Q. If same quantity of electricity is passed through three electrolytic cells containing FeSO4, Fe2(SO4)3 and Fe(NO3)3, then
A) The amounts of iron deposited in FeSO4 and Fe2(SO4)3, are equal.
B) The amounts of iron in FeSO4 is 1.5 times of the amt. of iron deposited in Fe(NO3)3.
C) The amounts of iron deposited in Fe2(SO4)3 and Fe(NO3)3 are equal.
D) The same amount of gas is evolved in all the three cases at the anode.
It is again a more than one correct ques.
I got the answer as BC.
But my friends are saying for D also.
What do you say? Please reply soon
Hi Ankul,
sorry to say,but i think the question is incomplete!! it must be clearly specified if we are using aqueous solution of these samples or molten ones! if we use aqueous samples then the ans will only be d,for in that case iron will not be deposited whether we use inert platinum electrodes or active iron electrodes as H+ will get preference and it wil get discharged to release equal amount of hydrogen gas!!!!!! but if the sample used is molten ones then the ans will b B,C on;y as the gases evolved will b different , therefore their equivalent masses will b different so the amounts released will obviously b different!! but if the samples are molten what gas will b released in case of the sulphates....any idea????? plzz post ur comments and sujjestions on my thoughts!!! kvs
well kvs i also thought on the same line as u. Since there was no mention of water in the electrolytic cell.. so i took them molten and got BC. It must be right.
Well, i think the gas evolved in case of sulphate should be SO2, but not sure of. What do u say???
Well, i think the gas evolved in case of sulphate should be SO2, but not sure of. What do u say???
Hi Ankul,
have you ever seen a question in which sulphates got discharged to give sulphurdioxide.....i have never seen any such reactions...........even in inorganic chemistry i have seen sulphites release sulphurdioxide but i have never done a reaction in which sulphates released sulphurdioxide...i think the same must apply here and so sulphurdioxide cannot be released.....in that case what gas will be evolved? God knows............but i will try to confirm....what are your thougts on what i have said?kvs
Well kvs, if sulphites can release SO2, then it might be that Sulphate would release SO3. And if that's not possible, then i dont see the possibility of any other gas being released by SO42-. Then it might be aqueous soln. and may be just D) would be correct. What do u say???
Hey Kvs, dont you think so that by changing the conc. of the salts, the reduction potential of Fe2+ or Fe3+ can be made greater than that of H+ and thus carry out its reduction instead of H+. And in that case, O2 will be the only gas evolved.
What do you say?? Please ignore my last reply in which I mention evolution of SO3, because SO42- cannot be oxidised, S is in its highest oxidation state.
What do you say?? Please ignore my last reply in which I mention evolution of SO3, because SO42- cannot be oxidised, S is in its highest oxidation state.
Hi ankul,
though what u say seems to be theoritically valid........it cant b practical.....if what u said is true there wud hav been no electrochemical series for all the redn and oxdn potentials will then depend on the concentration of the respective ions.......moreover if what u said were to b true then we wud hav been checking in each qn of electrochemistry we do,which of the ions will b liberated by calculating the redn potentials each time....we never do that. for example if the are sulphate and hydroxide ions(even when their concentrations are different) we say hydroxide will b liberated without calculating any redn potentials.........any ways if we were to start doing that i wud not attempt any qn of electrochemistry for the calculations wud b tooo lengthy!!!! What say???:-D(sorry i do not know any exact reason why ur thought is wrong) kvs
Well what u r saying also seems to be correct to me. But then i what shall we take it: molten or aq. soln. Couz, if taken molten, then what will be the gas evolved, and if taken aq., then the ques. seems to be a lill odd as there would be no participation of the salts in the ques. then. Just H2 and O2 will be evolved. What say????
Hey Kvs... Can u also give some suggestions for my Phenol ques. that i have posted in the same forum......