Electrochemistry · Question 25

On charging the lead storage battery, the oxidation state of lead changes from x1 to y1 at the anode and from x2 to y2 at the cathode. The values of x1, y1, x2, y2 are respectively :

1. 0, +2, +4, +2
2. +2, 0, 0, +4
3. +4, +2, 0, +2
4. +2, 0, +2, +4

The molar conductance of an infinitely dilute solution of ammonium chloride was found to be 185 S cm2 mol-1 and the ionic conductances of hydroxide and chloride ions are 170 and 70 S cm2 mol-1, respectively. If molar conductance of 0.02 M solution of ammonium hydroxide is 85.5 S cm2 mol-1, its degree of dissociation is given by x 10-1. The value of x is . (Nearest integer)

Correct order of limiting molar conductivity for cations in water at 298 K is :

1. H+ > Na+ > K+ > Ca2+ > Mg2+
2. H+ > Ca2+ > Mg2+ > K+ > Na+
3. Mg2+ > H+ > Ca2+ > K+ > Na+
4. H+ > Na+ > Ca2+ > Mg2+ > K+

The standard cell potential ( E cell ) of a fuel cell based on the oxidation of methanol in air that has been used to power television relay station is measured as 1.21 V. The standard half cell reduction potential for O2 ( E O2/H2O ) is 1.229 V. Choose the correct statement :

1. Reactants are fed at one go to each electrode.
2. Oxygen is formed at the anode.
3. The standard half cell reduction potential for the reduction of CO2 ( E CO2/CH3OH ) is 19 mV
4. Reduction of methanol takes place at the cathode.

40 mL of a mixture of CH3COOH and HCl (aqueous solution) is titrated against 0.1 M NaOH solution conductometrically. Which of the following statement is correct? [figure]

1. The concentration of CH3COOH in the original mixture is 0.005 M
2. The concentration of HCl in the original mixture is 0.005 M
3. CH3COOH is neutralised first followed by neutralisation of HCl
4. Point 'C' indicates the complete neutralisation of HCl

Consider the following electrochemical cell at standard condition. Au(s) | QH2, Q | NH4X(0.01 M) || Ag+(1 M) | Ag(s) Ecell = +0.4 V The couple QH2/Q represents quinhydrone electrode, the half cell reaction is given below: [figure] [Given : E0 Ag+/Ag = +0.8 V and 2.303RTF = 0.06 V] The pKb value of the ammonium halide salt (NH4X) used here is . (nearest integer)

0.2\% (w/v) solution of NaOH is measured to have resistivity 870.0 m m. The molar conductivity of the solution will be 102 mS dm2 mol-1. (Nearest integer)

For a Mg | Mg2+(aq) || Ag+(aq) | Ag the correct Nernst Equation is :

1. Ecell = E cell - RT2F [Ag+]2[Mg2+]
2. Ecell = E cell - RT2F [Mg2+][Ag+]
3. Ecell = E cell - RT2F [Ag+][Mg2+]
4. Ecell = E cell + RT2F [Ag+]2[Mg2+]

The molar conductivity of a weak electrolyte when plotted against the square root of its concentration, which of the following is expected to be observed?

1. Molar conductivity increases sharply with increase in concentration.
2. Molar conductivity decreases sharply with increase in concentration.
3. A small increase in molar conductivity is observed at infinite dilution.
4. A small decrease in molar conductivity is observed at infinite dilution.

Given below is the plot of the molar conductivity vs concentration for KCl in aqueous solution. [figure] If, for the higher concentration of KCl solution, the resistance of the conductivity cell is 100 , then the resistance of the same cell with the dilute solution is 'x' . The value of x is (Nearest integer)