Question

2. To prepare standard 1 M solution of F.A.S.
a. 0.392 g of F.A.S. of dissolved in distilled water and diluted to 1 L of solution
b. 3.92 g of F.A.S. is dissolved in distilled water and diluted to 1 L of solution
c. 39.2 g of F.A.S. is dissolved in distilled water and diluted to 1 L of a solution
d. 392 g of F.A.S. is dissolved in distilled water and diluted to 1 L of solution​

Answer 1

50 ml of 0.1N potassium permanganate corresponds to 100050×0.1​=0.005eq.KMnO4​.

Thus, 0.005 eq. FAS has reacted.

The equivalent weight of FAS is 392 g.

0.005 equivalents of FAS corresponds to 0.005×392=1.96g of FAS.  

Hence, the percentage purity of FAS sample is 3.921.96​×100  or  50%.