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(2)

1litre of 2.1M HCl solution is taken and 965 amperes of current is passed for 200sec What is the pH of residual solution

a).3010b)2c)1d).1

karanp1

the answer is 1

heres how
the soln is 2.1 M and we have one litre so in effect we have 2.1 moles
Since HCl is a monobasic acid so 2.1 moles = 2.1 equivalents

We have passed charge , q = i x t = 2 x 96500

For the electrolysis of 1eq we need 96500 coulombs but we are passing double of that charge so 2 eq of H+ gets liberated which combines and forms H2 gas which is released at an electrode

Now we have 2.1 - 2 = .1 eq = .1 moles of HCl left which will dissociated fully to give .1 moles of H+ in one litre of soln

therefore pH = -log[H+] = - log (.1) = -log {10^(-1)} = 1

smriti.mathur

(c) 1

Quantity of electricity used,

Q = I * t

where, I = current in amperes

t = time in seconds

Q = 965 * 200 coulombs

1 Faraday = 965 * 200 / 96500 = 2

2 Faraday electricity is passed

Now, 1 Faraday discharges 1 equivalent ions (Faraday's law)

2 equivalents of H⁺ ions have gone to cathode

Remaining equivalents of H⁺ ions = 2.1 - 2 = 0.1

= 10^-1 /ltr

Therefore, pH = 1 (pH is negative of the power of 10 which expresses H⁺ concentration)

karanp1

didnt I give the same answer . what is the point of giving the same answer

chimanshu_007

hey dude listen.............

this is a qs fr the experts so it must b answered by the experts and thats wat mam did here

i appreciate ur ans and i m giving u a arate but i say it has to b answered by experts
and u never know that student understand ur method or not.............

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