Chemistry NCERT Exemplar Solutions Class 12th Chapter Three

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Ans: Acetic acid is a weak electrolyte and the number of ions on dilution increases due to an increase in the degree of dissociation. In the case of strong electrolytes the number of ions remains the same but interionic attraction decreases.

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Ans: The cell reaction of a lead storage battery is as follows;

Pb + PbO₂ + 2H₂SO₄→2H₂SO₄ + 2H₂O

The density of electrolytes changes because water is formed and sulphuric acid is consumed as a product during discharge of the battery

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Ans: Primary batteries contain a limited amount of reactants and once consumed are discharged. Secondary batteries take a long time to recharge. Fuel cells run continuously as long as reactants are supplied to them and products are consumed

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Ans: The reactions taking place in the Daniel cell is as follows;

Zn⁺ + Cu²⁺ → Zn²⁺ + Cu

The number of electrons involved in two. The Nernst equation is as follows;

E_{cell =} E $°$ _cell - $\frac{-0.059}{2}$  log $\frac{\left[Z{n^2}^{+}\right]}{\left[C{u^2}^{+}\right]}$

From the above equation, we conclude that increasing the concentration of Zn^2+, E_cell will decrease.

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Ans: The given cell reaction consists of two half cell reactions represented below as follows;

At anode: Cu→Cu²⁺+ 2e⁻

At cathode: Cl² + 2e⁻ →2Cl⁻

Here oxidation of copper and reduction of chlorine is taking place

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Ans: Standard hydrogen electrode (SHE) is used as a reference electrode and its electrode potential is assumed to be zero. The electrode potential of other electrodes is measured concerning standard hydrogen electrodes.

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Ans: Conductivity due to the total number of ions present in the solution is termed as specific conductivity. An increase in the number of ions per unit volume increases. In addition to water, the number of ions per unit volume decreases therefore conductivity decreases.

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Ans: pH of the substance depends on the concentration of hydronium ions present. Here the concentration of hydronium ions remains constant so pH remains constant.

The electrolysis reaction is as follows;

At anode: 2H₂O (l)→O₂ (g)+ 4H⁺ + 4e−

At cathode:4H⁺ + 4e⁻ →2H₂

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Ans: Stronger electrolytes undergo cent percent dissociation. Electrolyte B will be the stronger electrolyte since the concentration of ions remains the same upon dilution.

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Ans: The number of ions present in the cell decides the life-time of any cell. In mercury cells, ions are not involved so the mercury cell has a constant cell potential throughout its useful life.