When `1.0 xx 10^(-5) mg` of a protective colloid is added to 20 ml of standard gold sol, the precipitation of gold sol was prevented by adding 5 ml of 10% solution of NaCl. If the gold number of protective colloid is `2.0 x 10^(-x)` mg then x is = __?  

Answer

6

Explanation

`20 rarr 1 xx 10^(-5) mg , 10 ml rarr ? `
`(10^(-5) xx 10)/(20) = 0.5 xx 10^(-5) , 5 ml to 0.5 xx 10^(-5) , 1 rarr ? , 0.1 xx 10^(-5) = 1 xx 10^(-6)`.