Same quantity of electricity was passed through solutions of salts of elements A,B and C with atomic weights 7, 27 and 48 respectively. The masses of A,B and C deposited were 2.1 g,27.7g and 7.2 respectively. The valencies of A,B and C respectively are

Same quantity of electricity was passed through solutions of salts of

1.	Same quantity of electricity was passed through solutions of salts of elements A,B and C with atomic weights 7, 27 and 48 respectively. The masses of A,B and C deposited were 2.1 g,27.7g and 7.2 respectively. The valencies of A,B and C respectively are
Answer» 3,2 and 1 1,2 and 3 1,3 and 2 2,3 and 2 Solution :Suppose valencies of A,B and C are a,b, and c respectively. Then their EQUIVALENT weights will be (At. Wt/valance) 7/a,27/b and 48/c. when same quantity of electricity is passed, masses DEPOSITED are in the ratio of their equivalent weights, i.e., `("Mass of A")/("Eq. wt. of A")=("Mass of B")/("Eq. wt of B")=("Mass of C")/("Eq. wt of C")` `therefore(2.1)/(7//a)=(2.7)/(27//b)=(7.2)/(48//c)` or 0.3 a=0.1, b=0.15c, or 3a=b=1.5c. thus, if b=1, then `a=(1)/(3)`, `c=(1)/(1.5)=(2)/(3)` `therefore`Ratio `a:b:c=(1)/(3):1:(2)/(3)=1:3:2`