Question

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]

विकल्प

• 36 mmol L^-1

• 36 mol L^-1

• 1440 mol L^-1

• 1440 mmol L^-1

Answer 1

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 1440 mmol L^-1. 

Explanation:

Given: 42.12 g NaCl in 100 mL

Molar mass of Na = 23.0 g mol^-1

Molar mass of Cl = 35.5 g mol^-1

Molarity (M) = `"n"/"V"`

M = `(42.12 xx 1000)/((23 + 35.5) xx 100)`

M = `(42.12 xx 10)/58.5`

= 7.2

Coagulation value = Number of milli mole of electron/Volume of solution

Number of milli mole of electron = 7200

Coagulation value for 10 hours = 7200

Coagulation value for 2 hours

= `7200/10 xx 2`

= 1440 m mol L^-1