Question

What is Nernst equation? The emf of a cell measured by means of a
hydrogen electrode against a saturated calomel electrode at 298K is
0.4188 V. If the pressure of the H, (g) was maintained at latm, calculate
the pH of the unknown solution, given potential of reference calomel
electrode is 0.2415 V.​

Answer 1

Answer:

Ecell=E°cell-0.0591÷n×(logQ)

Answer 2

Answer:

The pH of the solution is 0.57

Explanation:

The Nernst equation is used to determine the concentration of one of the cell's components or to compute the voltage of an electrochemical cell.

The Nernst equation is:

$E_{cell} = E_{0cell} - (\frac{RT}{nF} ) log Q$

$E_{cell}$ = cell potential under nonstandard conditions (V)

$E_{0cell}$ = cell potential under standard conditions

T = temperature (K) , R = gas constant, which is 8.31 $(\frac{volt - columb}{mol - k} )$

n = number of moles of electrons exchanged in the electrochemical reaction (mol) , F = Faraday's constant, 96500 coulombs/mol ,

Q = reaction quotient, where beginning concentrations are used in place of equilibrium concentrations in the equilibrium expression.

First calculate the potential of hydrogen electrode:

E = $E_{calomel} - E_{hydrogenelectrode}$

0.4188 = 0.2415 - $E_{HE}$

$E_{HE}$ = 0.2415 - 0.4188

$E_{HE}$ = - 0.1773

Now calculate the hydrogen ion concentration.

$E_{HE} = E^{0}_{H} - (\frac{RT}{nF} ) log\frac{pH_{2} }{[H^{+} ]^{2} }$

-0.1773 = 0 - ($\frac{8.31 * 298}{2 * 96500}$)

-0.1773 = - $(\frac{2476.38}{193000} ) log(\frac{1}{[H^{+} ]^{2} } )$

0.1773 =  0.0128 $log\frac{1 }{[H^{+} ]^{2} }$

$[H^{+}]$ =  3.721 M

Hence, the pH of the solution is pH = -log$[H^{+}]$ = -log(3.721)

the pH of the solution is 0.57

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