n order to determine the concentration of bivalent nickel in environmental samples we can use the complexometric titration. A 100 mL sample containing Ni2 + was treated with 50 mL of 0.02 mol / L EDTA solution complexing all Ni2 + solution and leaving an excess of EDTA in the solution for subsequent retro-titration with a standard of Zn2 + 0.05 mol / L . In the retro-titration, 10 mL of standard Zn2 + solution was expended until the titration endpoint. Determine the nickel concentration in the sample

Question

n order to determine the concentration of bivalent nickel in environmental samples we can use the complexometric titration. A 100 mL sample containing Ni2 + was treated with 50 mL of 0.02 mol / L EDTA solution complexing all Ni2 + solution and leaving an excess of EDTA in the solution for subsequent retro-titration with a standard of Zn2 + 0.05 mol / L . In the retro-titration, 10 mL of standard Zn2 + solution was expended until the titration endpoint. Determine the nickel concentration in the sample

Answer 1

mols EDTA total = M x L = ?

,p;s EDTA back titrated = ?
Difference is mols Ni and (Ni^2+) = mols/L
I assume you know that EDTA complexes with both Zn and Ni 1:1

Answer 2

To determine the concentration of bivalent nickel (Ni2+) in the sample using complexometric titration, we need to calculate it based on the amount of standard Zn2+ solution required for retro-titration.

Let's break down the steps involved:

1. Complexation of Ni2+ with EDTA (Ethylene Diamine Tetraacetic Acid):
- A 100 mL sample containing Ni2+ is treated with 50 mL of 0.02 mol/L EDTA solution. The EDTA forms a complex with Ni2+, converting all of the Ni2+ in the sample into the Ni2+-EDTA complex.
- The excess EDTA that is not complexed with Ni2+ remains in the solution.

2. Retro-titration with standard Zn2+ solution:
- The excess EDTA in the solution is then titrated back with a standard Zn2+ solution.
- In this case, 10 mL of a standard 0.05 mol/L Zn2+ solution is used for the retro-titration.
- The Zn2+ reacts with the excess EDTA in a 1:1 stoichiometric ratio to form a Zn2+-EDTA complex.

3. Determining the nickel concentration:
- The amount of Zn2+ used in the retro-titration is correlated to the amount of excess EDTA in the solution.
- Since the excess EDTA is in a 1:1 stoichiometric ratio with the Ni2+-EDTA complex formed in the first step, the amount of Zn2+ used is also directly related to the amount of Ni2+ in the sample.
- By calculating the concentration of Ni2+ based on the volume and concentration of the Zn2+ solution used, we can determine the nickel concentration in the original sample.

To calculate the nickel concentration:

1. Determine the moles of Zn2+ used in the retro-titration:
Moles of Zn2+ = volume of Zn2+ solution (in L) x concentration of Zn2+ solution (in mol/L)

2. Since the Zn2+ solution and the excess EDTA react in a 1:1 stoichiometric ratio, the moles of Zn2+ used in the retro-titration represent the moles of excess EDTA in the sample.

3. Calculate the moles of Ni2+ in the sample:
Moles of Ni2+ = moles of Zn2+ used in retro-titration

4. Calculate the concentration of Ni2+ in the sample:
Concentration of Ni2+ = moles of Ni2+ / volume of sample (in L)

By following these calculations, you can determine the concentration of bivalent nickel (Ni2+) in the given environmental sample.