1. Questions

Chemistry

If a copper sample containing some zinc impurity is to be purified by electrolysis, the anode and the cathode must be which of the following?

a. anode: pure copper cathode: pure zinc
b. anode: pure zinc cathode: pure copper
c. anode: pure copper cathode: impure copper
d. anode: impure copper cathode: pure copper
e. anode: impure copper cathode: pure zinc

  1. 👍
  2. 👎
  3. 👁
John

  1. What do you think and why? Remember that the anode is where oxidation takes place and will be negative.

    1. 👍
    2. 👎
    DrBob222

  2. I think c and d can be eliminated because they only have all coppers. Zinc needs to be an anode or cathode. I think that e is correct, because there needs to be an impurity somewhere, but I am not sure.

    1. 👍
    2. 👎
    John

  4. I want to correct something I wrote. The first part is ok. The second part is not ok. In a voltaic cell, oxidation occurs at the anode and it is negative. But when I just re-read the question, it says that the impure copper is to be purified by electrolysis. In an electrolytic cell, the anode is + and the cathode is -.

    1. 👍
    2. 👎
    DrBob222

  5. You have a piece of copper metal, mostly copper but with a small amount of Zn in it, and you want to purify it so the copper is by itself and the Zn is not in it. The problem calls that the impure copper. Here is what we want to happen. We want the Cu/Zn in the impure copper/zinc rod or bar to go into solution as this.
    Cu ==> Cu+2 + 2 electrons
    Zn ==> Zn^2 + 2 electrons.
    So one electrode will be the impure piece of Cu/Zn we have been given.

    At the other electrode, we want the Cu^+2, now in solution form, to plate out. What will we plate it out on. A thin strip of copper metal (in the problem called pure copper), of course. And the electrolysis cell will have insufficient voltage to plate out the Zn^+2, now in solution, so it will stay in solution.
    That eliminates answers a, b, and e since we aren't trying to purify Zn. We want impure Cu/Zn to go into solution at one electrode and for the copper ions then in solutiion to plate out at the other electrode. If we want + charged Cu^+2 ions to plate out, they will be attracted to the negatively charged electrode of the cell, the cathode in an electrolytic cell; therefore, we place a thin strip of pure copper for the cathode. That means we place our impure Cu/Zn metal bar (or whatever shape it has) as the anode at the positvely charged electrode. That makes d the correct choice.

    1. 👍
    2. 👎
    DrBob222

  6. 2

    1. 👍
    2. 👎
    Anonymous

Respond to this Question

First Name

Your Response

Similar Questions

  1. Chemistry

    Given the density of copper 8.96g/mL, zinc 7.14g/mL, and brass 8.36g/mL. What is the fraction of copper and zinc in brass (expressed as %)? Please show me step by step how to calculate this. Thank you.

  2. chemistry

    pure zinc metal into a solution of copper(II) sulfate, the zinc will slowly dissolve to produce zinc sulfate solution, and the copper(II) ion of the copper(II) sulfate will be converted to metallic copper. Write the unbalanced

  3. chemistry

    Before 1982 the US Mint cast penny coins from a copper and zinc mixture. If a 1980 penny weighs 3.051g and contains 0.153g zinc, what is the percent of copper in the coins?

  4. Chemistry

    A voltaic cell operates with 0.40 M Zn 2+ at the solid zinc anode and 1.45 M Zn2+ at the solid zinc cathode at 25 C. Is the reaction thermodynamically favored?

  1. Honors Chemistry

    We did the gold penny lab, where we bathed a copper penny in a hot zinc-NaOH mixture to turn it a silver color, then we heated that in a flame to turn it a gold color. There are two questions that go with this lab that I don't

  2. CHEMISTRY

    Zinc is determined by precipitating and weighing as Zn2Fe(CN)6. a. What weight of zinc is contained in a sample that gives 0.348 g precipitate? b. What weight of precipitate would be formed from 0.500 g of Zinc?

  3. Chemistry ,Reactions at Electrodes during Electrol

    Reactions at Electrodes during Electrolysis Which half-reaction will take place at the cathode during the electrolysis of molten MgCl2? 2Cl- > Cl2 + 2e- Cl2 + 2e- > 2Cl- Mg2+ + 2e- > Mg Mg > Mg2+ + 2e- Which half-reaction will

  4. Chemistry

    1. Which of the following metals is oxidized by calcium ions? *potassium zinc iron lead 2. The first electrochemical cell was invented by ____. Michael Faraday *Alessandro Volta James Maxwell Benjamin Franklin 3. Why can't a lead

  1. general chemistry

    I need the oxidation half reactions, reduction half reactions, and net ionic equations for the following reactions: 1)magnesium +0.1M zinc sulfate 2)copper+0.1M zinc sulfate 3)zinc+0.1M copper(II)sulfate 4)zinc+3M HCl 5)copper+3M

  2. CHEMISTRY

    brass is a subtitutional alloy consisting of a solution of copper and zinc. a particulae sample of red brass consisting of 80% copper and 20% zinc by mass has a density of 8750kg/m^3. a. what is the molality of zinc in the solid

  3. chemistry

    Write the anodic reaction for the electrolysis of concentrated zinc chloride solution. (a) Using plantium electrodes. (b) Using zinc electrodes

  4. Chemistry

    Zinc has three major and two minor isotopes. For this problem, assume that the only isotopes of zinc are the major ones, zinc-64, zinc-66, and zinc-68. The atomic mass of zinc-64 is 63.9291 Da, that of zinc-66 is 65.9260 Da, and

You can view more similar questions or ask a new question.