Home
Class 12
CHEMISTRY
The emf of a cell corresponding to the r...

The emf of a cell corresponding to the reaction
`Zn +2H^(+)(aq) rarr Zn^(2+) (0.1M) +H_(2)(g) 1` atm is `0.28` volt at `25^(@)C`. Calculate the `pH` of the solution at the hydrogen electrode.
`E_(Zn^(2+)//Zn)^(@) =- 0.76` volt and `E_(H^(+)//H_(2))^(@) = 0`

A

7.05

B

8.62

C

8.75

D

9.57

Text Solution

Verified by Experts

The correct Answer is:
B
The half-cell reaction are `Zn to Zn^(2+) + 2e^(-)`
`2H^(+) + 2e^(-) to H_2 `
We know that
`E_(Zn//Zn^(2+))=E_(Zn//Zn^(2+))^@-"RT"/"nF""In"([Zn^(2+)])/([Zn])`
`therefore E_(Zn//Zn^(2+))=0.76-(2.303xx8.314xx298)/(2xx96500)"log"0.1/1`
=0.76-(-0.03)=0.79 V
Also, `E_(H^(+)//H_2)=E_(H^(+)//H_2)^@-"RT"/"nF""In"([H_2])/([H^+]^2)`
`=0-(2.303xx8.314xx298)/(2xx96500)"log"1/([H^+]^2)`
=0.0591 log `[H^+]` =-0.0591 pH
Since `E_"cell"=E_(Zn//Zn^(2+))+E_(H^+//H_2)`
or 0.28=0.79-0.0591 pH
or `pH=(0.79-0.28)/0.0591=0.51/0.0591`=8.62
Promotional Banner

Topper's Solved these Questions

  • ELECTROCHEMISTRY

    NCERT FINGERTIPS|Exercise HOTS|1 Videos

  • ELECTROCHEMISTRY

    NCERT FINGERTIPS|Exercise NCERT Exemplar|17 Videos

  • ELECTROCHEMISTRY

    NCERT FINGERTIPS|Exercise Corrosion|1 Videos

  • COORDINATION COMPOUNDS

    NCERT FINGERTIPS|Exercise Assertion And Reason|15 Videos

  • GENERAL PRINCIPLES AND PROCESSES OF ISOLATION OF ELEMENTS

    NCERT FINGERTIPS|Exercise Assertion And Reason|15 Videos

Similar Questions

Explore conceptually related problems

The emf of a cell corresponding to the reaction. Zn(s)+ 2H^(+)(aq)rightarrow Zn^(2+)(0.1M)+H_(2) (g,1atm) is 0.28 V at 25^(@) C . Calculate pH of the solution.

Emf of a cell corresponding to the reaction:- Zn(s) +2H^(+) (aq) rarr Zn^(2+)(aq) [0.1M] +H_(2)(g) [1.0atm] is 0.49V at 25^(@)C, E_(Zn^(2+)//Zn)^(@) = - 0.76 V . The pH of solution in cathode chamber is.

The emf of a cell corresponding to the following reaction is 0.0199 V at 298 K. Zn(s) + 2H^(+)(aq) rightarrow Zn^(2+)(0.1M) + H_(2)(g)(E_(Zn//Zn^(2+))^(@) = 0.76V The approximate pH of the solution at the electrode where hydrogen is being produced is [pH_(2) = 1 atm] :

For the cell Zn(s) + 2H^(+)(aq) rightarow Zn^(2+)(aq) + H_(2)(g) , E^(@) = 0.76 V Which change will increase the voltage of the cell?

The e.m.f. of a cell corresponding to the reaction : Zn_((s))+2H_((aq.))^(+) rarr underset((0.1 M))(Zn^(2+))+underset((1 atm))(H_(2(g)) is 0.28 V at 25^(@)C and E_(Zn//Zn^(2+))^(@) = 0.76V . (i) Write half cell reactions. (ii) Calculate pH of the solution at H electrode.