Science (English Medium) Class 12 - CBSE Important Questions

 Write the reaction that occurs at anode on electrolysis of concentrated 2 4 H SO using platinum electrodes. 

 Following reaction takes place in the cell: 
`Zn(s) + Ag_2O(s)+H_2O(l) -> Zn^{2+}(aq) + 2Ag (s) + 2OH^- (aq)`
Calculate `Delta_r G^0` of the reaction

[Given ; `E^0_(Zn^{2+}//Zn)` = -0.76V

`E_((Zn^{2+}//Zn)) = 0.76V`

`E_(Ag^4//Ag)^0 = 0.80V, 1F = 96,500 C mol^-1 ]`
          

 How can you determine limiting molar conductivity,   0 m for strong electrolyte and weak electrolyte?

A steady current of 2 amperes was passed through two electrolytic cells X and Y connected in series containing electrolytes FeSO₄and ZnSO₄ until 2.8g of Fe deposited at the cathode of cell X. How long did the current flow? Calculate the mass of Zn deposited at the cathode of cell Y. 
(Molar mass: Fe=56g mol^-1,Zn=65.3g mol^-1,1F=96500C mol^-1)

In the plot of molar conductivity (∧_m) vs square root of concentration (c^1/2) following curves are obtained for two electrolytes A and B : 

Answer the following:
(i) predict the nature of electrolytes A and B.
(ii) What happens on the extrapolation of ∧_m to concentration approaching for electrolytes A and B?

E°_cell for the given redox reaction is 2.71 V
Mg_(s) + Cu²⁺ _{(0.01 M)} → Mg²⁺ (0.001 M) + Cu_(s)

Calculate E_cell for the reaction. Write the direction of flow of current when an external opposite potential applied is
(i) less than 2.71 V and
(ii) greater than 2.71 V

Solve the following question.
A steady current of 2 amperes was passed through two electrolytic cells X and Y connected in series containing electrolytes FeSO₄ and ZnSO₄ until 2.8 g of Fe deposited at the cathode of cell X. How long did the current flow? Calculate the mass of Zn deposited at the cathode of cell Y.
(Molar mass : Fe = 56 g mol^–1, Zn = 65.3 g mol^–1, 1F = 96500 C mol^–1)

In the plot of molar conductivity (∧_m) vs square root of concentration (c^1/2), following curves are obtained for two electrolytes A and B:

Answer the following:
(i) Predict the nature of electrolytes A and B.
(ii) What happens on extrapolation of ∧_m to concentration approaching zero for electrolytes A and B?

Why on dilution the m Λ_m of \[\ce{CH3COOH}\] increases very fast, while that of \[\ce{CH3COONa}\] increases gradually?

Solutions of two electrolytes ‘A’ and ‘B’ are diluted. The Λ_m of ‘B’ increases 1.5 times while that of A increases 25 times. Which of the two is a strong electrolyte? Justify your answer. Graphically show the behavior of ‘A’ and ‘B’.

The molar conductivity of CH₃COOH at infinite dilution is 390 Scm²/mol. Using the graph and given information, the molar conductivity of CH₃COOK will be:

Why does the cell voltage of a mercury cell remain constant during its lifetime?

Write the reaction occurring at anode and cathode and the products of electrolysis of aq KCl.

Molar conductivity of substance “A” is 5.9 × 10³ S/m and “B” is 1 × 10^–16 S/m. Which of the two is most likely to be copper metal and why?

What is the quantity of electricity in Coulombs required to produce 4.8 g of Mg from molten MgCl₂? How much Ca will be produced if the same amount of electricity was passed through molten CaCl₂? (Atomic mass of Mg = 24 u, atomic mass of Ca = 40 u).

What is the standard free energy change for the following reaction at room temperature? Is the reaction spontaneous?

\[\ce{Sn(s) + 2Cu^{2+}(aq) -> Sn^{2+}(aq) + 2Cu+(s)}\]

Assertion (A) : Conductivity decreases with decrease in concentration of electrolyte.

Reason (R) : Number of ions per unit volume that carry the current in a solution decreases on dilution.

Assertion (A): Molar conductivity decreases with increase in concentration.

Reason (R): When concentration approaches zero, the molar conductivity is known as limiting molar conductivity.

The unit of molar conductivity is ______.

Which of the following solutions will have the highest conductivity at 298 K?