Question

Experiment 9 Part C-Electrolysis of Salt Solutions 10. Obtain and thoroughly rinse a U-shaped glass tube (U-tube) and fill it to within an inch or so of the rim with the 2% NaCl solution. 11. Add one drop of phenolphthalein to each arm of the U-tube. Clamp the U-tube to a ring stand (Figure 9-2). 12. Obtain two graphite electrodes and rinse the electrodes thoroughly. Obtain two connector wires with alligator clamps on both ends. With one of the clamps on each wire secure the graphite electrodes and insert an electrode into each arm of the U-tube. Before connecting to the 9-V battery stir with each electrode to insure that the phenolphthalein has mixed well with the salt solution. Now connect the wires to the battery. **Note that you do not have to decide at this point which electrode will act as the cathode and which as the anode since the observations that we will make as the reaction proceeds will allow us to identify the cathode and the anode. 13. Give the reaction a few minutes to get going and then observe what is occurring at the two elec- trodes. Record your observations and decide which electrode is acting as the cathode and which as the anode. Based on the observed reactions that are taking place decide which half-reaction is occurring at each electrode. 14. Discard the solution and thoroughly rinse the U-tube and the electrodes with tap water and then distilled water. 15. Repeat the electrolysis for 2% Cuso, 2% KI, and 2% NaBr. Be sure to thoroughly rinse the U-tube and the electrodes after each electrolysis and discard the solutions in their appropriate waste container. Waste Disposal: All solutions may be rinsed down the drain.

Answer 1

* Electrolysis of salt solution ③ Nach caq) 7 observation Anode cathod H₂ observation' gas cla gas - cathode Half Reaction . 2 H2O +zé -> Hergj +.20H caq) * Ano de Half Reaction : a cê can cl + a é © Cus04(aq) = cathode observation Cu metal C Anode observation O2 gas : Cathode Half Reaction : aq) creatas, + 2e → Cu(s) Anode Half Reaction : 401 or 2 (g) + 2 H₂O ce, +4 é dupca)

3) KI call) > Anode observation ob a cathode observation Ha gas Anode Iz a cathode Half Reactions 2 H₂O estré → H2(g) + 2 otcaq). Anode Half Reaction; - I caq) → Iz caq) + 2e savas 4) NaBreag) Anode observation » Cathode H₂ observation gas B7, gas cathode Half reaction.i 2 Hoces + 2? tiré → Harg) + 20h (aq) Anode Half Reaction ; : » 2 Br(aq) → Br. (g) + 26.