Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 18: Problem 97

Industrially, copper is purified by electrolysis. The impure copper acts as the anode, and the cathode is made of pure copper. The electrodes are immersed in a CuSO \(_{4}\) solution. During electrolysis, copper at the anode enters the solution as \(\mathrm{Cu}^{2+}\) while \(\mathrm{Cu}^{2+}\) ions are reduced at the cathode. (a) Write halfcell reactions and the overall reaction for the electrolytic process. (b) Suppose the anode was contaminated with \(\mathrm{Zn}\) and \(\mathrm{Ag} .\) Explain what happens to these impurities during electrolysis. (c) How many hours will it take to obtain \(1.00 \mathrm{~kg}\) of \(\mathrm{Cu}\) at a current of \(18.9 \mathrm{~A} ?\)

Short Answer

Expert verified
\[\begin{align*}& \text{(a)} \quad &\mathrm{Cu^{2+}(aq)+2e^{-}\rightarrow Cu(s)} \& &\mathrm{Cu(s)\rightarrow Cu^{2+}(aq)+2e^{-}} \& &\mathrm{Cu(s) + Cu^{2+}(aq) \rightarrow Cu^{2+}(aq) + Cu(s)} \& \text{(b)} \quad &\text{Silver will not react and fall to the bottom of the cell, while zinc will dissolve.} \& \text{(c)} \quad &\text{Use Faraday's formula to find the time, applying the given values.}\end{align*}\]

Step by step solution

01

Writing Halfcell and Overall Reactions

In the CuSO4 electrolyte solution, the Cu^2+ ions are reduced at the cathode, giving us a half-reaction of: \[\mathrm{Cu^{2+}(aq)+2e^{-}\rightarrow Cu(s)}\]At the anode (impure copper), copper atoms are oxidized to copper ions, and we can write:\[\mathrm{Cu(s)\rightarrow Cu^{2+}(aq)+2e^{-}}\]Adding these two half-cell reactions yields the overall reaction for the electrolytic process, which is:\[\mathrm{Cu(s) + Cu^{2+}(aq) \rightarrow Cu^{2+}(aq) + Cu(s)}\]
02

Behavior of Zn and Ag during Electrolysis

During electrolysis, 'nobler' metals like silver (Ag) would remain unreacted and would fall to the bottom of the electrochemical cell. In contrast, metals more 'reactive' than copper, such as zinc (Zn), would dissolve into the solution along with copper.
03

Calculation of Electrolysis Time

We use Faraday’s laws of electrolysis, in which the mass of substance deposited is directly proportional to the quantity of electricity. The molar mass of copper, \(M_{\mathrm{Cu}}\), is 63.55 g/mol. The Faraday constant, \(F\), is 96485 C/mol. Therefore, to deposit 1kg (or 1000 g) of copper, the total charge needed (\(Q\)) is:\[Q=\frac{1000 \, \mathrm{g}}{63.55 \, \mathrm{g/mol}} \times 2 \, \mathrm{F}\]Then, the time (\(t\)) required (at a current (\(I\)) of 18.9 A), can be calculated using:\[t=\frac{Q}{I}\]

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

In the electrolysis of an aqueous AgNO \(_{3}\) solution, \(0.67 \mathrm{~g}\) of \(\mathrm{Ag}\) is deposited after a certain period of time. (a) Write the half- reaction for the reduction of \(\mathrm{Ag}^{+} .\) (b) What is the probable oxidation halfreaction? (c) Calculate the quantity of electricity used, in coulombs.

Which species in each pair is a better reducing agent under standard-state conditions: (a) Na or Li? (b) \(\mathrm{H}_{2}\) or \(\mathrm{I}_{2} ?(\mathrm{c}) \mathrm{Fe}^{2+}\) or \(\mathrm{Ag} ?\) (d) \(\mathrm{Br}^{-}\) or \(\mathrm{Co}^{2+} ?\)

Gold will not dissolve in either concentrated nitric acid or concentrated hydrochloric acid. However, the metal does dissolve in a mixture of the acids (one part \(\mathrm{HNO}_{3}\) and three parts \(\mathrm{HCl}\) by volume \()\) called aqua regia. (a) Write a balanced equation for this reaction. (Hint: Among the products are \(\mathrm{HAuCl}_{4}\) and \(\mathrm{NO}_{2} .\) ) (b) What is the function of \(\mathrm{HCl} ?\)

A constant electric current flows for \(3.75 \mathrm{~h}\) through two electrolytic cells connected in series. One contains a solution of \(\mathrm{AgNO}_{3}\) and the second a solution of \(\mathrm{CuCl}_{2}\). During this time \(2.00 \mathrm{~g}\) of silver are deposited in the first cell. (a) How many grams of copper are deposited in the second cell? (b) What is the current flowing, in amperes?

Consider the electrolysis of molten barium chloride, \(\mathrm{BaCl}_{2}\). (a) Write the half-reactions. (b) How many grams of barium metal can be produced by supplying 0.50 A for 30 min?
See all solutions

Recommended explanations on Chemistry Textbooks

Ionic and Molecular Compounds

Read Explanation

The Earths Atmosphere

Read Explanation

Inorganic Chemistry

Read Explanation

Chemistry Branches

Read Explanation

Kinetics

Read Explanation

Organic Chemistry

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free