Author Topic: Electrolysis/Faraday law question (Read 1047 times) Tweet Share

diam0nds · « **on:** September 13, 2012, 05:43:28 pm »

We just started electrolysis (last chapter yay) today and I'm having trouble with one of the questions my teacher gave us to do for homework :S

A scientist wishes to experimentally verify Avagadro's constant by electrolytic means. To achieve this, a current of 1.217 A is passed for precisely 5 minutes 38 seconds through an electrolytic cell containing inert electrodes and an electrolyte solution of nickel sulfate. After the current has been passed, the mass of nickel deposited is 0.1252 g. The charge carried by one electron is 1.602 X 10^-19 C. Use this data to determine Avagadro's constant.

I'm just confused with what to do with the 1.602 x 10^-19

Conic · « **Reply #1 on:** September 13, 2012, 05:58:55 pm »

You have been given the charge of one electron (in coulombs), and the current (coulombs per second) and the time (in seconds).
You can use them to find the amount of electrons it takes to form 0.1252g of the Nickel.

dinosaur93 · « **Reply #2 on:** September 16, 2012, 09:48:54 am »

Ok....firstly, lay out all the given information and formulas

$1. Q = It$
$2. Q = n_e_^-$ $F$
$3. N_A = \frac {F}{electronic charge}$

$I = 1.217 A$

$t = 5 mins 38 secs = (5 \times 60) + 38 = 338 secs$

$1. Q = It$

$1. Q = 1.217 \times 338 = \mathbf{411.3 C}$

$F = 96500 C$

$Ni ^2^+ + 2e^- \longrightarrow Ni$

$\frac {n (Ni)}{n (e^-)} = \frac{1}{2}$

$\therefore n(e^-) = 2n(Ni)$

$2 \times \frac{m(Ni)}{Mr(Ni)} = 2 \times \frac{0.1252}{58.7} = \mathbf {4.26 \times 10^-^3 mol}$

$2. Q = n_e_^-$ $F$

$F = \frac{Q}{n_e_^-F}$ = $\frac {411.26}{4.26 \times 10^-^3}$ = $\mathbf {96429 C mol^-^1}$

electronic charge = $1.602 \times 10^-^1_9$

$F = 96429 C mol^-^1$

$3. N_A = \frac {F}{electronic charge}$

$3. N_A = \frac {96429}{1.602 \times 10^-^1_9} = \mathbf {6.020 \times 10^2^3}$ as required

hope this helps...

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Author Topic: Electrolysis/Faraday law question (Read 1047 times) Tweet Share

diam0nds

Electrolysis/Faraday law question

Conic

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dinosaur93

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