Redox Titration

Redox titration is a method used to determine the concentration of a substance by measuring the volume of a solution required to react completely with a known volume or mass of another substance.

In this case, we are given a solution of ferrous ammonium sulphate with a concentration of 0.3 M, and we need to determine the volume of this solution required to complete a redox titration with 20 ml of 0.1 M potassium dichromate solution.

Equation for the Reaction

The reaction between ferrous ammonium sulphate and potassium dichromate can be represented by the following balanced equation:

6 Fe(NH4)2(SO4)2 + K2Cr2O7 + 14 H2SO4 → 3 Fe2(SO4)3 + Cr2(SO4)3 + K2SO4 + 14 NH4HSO4 + 7 H2O

From the balanced equation, we can see that the ratio between the moles of ferrous ammonium sulphate and potassium dichromate is 6:1.

Calculating the Volume

To calculate the volume of the ferrous ammonium sulphate solution required, we need to use the following formula:

Moles of potassium dichromate = Moles of ferrous ammonium sulphate

Given that the volume of potassium dichromate solution used is 20 ml and its concentration is 0.1 M, we can calculate the moles of potassium dichromate used:

Moles of potassium dichromate = Concentration × Volume
= 0.1 M × 0.02 L
= 0.002 moles

Using the ratio from the balanced equation, we can determine the moles of ferrous ammonium sulphate:

Moles of ferrous ammonium sulphate = 6 × Moles of potassium dichromate
= 6 × 0.002 moles
= 0.012 moles

Finally, we can calculate the volume of the ferrous ammonium sulphate solution required:

Volume of ferrous ammonium sulphate solution = Moles / Concentration
= 0.012 moles / 0.3 M
= 0.04 L
= 40 ml

Therefore, the volume of the 0.3 M ferrous ammonium sulphate solution required for the completion of the redox titration with 20 ml of 0.1 M potassium dichromate solution is 40 ml.