Class 12th

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A. The reaction has a zero order. The concentration of the reactants does not change with time in a zero order reaction, and the rate of concentration remains constant

B. Slope of the curve is  - k

C. The rate constant's units are molL  ¹s ^{- 1}

This is a Short Answer Type Questions as classified in NCERT Exemplar

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

This is a Short Answer Type Questions as classified in NCERT Exemplar

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

This is a Short Answer Type Questions as classified in NCERT Exemplar

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.

This is a Short Answer Type Questions as classified in NCERT Exemplar

Ans: Electrolysis of brine solution is as follows

NaCl (aq)→Na⁺ (aq)+Cl⁻ (aq)

At the cathode, the reaction goes this way,

H₂O (l) + e⁻→12H₂ (g)+OH⁻ (aq)

At the anode, the reaction goes this way,

Cl⁻ (aq)→12Cl₂ (g) + e⁻

The pH of the solution will increase as sodium hydroxide is being formed.

This is a Short Answer Type Questions as classified in NCERT Exemplar

Ans: When the opposing potential becomes equal to the electrical potential there is no current flowing in the cell and the cell reaction stops and there is no chemical reaction in the cell

This is a Short Answer Type Question as classified in NCERT Exemplar

The concentration of the reactants does not change with time in a zero -order reaction, and the rate of concentration remains constant. The molecularity of a reaction cannot be 0 because it indicates the number of reactants involved.

This is a Short Answer Type Questions as classified in NCERT Exemplar

Ans: Alternating current is used to stop electrolysis so that the concentration of the ions in the solution remains constant.

This is a Short Answer Type Questions as classified in NCERT Exemplar

Ans: The cell represented above shows an electrochemical cell in which two different electrodes are present and the cell at the bottom represents the electrolytic cell.

In this zinc is losing electrons moving towards electrode A and copper is accepting an electron from electrode B. Therefore, the polarity of electrode A is positive and electrode B is negative.