Question

Small Scale Pilot Plant (for the manufacture of a) Straws a cap small drop of Starch/kt anode (where oxidation OCUYS) cathode N I NO (where percobado reduction lead OCCOYS) brine & 3 drops of phenolphthalein well redox reaction at the cathode (purple liquid formed in the straw) 2 H2O cesta e He (g) +204 cag) • redox reaction at the anode 2015,(126gt 2 e Q What is the balanced reaction for the redox reaction accomplished during this electrolysis? Also, why we need to cap the anode straw but not the cathode s Straw (please with details) I already know water is reduced into OH and H₂, Cl- is oxidized into Cl2, etc

Answer 1

Electrolysis of aq.NaCl=

Electrolysis of aq. NaCl results in H2 gas  and Cl2 gas formation.

At the anode,chloride (Cl-) ion is oxidized to chlorine gas.

The ion-selective membrane allows the counterion Na+ to freely flow across, but prevents anions such as hydroxide (OH-) and chloride from diffusing across. At the cathode,water is reduced to hydroxide and hydrogen gas. The net process is the electrolysis of an aqueous solution of NaCl into NaOH and chlorine gas.

The reaction at the cathode is:

H2O (liq) + 2 e- ---------》 H2-(g) + 2OH-

The reaction at the anode is:

Cl- ----‐》 1/2 Cl2- (g) +1e-

The overall reaction is,

2NaCl(aq) + 2H2O(liq) ----------》   2Na+(aq) + 2OH- (aq) + H2- (g) + Cl2 gas.

Capping at Anode -

The main reason for capping at anode side is  the gas generated.chlorine gas is highly poisonous and classified as a pulmonary irritant. It has intermediate water solubility with the capability of causing acute damage to the upper and lower respiratory track of human being. So avoid environmental or human contact anode side get capped.

While on cathod side Hydroge gas liberated and is not toxic to human and environment.