Question

What are some ways you might measure the concentration of an unknown copper solution? (Other than using a voltmeter). Discuss the advantages and/or disadvantages of using the concentration cell.

Answer 1

To find the concentration an unknown copper solution, there are many techniques we can use.

For e.g.

i) Titration as a quantitative analysis technique

ii) Spectrophotometry as a quantitative analysis technique

i) Titration as a quantitative analysis technique: Copper (II) ions react with excess iodide ions to form a precipitate of copper (I) iodide and molecular iodine. We can titrate iodine against a standard solution of sodium thiosulfate, using starch indicator.

2Cu^2+(aq) + 4I^-(aq)   →   2Cul(s) + I2(aq)

I₂(aq) + 2S2O3^2-(aq)   → 2I-(aq) + S4O6^2-(aq)

ii) Spectrophotometry as a quantitative analysis technique –

We can determine the concentration of an unknown Copper solution by measuring its absorbance. By plotting the absorbance of the unknown on the vertical axis of the graph and the corresponding concentration on the horizontal axis, we can calculate the concentration of the copper solution by using   the Beer’s law

Advantages of using the concentration cell –

1) Concentration cells are used to measure the concentration gradients produce electrical current

ion pumps across cell membranes Na+ / K+ pump.

2) PH meter -measurement of the cell potential provides pH directly

Disadvantages of using the concentration is corrosion of a metal surface are in contact with different concentrations of the same solution.