A student carries out the electrolysis of a 1.0 M solution of sodium chloride using graphite electrodes. The setup for this experiment is shown below. 1.0 M NaCl(aq) --- a. Write an equation for the half reaction that occurs at the cathode. --- b. Two different gases are produced at the anode. Write equations for the two half reactions that result in the formation of these two gases. i. Equation for half reaction that produces gas 1 --- ii. Equation for half reaction that produces gas 2 --- c. Using the same current and electrodes, the student carries out a second electrolysis, this time of a saturated solution (approximately 6 M) of sodium chloride instead of a 1.0 M solution. What difference, if any, would you expect in the product or products formed at the i. cathode? --- ii. anode? --- Total 5 marks

SSCE VCE Chemistry Redox Reactions: A student carries out the electr

A student carries out the electrolysis of a 1.0 M solution of sodium chloride using graphite electrodes - VCE - SSCE Chemistry - Question 5 - 2004 - Paper 1

Question 5

A student carries out the electrolysis of a 1.0 M solution of sodium chloride using graphite electrodes. The setup for this experiment is shown below. 1.0 M NaCl(aq... show full transcript

Worked Solution & Example Answer:A student carries out the electrolysis of a 1.0 M solution of sodium chloride using graphite electrodes - VCE - SSCE Chemistry - Question 5 - 2004 - Paper 1

Step 1

Write an equation for the half reaction that occurs at the cathode.

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Answer

In the electrolysis of sodium chloride (NaCl), the reduction reaction that occurs at the cathode involves the reduction of water (H₂O) to produce hydrogen gas (H₂) and hydroxide ions (OH⁻). The half-reaction can be represented as:

$2H_2O + 2e^- \rightarrow H_2 + 2OH^-$

Step 2

Equation for half reaction that produces gas 1

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Answer

At the anode, the oxidation of chloride ions (Cl⁻) occurs, producing chlorine gas (Cl₂). The half-reaction can be represented as:

$2Cl^- \rightarrow Cl_2 + 2e^-$

Step 3

Equation for half reaction that produces gas 2

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Answer

Additionally, the oxidation of water (H₂O) can produce oxygen gas (O₂) at higher potentials. The half-reaction is:

$2H_2O \rightarrow O_2 + 4e^- + 4H^+$

Step 4

Using the same current and electrodes, what difference would you expect in the product or products formed at the cathode?

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Answer

In the case of a saturated solution (approximately 6 M) of sodium chloride, the increased concentration of Na⁺ ions could lead to the discharge of sodium ions instead of water. However, the more favorable reaction is typically the reduction of water, so you may still primarily form hydrogen gas:

$2H_2O + 2e^- \rightarrow H_2 + 2OH^-$

Step 5

What difference would you expect in the product or products formed at the anode?

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Answer

The increased concentration in a saturated solution will not change the primary reactions occurring at the anode. Chlorine gas (Cl₂) will still be produced from the oxidation of chloride ions, and oxygen may still form from water oxidation, but the predominant reaction remains the discharge of chloride ions:

$2Cl^- \rightarrow Cl_2 + 2e^-$

A student carries out the electrolysis of a 1.0 M solution of sodium chloride using graphite electrodes - VCE - SSCE Chemistry - Question 5 - 2004 - Paper 1

Worked Solution & Example Answer:A student carries out the electrolysis of a 1.0 M solution of sodium chloride using graphite electrodes - VCE - SSCE Chemistry - Question 5 - 2004 - Paper 1

Write an equation for the half reaction that occurs at the cathode.

Equation for half reaction that produces gas 1

Equation for half reaction that produces gas 2

Using the same current and electrodes, what difference would you expect in the product or products formed at the cathode?

What difference would you expect in the product or products formed at the anode?

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