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Question Paper from: IIT JEE Main 2021 TestSeries Paper 2

The gold number of starch is 25. How much of it is required to prevent coagulation of 100ml of gold soln adding 1ml of 10% NaCl solution?

25mg

250mg

2.5mg

0.250mg

Solution:

Chapter Name: Surface Chemistry

Difficulty Level: Moderate

The gold number is defined as the number of milligrams of the protective colloids required to just prevent the coagulation of 10 ml of standard gold sol when 1ml of 10% solution of NaCl is added to it is called gold number.

The gold number of starch is 25. This means 25mg starch is required to be added to 10 ml of gold sol to completely prevent coagulation of 1ml of 10% NaCl. Therefore. starch added to 100ml of gold soln.

$\frac{25 \times 100}{10} = 250 m g$

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IIT JEE Main 2021 TestSeries Paper 2

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