Question

Name: Electrochemistry and Equivalent Mass Figure 4: Electrolysis of NaCl(a) "brine" solution. 4. Refer to figure 4, an illustration of the electrolysis of a NaCl(aq) solution, called a brine". This method is used to manufacture chlorine gas and sodium hydroxide. Chlorine is widely used to purify water, as a disinfectant, and in the making of important compounds such as chloroform, a compound used in the production of Teflon. Chloride ions are oxidized in the anode half-cell and water is reduced in the cathode half-cell. A diaphragm that allows sodium ions to migrate from the anode to the cathode separates the two half- cells. NaCI(aq) DC Power Supply new brine cla H2 Cathode H2O но Diaphragm Sodium Hydroxide C is exidized. HO is Reduced. a) Write the balanced net-ionic equations for the two half-reactions that occur in this cell. Include phase labels. b) Write the balanced complete reaction (include spectator ions) for the overall redox reaction that occurs in this cell. Include phase labels. c) Determine the equivalent mass of water for this reaction. d) Explain clearly and completely why sodium ions must be able to migrate across the diaphragm from the anode hal cell into the cathode half-cell.

Answer 1

d) During the electrolysis of brine, gradually chloride ions are converted into chlorine gas, H⁺ ions from water produce hydrogen gas. -OH^- are also formed from water and they combine with Na⁺ ions in aqueous phase.

41 a) Anode half cell Oxidation at anode 2 CA ( ag) Cathode half -cel) Reducion at cathode (ag) bThus the ovezall Reaction is (as Ovena) xeaction including spectaton ions 2(3) 2(3 C) Equivalent mass t wak elect of bhine Solution At cathode :-240(1)+2C5 2 moleろ ele(hons. Moleculanmass Equiva lent mass no ot elec hons ained pemle 18gh。) /1 1829uiral -Bequival ", Equivalent mass of 4,0 =

Both the H₂ gas and Cl₂ gas may combine and the reaction is explosive. So to avoid this reaction, the cathode must be surrounded by a porous diaphragm made of asbestos.

The diaphragm is chosen in such a way that it allows the flow of Na⁺ ions from anode. Then the Na⁺ ions combine with OH^- ions formed in cathode cell.

The electrolyte brine gradually converts into sodium hydroxide solution.