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JEE Main levelOne or more correct optionsDifficulty 2 of 3ie025

For $0.01 M$ aqueous ammonia ( $K_{b} = 1.8 \times 1 0^{- 5}$ , 298 K), which statements are correct? (Use $α = K_{b} / c$ .)

ADegree of ionisation is about $4.2%$ .
B $[OH X^{-}] \approx 4.2 \times 1 0^{- 4} M$ .
CThe pH of the solution is about $3.37$ .
DAdding solid $NH X_{4} Cl$ decreases the degree of ionisation of ammonia.

Answer: A, B, D

α = 1.8 \times 1 0^{- 3} = 0.0424

(

4.2%

) and

[OH X^{-}] = c α = 4.2 \times 1 0^{- 4} M

. This gives

pOH = 3.37

and

pH = 10.63

, so option 3 is false. The common ion

NH X_{4} X^{+}

suppresses ionisation (option 4 true).

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