Question

To 8.00 mL support electrolyte was added 0.500 mL of diphenylamine, which after deaeration gave a current of 65.7 mA. After adding 0.200 mL standard solution of 1000 ppm diphenylamine, the new current signal was 78.5 mA. (i) What is the concentration of diphenylamine in the electrolytic cell? (ii) What the the concentration of diphenylamine in the original sample?

Answer 1

Given data:

Volume of electrolytic solution = 8 mL

Volume of diphenylamine = 0.5 mL

Volume of 1000 ppm diphenylamine = 0.2 mL

i.e. The total volume = 8.7 mL

In addition, the molar mass of diphenylamine = 169 g mol^-1 and density = 1.2 g/mL

(ii) The cocentration of diphenylamine in the original standard sample = (1000 mg/L)/169 g mol^-1

= 5.917*10^-3 mol/L (or) 5.917 mmol/L

(i) The concentration of diphenylamine in the electrolytic cell = (1.2*0.5 g/169 g mol^-1) / 8.7*10^-3 L

= 4.081*10^-1 mol/L (or) 4.081*10^-1 M