Question

# (i) Explain, why copper, though a good conductor of electricity, is a non-electrolyte. (ii) Name the gas released at the cathode when acidulated water is electrolysed. (iii) Explain, why solid sodium chloride does not allow electricity to pass through? (iv) Fill in the blanks: (a) As we descend the electrochemical series containing cations, the tendency of the cations to get _________ (oxidized/reduced) at the cathode increases. (b) The (higher/lower) __________ the concentration of an ion in a solution, the greater is the probability of its being discharged at its appropriate electrode.

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Solution

## (i) An electrolyte is in aqueous or molten state, as mobile ions are present in these states (both cations and anions). But solid copper metal lacks mobile ions, that are necessarily required for being an electrolyte. Thus, copper, though a good conductor of electricity, is a non-electrolyte. (ii) When acidulated water is electrolysed, hydrogen gas is released at cathode. The reaction at cathode is given below: ${\mathrm{H}}^{+}+{\mathrm{e}}^{-}\to \mathrm{H}\phantom{\rule{0ex}{0ex}}\mathrm{H}+\mathrm{H}\to {\mathrm{H}}_{2}$ (iii) In solid sodium chloride, ions (i.e. sodium cations and chloride anions) are tightly bound by electrostatic force of attraction and are not free to conduct electricity. Thus, solid sodium chloride does not allow electricity to pass through it. (iv) (a) As we descend the electrochemical series containing cations, the tendency of the cations to get reduced at the cathode increases. (b) The higher the concentration of an ion in a solution, the greater is the probability of its being discharged at its appropriate electrode.

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