ELECTROLYSIS OF SOME ELECTROLYTES ELECTROLYSIS OF CONCENTRATED SODIUM CHLORIDE SOLUTION (BRINE) USING GRAPHITE ANODE

At the anode: Both Cl^– and OH^– migrate to the anode on passing direct current to compete for discharge. Cl^– ion being more electronegative and having a high concentration in is discharged in preference to the hydroxide ion, OH^–, by loss of electron to produce chlorine atom. Chlorine atoms pair to form chlorine gas.

At the cathode: Both Na⁺ and H⁺ migrate to the cathode on passing direct current to compete for discharge. H⁺ being far below Na⁺and less electropositive is discharged by accepting electrons to produce neutral hydrogen atoms which pair up to produce hydrogen gas. Na⁺ concentration is high but it is very electropositive and so not discharged.

The resulting solution becomes more alkaline in NaOH as concentration of Na⁺ and OH^– increase.

EVALUATION

1.         Describe the electrolysis of dilute sodium chloride solution.

2.         What is the condition of the final solution?

ELECTROLYSIS OF DILUTE H₂SO₄ (ACIDIFIED WATER)

Acidified water is prepared by adding a few drop of tetraoxosulphate VI acid to water. It is a dilute H₂SO₄.

TROLYSIS OF COPPER (II) TETRAOXOSULPHATE (VI) SOLUTION (USING DIFFERENT ELECTRODES)

GENERAL EVALUATION/REVISION

1.     State the products formed as the electrode during the electrolysis of CuSO₄solution using Cu anode

2.      Write balanced half equations for the electrolysis of dilute H₂SO₄.

3.      Describe the electrolysis of dilute sodium chloride solution and state the condition of the final solution.

4.      Define the following terms: Atoms, Molecules and Ions.

5.      State the Dalton’s atomic theory and its modifications.

READING ASSIGNMENT

New School Chemistry for Senior Secondary Schools by O. Y. Ababio, pages 205-207

WEEKEND ASSIGNMENT

SECTION A: Write the correct option ONLY

1.        Metal X will be above metal Y in the activity series if X

A.         Displaces ions of Y from solution

B.         Has a higher boiling point than Y

C.         Has a higher melting point than Y

D.         Has a higher relative atomic mass than Y

2.         What will happen at the anode when copper II tetraoxosulphate VI solution is electrolyses using platinum electrode

A.         Copper is dissolved                  B.         Copper metals is deposited

C.         hydrogen is discharged            D.         Oxygen gas is produced

3          Oxidation takes place at the anode during electrolysis because anode

            A.         Is deficient in electrons            B.         is different in protons

            C.         has excess electrons            D.            has attraction for positive ions.

4          What product is formed at the cathode during the electrolysis of concentration sodium chloride solution using carbon electrode             A.         Chlorine           B.         hydrogen         C.         oxygen             D.         sodium

SECTION B

1.     State TWO differences between a conductor and an electrolyte. 2.     Describe the electrolysis of CuSO₄ solution using platinum electrode.