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प्रश्न
How many moles of electrons are required for reduction of 2 moles of Zn2+ to Zn?
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उत्तर
The balanced equation for the reduction of Zn2+ to Zn is
\[\ce{Zn^{2+}_{ (aq)} + 2e- -> Zn_{(s)}}\]
The equation shows that 1 mole of Zn2+ is reduced to Zn by 2 moles of electrons.
For reduction of 2 moles of Zn2+, 4 moles of electrons will be required.
संबंधित प्रश्न
Define the following term:
Fuel cell
E°cell for the given redox reaction is 2.71 V
Mg(s) + Cu2+ (0.01 M) → Mg2+ (0.001 M) + Cu(s)
Calculate Ecell 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
If 'I' stands for the distance between the electrodes and 'a' stands for the area of cross-section of the electrode, `"l"/"a"` refers to ____________.
What is the SI unit tor electrochemical equivalent?
How many faradays of electricity are required for the following reaction to occur
\[\ce{MnO^-_4 -> Mn^2+}\]
A current strength of 3.86 A was passed through molten Calcium oxide for 41minutes and 40 seconds. The mass of Calcium in grams deposited at the cathode is (atomic mass of Ca is 40g/mol and 1F = 96500 C).
Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because ____________.
Assertion: pure iron when heated in dry air is converted with a layer of rust.
Reason: Rust has the compositionFe3O4.
In the electrochemical cell: Zn|ZnSO4 (0.01 M)||CuSO4 (1.0 M)|Cu, the emf of this Daniel cell is E1. When the concentration of ZnSO4 is changed to 1.0 M and that CuSO4 changed to 0.01 M, the emf changes to E2. From the above, which one is the relationship between E1 and E2?
Consider the change in the oxidation state of Bromine corresponding to different emf values as shown in the expression below:
\[\ce{BrO^-_4 ->[1.82 V] BrO^-_3 ->[1.5 V] HBrO ->[1.595 V] Br2 ->[1.0652 V] Br^-}\]
Then the species undergoing disproportionation is:
Cell equation: \[\ce{A + 2B^- -> A^{2+} + 2B}\]
\[\ce{A^{2+} + 2e^- -> A}\] E0 = +0.34 V and log10 k = 15.6 at 300 K for cell reactions find E0 for \[\ce{B^+ + e^- -> B}\]
Describe the electrolysis of molten NaCl using inert electrodes.
Describe the construction of Daniel cell. Write the cell reaction.
Why is anode in galvanic cell considered to be negative and cathode positive electrode?
Is it possible to store copper sulphate in an iron vessel for a long time?
Given: \[\ce{E^0_{{Cu^{2+}|{Cu}}}}\] = 0.34 V and \[\ce{E^0_{{Fe^{2+}|{Fe}}}}\] = −0.44 V
A copper electrode is dipped in 0.1 M copper sulphate solution at 25°C. Calculate the electrode potential of copper.
[Given: \[\ce{E^0_{{Cu^{2+}|Cu}}}\] = 0.34 V]
Electrode potential for Mg electrode varies according to the equation
`E_(Mg^(2+) | Mg) = E_(Mg^(2+) | Mg)^Θ - 0.059/2 log 1/([Mg^(2+)])`. The graph of `E_(Mg^(2+) | Mg)` vs `log [Mg^(2+)]` is ______.
Which of the following statement is correct?
Which of the following statement is not correct about an inert electrode in a cell?
Use the data given in below find out the most stable oxidised species.
`E^0 (Cr_2O_1^(2-))/(Cr_(3+))` = 1.33 V `E^0 (Cl_2)/(Cl^-)` = 1.36 V
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The quantity of charge required to obtain one mole of aluminium from Al2O3 is ______.
`E_(cell)^Θ` for some half cell reactions are given below. On the basis of these mark the correct answer.
(a) \[\ce{H^{+} (aq) + e^{-} -> 1/2 H_2 (g); E^Θ_{cell} = 0.00V}\]
(b) \[\ce{2H2O (1) -> O2 (g) + 4H^{+} (aq) + 4e^{-}; E^Θ_{cell} = 1.23V}\]
(c) \[\ce{2SO^{2-}_{4} (aq) -> S2O^{2-}_{8} (aq) + 2e^{-}; E^Θ_{cell} = 1.96V}\]
(i) In dilute sulphuric acid solution, hydrogen will be reduced at cathode.
(ii) In concentrated sulphuric acid solution, water will be oxidised at anode.
(iii) In dilute sulphuric acid solution, water will be oxidised at anode.
(iv) In dilute sulphuric acid solution, \[\ce{SO4^{2-}}\] ion will be oxidised to tetrathionate ion at anode.
`E_(cell)^Θ` = 1.1V for Daniel cell. Which of the following expressions are correct description of state of equilibrium in this cell?
(i) 1.1 = `K_c`
(ii) `(2.303RT)/(2F) logK_c` = 1.1
(iii) `log K_c = 2.2/0.059`
(iv) `log K_c` = 1.1
Can absolute electrode potential of an electrode be measured?
Depict the galvanic cell in which the cell reaction is \[\ce{Cu + 2Ag^+ -> 2Ag + Cu^{2+}}\]
Consider the following diagram in which an electrochemical cell is coupled to an electrolytic cell. What will be the polarity of electrodes ‘A’ and ‘B’ in the electrolytic cell?
A galvanic cell has electrical potential of 1.1V. If an opposing potential of 1.1V is applied to this cell, what will happen to the cell reaction and current flowing through the cell?
How will the pH of brine (aq. \[\ce{NaCl}\] solution) be affected when it is electrolysed?
Consider a cell given below:
\[\ce{Cu | Cu^{2+} || Cl^{-} | Cl_{2},Pt}\]
Write the reactions that occur at anode and cathode
Match the terms given in Column I with the units given in Column II.
| Column I | Column II |
| (i) Λm | (a) S cm-¹ |
| (ii) ECell | (b) m-¹ |
| (iii) K | (c) S cm2 mol-¹ |
| (iv) G* | (d) V |
Match the items of Column I and Column II.
| Column I | Column II |
| (i) K | (a) I × t |
| (ii) Λm | (b) `Λ_m/Λ_m^0` |
| (iii) α | (c) `K/c` |
| (iv) Q | (d) `G^∗/R` |
Assertion: Mercury cell does not give steady potential.
Reason: In the cell reaction, ions are not involved in solution.
The electrochemical cell stops working after some time because
A current of 2.0 ampere passed for 5 hour through a molten salt deposits 22 g of the metal (Atomic mass = 177). The oxidation state of the metal in the metal salt is
Standard reduction electrode potentials of three metals A, B and C are respectively + 0.5 V, – 3.0 V. and – 1.2 V. The reducing powers of there metal is.
Cell reaction is spontaneous when
If the half-cell reaction A + e– → A– has a large negative reduction potential, it follow that:-
If 0.5 amp current is passed through acidified silver nitrate then in 100 minutes the mass of silver, deposite on cathode is (eq. wt. of silver nitrate + 108).
In a Daniel cell, ______.
Read the passage given below and answer the questions that follow:
|
Oxidation-reduction reactions are commonly known as redox reactions. They involve transfer of electrons from one species to another. In a spontaneous reaction, energy is released which can be used to do useful work. The reaction is split into two half-reactions. Two different containers are used and a wire is used to drive the electrons from one side to the other and a Voltaic/Galvanic cell is created. It is an electrochemical cell that uses spontaneous redox reactions to generate electricity. A salt bridge also connects to the half-cells. The reading of the voltmeter gives the cell voltage or cell potential or electromotive force. If \[\ce{E^0_{cell}}\] is positive the reaction is spontaneous and if it is negative the reaction is non-spontaneous and is referred to as electrolytic cell. Electrolysis refers to the decomposition of a substance by an electric current. One mole of electric charge when passed through a cell will discharge half a mole of a divalent metal ion such as Cu2+. This was first formulated by Faraday in the form of laws of electrolysis.
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- Is silver plate the anode or cathode? (1)
- What will happen if the salt bridge is removed? (1)
- When does electrochemical cell behaves like an electrolytic cell? (1)
- (i) What will happen to the concentration of Zn2+ and Ag+ when Ecell = 0. (1)
(ii) Why does conductivity of a solution decreases with dilution? (1)
OR
The molar conductivity of a 1.5 M solution of an electrolyte is found to be 138.9 S cm2mol-1. Calculate the conductivity of this solution. (2)
On which electrode the oxidation reaction takes place?
If the value of Ksp for Hg2Cl2 (s) is X then the value of X will be ____ where pX = - log X.
Given:
\[\ce{Hg2Cl2 + 2e- -> 2Hg(l) + 2Cl-}\], E° = 0.27 V
\[\ce{Hg+2 + 2e- -> 2Hg(l)}\] E° = 0.81 V
Which of the following is incorrect?
The number of moles of electrons passed when the current of 2 A is passed through a solution of electrolyte for 20 minutes is ______.
Calculate the λ0m for Cl- ion from the data given below:
∧0m MgCl2 = 258.6 Scm2 mol-1 and λ0m Mg2+ = 106 Scm2 mol-1
What are electrochemical reactions?
Explain the types of electrochemical cells.
State the term for the following:
Two metal plates or wires through which the current enters and leaves the electrolytic cell.
