High School Chemistry : Help with Electrolytic Cells

Study concepts, example questions & explanations for High School Chemistry

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Example Questions

Example Question #1 : Electrochemistry

How does an electrolytic cell differ from a galvanic cell?

Possible Answers:

The cathode is marked negative in an electrolytic cell

The cell potential is positive in an electrolytic cell

Oxidation takes place at the anode in a galvanic cell, but at the cathode in an electrolytic cell

Oxidation takes place at the anode in an electrolytic cell, but at the cathode in a galvanic cell

Correct answer:

The cathode is marked negative in an electrolytic cell

Explanation:

Oxidation always takes place at the anode, regardless of the electrical cell type. The charges on the anode and cathode are reversed between galvanic and electrolytic cells. In electrolytic cells, the cathodes are marked negative and the anodes are marked positive. In galvanic cells, the reverse is true: cathodes are marked positive and anodes are marked negative.

Example Question #2 : Electrochemistry

Toward which pole do the electrons travel in an electrolytic cell?

Possible Answers:

Towards the anode

The electrons do not travel; only the protons travel

Towards the cathode

More information is needed

Towards the positive pole

Correct answer:

Towards the cathode

Explanation:

Reduction always occurs at the cathode, and oxidation always occurs at the anode. Since reduction is the addition of electrons, electrons must travel toward the site of reduction.

In an electrolytic cell the negative charge is on the cathode, while the positive charge is on the anode. Since an electrolytic cell requires energy to perpetuate the reaction, we are pushing the electrons against their potential gradient. The electrons, which are negatively charged, are traveling towards the cathode, which is also negatively charged.

Example Question #2 : Electrochemistry

       

          

The following reaction below takes place in an electrochemical cell:

Is the cell galvanic or voltaic?

Possible Answers:

Electrolytic

Both

Galvanic

Neither

Correct answer:

Galvanic

Explanation:

 

 

Since our overall reaction includes magnesium solid in the reactants, we must invert the first equation, including the sign of the electrical potential.

 

This cell is galvanic because the electrical potential, , is positive. Galvanic cells involve spontaneous reactions, and therefore, do not need any external energy source to drive the reaction.

Example Question #3 : Electrochemistry

 

 

The following reaction below takes place in an electrochemical cell:

Which of the following best describes this cell?

Possible Answers:

Both

Electrolytic

Neither

Galvanic 

Correct answer:

Electrolytic

Explanation:

 

 

Since our overall reaction includes calcium solid in the reactants, we must invert the second equation, including the sign of the electrical potential.

 

This cell is electrolytic because the electrical potential, , is negative. Electrolytic cells involve nonspontaneous reactions, and therefore, must have an external voltage source such as a battery to drive their reactions.

Example Question #4 : Electrochemistry

         

             

          

        

        

Which of the following species would mostly likely be oxidized, if placed in a electrochemical cell with another species?

Possible Answers:

Correct answer:

Explanation:

Using the equation: , for a spontaneous reaction to occur,  must be positive. With solid zinc as the reactant, any other solid can act as the product, and still give a positive . This is because, subtracting a negative number will give a positive value.

As a result, the equation,, will become inverted to make the solid zinc a reactant. . Solid zinc will give electrons, and oxidize, to reduce other ions. 

Example Question #5 : Electrochemistry

                  

         

For the following reaction to occur does the does the electrochemical cell voltaic or galvanic?

Possible Answers:

Neither 

Galvanic

Electrolytic

Both 

Correct answer:

Electrolytic

Explanation:

First we must rearrange the reduction potentials so that when added together, they match the reaction that takes place in the electrochemical cell.

                  

In the overall reaction,  is in the reactant side, so the  equation must be inverted.

       

Use the equation:  to find the 

 is product, while  is the reactant.

The cell must be electrolytic because the  value is negative. This means, this the reaction is a non-spontaneous reaction and need a applied energy source to make the reaction take place.

Example Question #6 : Electrochemistry

How does an electrolytic cell differ from a galvanic cell?

Possible Answers:

Oxidation takes place at the anode in an electrolytic cell, but at the cathode in a galvanic cell

Oxidation takes place at the anode in a galvanic cell, but at the cathode in an electrolytic cell

The cathode is marked negative in an electrolytic cell

The cell potential is positive in an electrolytic cell

Correct answer:

The cathode is marked negative in an electrolytic cell

Explanation:

Oxidation always takes place at the anode, regardless of the electrical cell type. The charges on the anode and cathode are reversed between galvanic and electrolytic cells. In electrolytic cells, the cathodes are marked negative and the anodes are marked positive. In galvanic cells, the reverse is true: cathodes are marked positive and anodes are marked negative.

Example Question #11 : Electrochemistry

How does an electrolytic cell differ from a galvanic cell?

Possible Answers:

Oxidation takes place at the anode in a galvanic cell, but at the cathode in an electrolytic cell

The cathode is marked negative in an electrolytic cell

Oxidation takes place at the anode in an electrolytic cell, but at the cathode in a galvanic cell

The cell potential is positive in an electrolytic cell

Correct answer:

The cathode is marked negative in an electrolytic cell

Explanation:

Oxidation always takes place at the anode, regardless of the electrical cell type. The charges on the anode and cathode are reversed between galvanic and electrolytic cells. In electrolytic cells, the cathodes are marked negative and the anodes are marked positive. In galvanic cells, the reverse is true: cathodes are marked positive and anodes are marked negative.

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