[leena]

question
When an aqueous 0.1 mol dm^-3 Na₂SO₄ solution is electrolysed,12.044 *10^22 H₂ (g) molecules were produced,O₂(g) is the only other product formed.Given that the relative atomic mass of oxygen is 16, the other information required to calculate mass of O₂(g) produced is/are,
(1) Faraday's laws of electrolysis             (2) Avagadro constant
(3) Universal Gas constant                      (4) Faraday constant

so,
to find the mass of 02,
 reaction at cathode
2H⁺ + 2e H2

at anode
4OH^- O2 + 2H2O + 4e

 using avagadro's const
6.022*10^23 molecules of H2 2g of H2
12.044*10^22 molecules   [2*12.044*10^22*10-23]/6.022
                                             = 0.4 g H2

Then using Faradays law(here comes the doubtful part),
mH₂/mO₂                                =    EH₂/EO₂
o.4/mO2                                   =    [( 2/2)/(32/4)]
0.4/mO2                                    =        1/8
mO2  = 0.4 * 8 = 3.2 g.
Is this correct?I'm really worried about my E values values.hope I have substituted correctly?
Thank you.

[dufengtao]

What is the EH₂?

[leena]

What is the EH₂?

Sorry,
I meant E H₂ as the equivalent weight of Hydrogen gas.
hope that's what you meant to ask or is my value for E H₂ wrong?

[dufengtao]

hope that's what you meant to ask or is my value for E H₂ wrong?

I had realized the E H2 according to your explain, for the term of equivalent weight did not appear in the textbook of my country, that is to say, we do not use the equivalent weight to calculate something. to my knowlege, the result of the 3.2g O₂ is absolute right. the right answer my be (1) and (2), but  in my system of chemistry, we can do it wihtout the use the Faraday law. we do it as follows:
            2H₂O :rarrow:2H₂ + O₂
                                                   4                        32
                                                   0.4                      x
x=0.4g*32/4=3.2g

So we just need the Avogadro constant.

[dufengtao]

2H2O :rarrow:2H2 + O2
                      4      32
                     0.4     x
x=0.4g*32/4=3.2g

[dufengtao]

2H₂O :rarrow:2H₂ + O₂. This equation is the total reaction of the cell.

[leena]

Thank you sooo... much,dufengtao.I badly needed to know if my answer was correct.
Thanks again!