ELC_Electrochemistry Lesson

Electrochemistry

Do you remember learning about oxidation-reduction (redox) reactions in the chemical reactions module? These are reactions that involve the transfer of electrons from one substance to another. Some redox reactions are spontaneous and some are not. Spontaneous redox reactions can be manipulated to produce electricity. In reverse, non-spontaneous reactions can be forced to occur by using electricity. The study of these reactions that involve electricity is referred to as electrochemistry. 

Oxidation-Reduction Reactions

Recall that oxidation  is the increase in oxidation number. Or, you can think of it as the loss of electrons. Reduction is the decrease in oxidation number, or the gain of electrons. You already learned how to assign oxidation numbers. This information was previously covered in the chemical reactions module. Now let's learn how to balance redox reactions.

Watch this video to learn how to balance a redox reaction.

Chart of Redox Oxidizers with Common Oxidizing Agents and products formed

Table for common oxidzers

Chart of Redox Reducers with Common Oxidizing Agents and products formed

Table for reduction rxns

Watch this video below where you will try these steps on your own. Then each step is reviewed in case you need help. Make sure to pause the video when indicated and try it on your own!

Often redox reactions take place in either acidic or basic solutions. These require a few more steps to balance. Watch the video below to learn how to balance a redox reaction in acid.

Now, watch the video below to learn how to balance a redox reaction in base. Make sure to participate along with the video!

You will need to be able to do stoichiometry involving redox reactions just as you do with other reactions.   Look at the example below.

Example In an acidic solution, HSO ion reacts with CIO3 ion to give SO42 ion and CI+ ion. a) Write a balanced net ionic equation for the reaction. You learned how to do this above! Try it on your own before you peek at the answer. 3HSO3 + CIO→ 3SO2 + 3H + CH b) How many milliliters of 0.150 M NaCIO3 solution are needed to react completely with 30.0 mL of 0.450 M NaHSO, solution? Remember that M is molarity and can be used as a conversion fact. 0.150 mol NaCIO3 = 1 L NACIO3 0.450 mol NaHSO3 = 1 L NaHSO3 # mL NaCIO, = (30.0 mL NaHSO₁/1000 mL NaHSO)(1 mol HSO/1 mol NaHSO)x(1 mol CIO/3 mol HSO)(1000 mL NACIO/0.150 mol NaClO)= 30.0 mL NaClO Notice that we didn't stop during the stoichiometry problem above. Just solve in one long problem.

If you need a review of solution stoichiometry, go to pages 10 and 11 in the chemical reactions module.  

Remember to work on the module practice problems as you complete each section of content.  

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