Question

${10}^{-4}$ g of gelatin is required to be added to 100 $c{m}^3$ of a stanadard gold solution to just prevent its precipitation by addition of 1 $c{m}^3$ of 10% NaCl solution to it. Hence, gold number of gelatin is?

• A. 10
• B. 1
• C. 0.1
• D. 0.01

Answer 1

The correct option is D 0.01

${10}^{-4}g=0.1mg$
$100c{m}^3$ of gold sol require 0.1 mg
$\therefore 10c{m}^3$ of gold sol will required 0.01 mg
Hence, gold number = 0.01.