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JEE Main 202229 JuneEvening Shift
Exam
JEE Main
Year
2022
Date
29 June
Shift
Evening Shift
Subject
Chemistry
Chapter
Surface Chemistry

JEE Main 2022 · 29 June · Evening Shift · Chemistry · Surface Chemistry

42 . 12 % (w/v) solution of NaCl causes precipitation of a certain...

42.1242 . 12 % (w/v) solution of NaClNaCl causes precipitation of a certain sol in 1010 hours. The coagulating value of NaClNaCl for the sol is
[Given : Molar mass : Na=23.0gmol−1;Cl=35.5gmol−1Na = 23 . 0g{mol}^{- 1}; Cl = 35 . 5g{mol}^{- 1}]

Options

  1. A36mmolL−136{mmolL}^{- 1}
  2. B36molL−136mol{L}^{- 1}
  3. C1440molL−11440mol{L}^{- 1}
  4. D1440mmolL−11440m{molL}^{- 1}

Correct answer

D. 1440mmolL−11440m{molL}^{- 1}

Step-by-step solution

The minimum concentration of an electrolyte in millimoles per litre required to cause precipitation of a sol in two hours is called coagulating value.

42.1242 . 12 % means100mlsolutioncontain42 . 12gofsalt . molesofsalt = \dfrac{42 . 12}{58 . 5} = 0 . 72moles = 720milimoles

Since 100 ml required 720 milimoles

therefor 1 L will required 7200 milimoles.

It will coagulate in 10 hours so for 2 hours = 5×7200=14400milimolL−15 \times 7200 = 14400milimol{L}^{- 1}

Note: NTA has either made mistake in question data or in options.

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