A mixture of KBr and NaBr weighing 0.560 gm was treated with aqueous Ag+ and all the bromide ion was recovered as 0.970 gm of pure AgBr. The fraction by weight of KBr in the sample is

Q: A mixture of KBr and NaBr weighing 0.560 gm was treated with aqueous Ag+ and all the bromide ion was recovered as 0.970 gm of pure AgBr. The fraction by weight of KBr in the sample is

(A) 0.25 gm

(B) 0.2378

(C) 0.36

(D) 0.285

Sol:  KBr + NaBr          +  Ag+  →AgBr

a gm    (0.56 – a)                    0.97 gm

Applying POAc for Br atom 1 × nKBr  + 1 × nNaBr = 1 × nAgBr

$\large \frac{a}{119} + \frac{0.560 a}{103} = \frac{0.97}{188} $

∴  a = 0.1332 gm

∴ Fraction of KBr in the sample = 0.1332/0.560 = 0.2378

Ans: (B)