IB MYP Integrated Sciences e-Assessment : Reaction kinetics
Exam Style Practice Questions - New Syllabus
Question (4 marks)
The Statue of Liberty changed colour because the copper metal reacted with oxygen in the atmosphere in a process called corrosion. One of the methods used to prevent corrosion is electroplating. Electroplating is a process that involves coating a thin layer of metal on the surface of another metal using an electric current. This process is commonly used in industry to prevent corrosion or to cover a relatively cheap metal with a more expensive metal, such as silver, gold or zinc. You can see many electroplated objects around you, for example: silver-plated tableware, watches and rings.
The animation below shows how a copper coin can be electroplated.
There are several factors that could affect the mass of the electroplated metal on the coin, for example: current, voltage, concentration of solution, temperature, surface area of metal coin in solution and duration of electroplating.
A student wanted to investigate the electroplating process in her school laboratory. She wanted to coat a copper coin with nickel using a 10 g nickel bar as a source. She wanted to test how changing the current will affect the mass of nickel coating the copper coin. Her equipment is shown below:
There are many control variables in this experiment. For each of the control variables below, predict the effect on the mass of nickel coating the coin. Use scientific knowledge and understanding to justify your answer.
If the time of one trial was too short
Effect on mass
Justification
If the temperature of one trial was too high
Effect on mass
Justification
▶️Answer/Explanation
Ans:
If the time of one trial was too short:
- Effect on mass: The mass of nickel coating the coin would be lower than expected.
- Justification: Electroplating is a process that takes time. The longer the time, the more nickel ions from the solution will be reduced and deposited onto the copper coin. If the time is too short, fewer nickel ions will have the opportunity to transfer and adhere to the coin, resulting in a smaller mass deposit.
If the temperature of one trial was too high:
- Effect on mass: The mass of nickel coating the coin could be higher or lower depending on the specific temperature range and the solution’s properties. However, a slight increase is more likely.
- Justification: Increased Rate of Reaction: Generally, higher temperatures increase the rate of chemical reactions. In electroplating, this could mean a faster rate of nickel ion reduction and deposition onto the coin.