(a) Write the possible oxidation and reduction half-reactions that occur when magnesium is immersed in each of the following solutions: (i) HCl, (ii) an HCl solution containing dissolved oxygen, and (iii) an HCl solution containing dissolved oxygen and \(\mathrm{Fe}^{2+}\) ions. (b) In which of these solutions would you expect the magnesium to oxidize most rapidly? Why?

Short Answer

Expert verified
Answer: The fastest oxidizing solution for magnesium is the HCl solution containing both dissolved oxygen and \(\mathrm{Fe}^{2+}\) ions due to the increased number of electron-accepting species with higher reduction potentials, resulting in faster oxidation of magnesium.

Step by step solution

01

Part (a): Half-reactions in HCl solution

In HCl solution, magnesium undergoes oxidation (loses electrons), reacting with hydrogen ions (H+) from the HCl to form magnesium ions (Mg2+) and hydrogen gas (H2). The reactions are as follows: Oxidation half-reaction: \(\mathrm{Mg}(s) \rightarrow \mathrm{Mg}^{2+}(aq) + 2\mathrm{e}^{-}\) Reduction half-reaction: \(2\mathrm{H}^{+}(aq) + 2\mathrm{e}^{-} \rightarrow \mathrm{H}_{2}(g)\)
02

Part (a): Half-reactions in HCl solution with dissolved oxygen

In an HCl solution that contains dissolved oxygen, magnesium can still undergo the same oxidation reaction as above. Additionally, oxygen in the solution can accept electrons and react with water to form hydroxide ions (OH-). The reactions are as follows: Oxidation half-reaction: \(\mathrm{Mg}(s) \rightarrow \mathrm{Mg}^{2+}(aq) + 2\mathrm{e}^{-}\) Reduction half-reaction 1: \(2\mathrm{H}^{+}(aq) + 2\mathrm{e}^{-} \rightarrow \mathrm{H}_{2}(g)\) Reduction half-reaction 2: \(\mathrm{O}_{2}(g) + 2\mathrm{H}_{2}\mathrm{O}(l) + 4\mathrm{e}^{-} \rightarrow 4\mathrm{OH}^{-}(aq)\)
03

Part (a): Half-reactions in HCl solution with dissolved oxygen and \(\mathrm{Fe}^{2+}\) ions

In this solution, besides the above oxidation and reduction half-reactions, \(\mathrm{Fe}^{2+}\) ions can also accept electrons to form metallic iron (Fe). The reactions are as follows: Oxidation half-reaction: \(\mathrm{Mg}(s) \rightarrow \mathrm{Mg}^{2+}(aq) + 2\mathrm{e}^{-}\) Reduction half-reaction 1: \(2\mathrm{H}^{+}(aq) + 2\mathrm{e}^{-} \rightarrow \mathrm{H}_{2}(g)\) Reduction half-reaction 2: \(\mathrm{O}_{2}(g) + 2\mathrm{H}_{2}\mathrm{O}(l) + 4\mathrm{e}^{-} \rightarrow 4\mathrm{OH}^{-}(aq)\) Reduction half-reaction 3: \(\mathrm{Fe}^{2+}(aq) + 2\mathrm{e}^{-} \rightarrow \mathrm{Fe}(s)\)
04

Part (b): Identify the solution with the most rapid oxidation

Magnesium oxidizes most rapidly in the HCl solution containing both dissolved oxygen and \(\mathrm{Fe}^{2+}\) ions. The reason for this is the increased number of chemical species that can accept electrons, leading to faster oxidation of magnesium. In the HCl solution containing both dissolved oxygen and \(\mathrm{Fe}^{2+}\) ions, magnesium will primarily react with the dissolved oxygen and \(\mathrm{Fe}^{2+}\) ions, which have a higher reduction potential than H+ ions. This results in a faster overall reaction rate, leading to more rapid oxidation of magnesium.

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.

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

See all solutions

Recommended explanations on Physics Textbooks

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