The decreasing order of base strength would be :

(1) M2OH, M1OH, M3OH

(2) M1OH, M3OH, M2OH

(3) M3OH, M1OH, M2OH

(4) M1OH, M2OH, M3OH

Solution:

Hydrolysis constant of salt obtained from Strong acid and Weak base is:

$$\mathrm{Kh} = \mathrm{Kw} / \mathrm{Kb}$$

Therefore:

$$Kb = Kw / Kh$$ $$Kb(M1OH) = \frac{10^{-14}}{10^{-7}} = 10^{-7}$$ $$Kb(M2OH) = \frac{10^{-14}}{10^{-4}} = 10^{-10}$$

And the decreasing order of base strength (Kb) would be $10^{-4} > 10^{-7} > 10^{-10}$

Answer: (3) M3OH, M1OH, M2OH.

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