Question

Consider four different samples: aqueous LiBr, molten LiBr, aqueous AgBr, and molten AgBr. Current run through each sample produces one of the following products at the cathode: solid lithium, solid silver, or hydrogen gas. Match each sample to its cathodic product. Drag the appropriate items to their respective bins.

Answer 1

Answer:

• aqueous LiBr → hydrogen gas
• molten LiBr → solid lithium
• Aqueous AgBr → solid silver
• molten AgBr → solid silver

Explanation:

Electrolysis is a process in which an electric current is passed through an electrolyte in an electrolytic cell. The electrolyte maybe in aqueous form or in molten state. The electrolyte is an ionic compound, so during electrolysis, the anions move towards anode while the cations move towards the cathode. Oxidation takes place at the anode. While reduction takes place at the cathode.

In the molten form, only the constituent ions are present to be oxidized or reduced. Thus, in electrolysis of molten LiBr, lithium is reduced at the cathode and bromine is oxidized at the anode.

$Li^{+}$(aq) + $e^{-}$ → Li(s)

Solid Lithium is produced at the cathode

Similarly, solid Silver is produced at the cathode during electrolysis of molten AgBr:

$Ag^{+}$(aq) + $e^{-}$ → Ag(s)

However, in aqueous form, $H_{2} O$ ions and LiBr ions compete with each other. Since H+ has a greater standard redox potential than lithium,H+ will be reduced at the cathode to produce hydrogen gas

$2H^{+}$(aq) + $2e^{-}$ → $H_{2}$(g)

Similarly,in aqueous AgBr, Ag will be produced at the cathode because the standard redox potential for Ag+ is higher than H+ .

$Ag^{+}$(aq) + $e^{-}$ → Ag(s)