In the electrolysis of brine, the substances produced at the cathode are oxygen gas and hydroxide ions sodium metal and hydrogen gas chlorine gas and hydrogen gas hydrogen gas and hydroxide ions

In the electrolysis of brine, the substances produced at the cathode are sodium metal and hydrogen gas.

Explanation:

In the electrolysis of brine (Sodium chloride solution) using carbon as electrode, Chlorine gas is produced in the positive electrode (anode), while hydrogen gas is produced in the negative electrode (cathode).

Again, in the electrolysis of molten sodium chloride, chlorine gas is produced in anode, while sodium metal is produced in the cathode.

Nacl ⇄ Na⁺ + Cl⁻

Case 1: Molten Nacl

Anode(+ve) Product                              |    Cathode (-ve) product  

Cl⁻ > Cl + e⁻                                      |   Na⁺ + e⁻ > Na

Cl + Cl > Cl₂

Case 2: Nacl solution

Anode(+ve) Product                              |    Cathode (-ve) Product

Cl⁻ > Cl + e⁻                                      |   H⁺ + e⁻ > H

Cl + Cl > Cl₂                                     |   H + H > H₂

Thus, cathodic products of electrolysis of brine are sodium metal and hydrogen gas                                

chlorine gas and hydrogen gas

Explanation:

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)