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E^@ (standard electrode potential) value...

`E^@` (standard electrode potential) values generally become less negative as we move across a transition series. But `E^@`values of `Ni^2//Ni` and `Zn^(2+)//Zn` are exceptions. Justify.

Text Solution

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The values of `E^@` for `Ni^(2+)//Ni ` and `Zn^(2+)//Zn`are more negative than expected. The high negative value `E^@Ni^(2+)//Ni ` is due to the high enthalpy of hydration of `Ni^(2+)` + ions. This stabilises `Ni^(2+)`ions. The high negative value of `E^@Zn^(2+)//Zn` is due to the stable completely filled `3d^10` electronic configuration of `Zn^(2+)` ions.
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10. A student 'tried to find out the standard reduction'potentials of copper electrode and Zinc eleetrode separately using Normal Hydrogen Electrode as reference electrode. He obtained the reduction potentials of E^0 Cu^2 / Cu as 0.34 and E^prime zn^2+ / zn as- 0.76 . The, reference electrode acted here as cathode in one case and anode in theother.' 1. In which cases NHE acts as cathode and anode respectively. 2. Represent the electrode reactions of the NHE in both cases. 3. Represent the cell reaction when he used the Cu electrode and NHE. 4. Calculate the standard' potential of the cell constructed using Z_i n and Cu electrodes.

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Knowledge Check

  • The standard electrode potentials of Zn and Ni respectively are -0.76 V and -0.25 V. Then the standard emf of the spontaneous cell by coupling these under standard conditions is

    A
    `+1.01 V`
    B
    `-0.51 V`
    C
    `+0.51 V`
    D
    `+0.25 V`

  • In a conservative force field , we can find the radial component to force F from the potential energy function (U) using the relation F= (dU)/(dr) . Positive value of F mean repulsive force and vice-versa. We can find the equilibrium position, where force is zero. We can also calculate ioinisation energy, which is the work done to move the particle from a certain position to infinity. Let us consider a particle bound to a certain point at a distance r from the centre of the force. The potential energy function of the particle is given by U(r) = (A)/(r^(2)) - (B)/(r) where A and B are positive constants. The nature of equilibrium is

    A
    neutral
    B
    stable
    C
    unstable
    D
    cannot be predictable

  • In a conservative force field , we can find the radial component to force F from the potential energy function (U) using the relation F= (dU)/(dr) . Positive value of F mean repulsive force and vice-versa. We can find the equilibrium position, where force is zero. We can also calculate ioinisation energy, which is the work done to move the particle from a certain position to infinity. Let us consider a particle bound to a certain point at a distance r from the centre of the force. The potential energy function of the particle is given by U(r) = (A)/(r^(2)) - (B)/(r) where A and B are positive constants.

    A
    `r_(0)`
    B
    `(2r_(0))/(3)`
    C
    `(2r_(0))/(5)`
    D
    `(r_(0))/(3)`

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    The Standard electrode potentials of some electrodes are given below: E^@_(Zn^(2+)Zn) = -0.76 V, E^@(Cu^(2+)Cu) =+0.34, E^@_(Ag, Ag) = + 0.80V, E^@_(H, H_2)=0V What is the reaction taking place at SHE when it is connected to Ag/Ag^+. Electrode to form a galvanic cell?

    The cell reaction in Daniell cell is Zn(s) + Cu^(2+) (aq) to Zn^(2+)(aq) + Cu(s) and Nernst equation for single electrode potential for general electrode reaction M^+ (aq) + n e^(-) to M(s) is E_(M^(n+)//M)=E_(M^(n+)//M)^@- (2.303 RT)/(nF) log [[M]]/[[M^(n+)]] Derive Nernst equation for Daniell cell

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