Question

Consider four different samples: aqueous NaBr, molten NaBr, aqueous NaF, and molten NaF. Current run through each sample produces one of the following products at the anode: liquid bromine, fluorine gas, or oxygen gas. Match each sample to its anodic product.

Answer 1

Answer:

Aqueous NaBr - oxygen gas

Molten NaBr - liquid bromine

Aqueous NaF- oxygen gas

Molten NaF - Flourine gas

Explanation:

In electrolysis process, anode is the positive electrode and cathode is the negative electrode.

Hence negative ions are attracted towards anode and gets oxidized.

When more than one type of ion is present , the ion which gets deposited is decided by the discharge potential.

Discharge potential is the voltage at which an ion is discharged.The ion that requires less energy to get deposited has low discharge potential.

Hence ion with low discharge potential gets deposited.

Discharge potential is in the order: $F^->Br^->OH^-$

1. In aqueous NaBr , there are two negative ions:Br- and OH-      

OH- is oxidized to oxygen gas as OH- has lower discharge potential.            

    2. In molten NaBr, Br- is the only negative ion and liquid bromine is                    produced at anode.

    3. In aqueous NaF, OH- and F- are the anions present. Clearly oxygen gas is produced at anode as OH- has lower discharge potential.

    4. In molten NaF only anion present is F- and hence flourine gas is produced at anode.