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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3sc215

The flocculation values (mmol/L) of $KCl$ , $MgCl X_{2}$ and $AlCl X_{3}$ for a sol are 90, 1.2 and 0.10. Select the correct statement(s).

AThe sol is negatively charged.
BThe coagulating power of $MgCl X_{2}$ is 75 times that of $KCl$ (power taken as the reciprocal of the flocculation value).
CAt the flocculation point of $AlCl X_{3}$ the concentration of $Cl X^{-}$ is 0.10 mmol/L.
DThe flocculation values of $KCl$ , $MgCl X_{2}$ and $AlCl X_{3}$ are in the ratio 900 : 12 : 1.

Answer: A, B, D

The flocculation value falls with cation charge, so cations coagulate and the sol is negative.

90/1.2 = 75

gives statement 2. At the flocculation point of

AlCl X_{3}

,

[Cl X^{-}] = 3 \times 0.10 = 0.30

mmol/L, so statement 3 is wrong.

90/0.10 : 1.2/0.10 : 1 = 900 : 12 : 1

makes statement 4 correct.

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