Safari File E ile Edit View Bookmarks Help Wed 1:35 AMQ Progress Check 14 CHEM 1
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Safari File E ile Edit View Bookmarks Help Wed 1:35 AMQ Progress Check 14 CHEM 1212 FA 2015 +www.webassign.net ten Circuits 'narwy Store a Capacitor t strogen Rec. " Institu" ww-win When molten zinc(II) chloride (ZnCl2) is electrolyzed, zinc is deposited at the cathode. It electrolytic cell to form the deposit. Answer the questions that follow: is desired to deposit 10.62 grams of zinc. A current of 14.0 amperes is pessed through the A. What is the stoichiometric ratio for the number of moles of electrons to moles of sinc? 2 1| mole Zn 2| mole electrons B. How many moles of electrons need to pass in order to deposit this mass of zinc? E 0.325| moles electrons ? C. How long should you let the ament fowthrough the celOn mntes) norder to deposit this mass of 37.3 minutes Useful Information Zinc-65.410 g/mol Faraday constant " 9.648 534× 104 emolee' Practice Another VersionExplanation / Answer
when zinc metal is deposited at cathode , the half cell reaction is
Zn+2(aq) + 2e- -------> Zn(s)
Thus to deposit one mole of zinc metal 2 moles of electrons are required to pass through the cell.
According to first law of Faraday
w = E. i.t / 96500 or w/E = i.t /96500 where w= weight of substance discharged
E = equivalent weight of the substance discharged
i= current in amperes
t= time in sec.
We also know that [w/E] is the number of equivalents of substance discharged and this equals to the number of moles of electrons required to discharge that amount. [since one mole of electrons always deposit one equivalent mass of the substance discharged]
Thus w/E = 10.68x2 / 65.38 = 0.326 = number of moles of electrons [ one mole of zinc has two equivalents]
similarly time also calculated from the same formula as follows:
w /E = i.t /96500 = 0.326 = 14.0xt / 96500
Thus t= 2247.07 sec = 37.45 min
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