JEE Main 2022 · 29 Jun · Shift 2 · Chemistry Q65

ChemistrySingle correct+4 / -1Question 65 of 90

A 42.12% (w/v) solution of NaCl causes precipitation of a certain sol in 10 hours. The coagulating value of NaCl for the sol is

[Given: Molar mass : Na = 23.0 g mol $^{-1}$ ; Cl = 35.5 g mol $^{-1}$ ]

36 mmol L

^{-1}

36 mol L

^{-1}

1440 mol L

^{-1}

1440 mmol L

^{-1}

Answer and worked solution

Official answer: D

Concentration. $\frac{421.2}{58.5}=7.2$ mol L $^{-1}$ coagulates the sol in 10 hours.

Coagulating value is defined for 2 hours; scaling inversely with time gives $\frac{7200}5=1440$ mmol L $^{-1}$ , the keyed option.

(D)

Topics:Colloids

JEE Main 2022 · 29 Jun · Shift 2, Chemistry question 65