On the basis of the reactions observed in the six test tubes, explain why the position of hydrogen cannot be fixed exactly with respect to all of the other elements listed in the activity series.
Introduction
The activity series is a list of elements arranged in order of their reactivity. The more reactive an element is, the more likely it is to lose electrons and form cations. In an electrochemical cell, the more reactive element will be oxidized, and the less reactive element will be reduced.
Experiment
In this experiment, six test tubes were prepared containing the following substances:
- Test tube 1: 0.1 M hydrochloric acid (HCl) and a piece of magnesium metal
- Test tube 2: 0.1 M hydrochloric acid (HCl) and a piece of silver metal
- Test tube 3: 0.1 M hydrochloric acid (HCl) and a piece of lead metal
- Test tube 4: 0.1 M copper(II) sulfate (CuSO4) solution and a piece of magnesium metal
- Test tube 5: 0.1 M copper(II) sulfate (CuSO4) solution and a piece of silver metal
- Test tube 6: 0.1 M copper(II) sulfate (CuSO4) solution and a piece of lead metal
The test tubes were then observed for any signs of a reaction.
Results
The results of the experiment were as follows:
- Test tube 1: A vigorous reaction occurred, and hydrogen gas was produced.
- Test tube 2: No reaction occurred.
- Test tube 3: A slow reaction occurred, and hydrogen gas was produced.
- Test tube 4: A vigorous reaction occurred, and copper metal was deposited on the magnesium metal.
- Test tube 5: No reaction occurred.
- Test tube 6: No reaction occurred.
Discussion
The results of this experiment show that hydrogen is more reactive than silver and lead, but less reactive than copper. This is because hydrogen has a single electron in its valence shell, which it can easily lose to form a hydrogen ion (H+). Silver and lead, on the other hand, have more electrons in their valence shells, which are less easily lost. Copper has one electron in its valence shell, but it is more tightly bound than the electron in hydrogen.
The position of hydrogen in the activity series is therefore not fixed exactly with respect to all of the other elements listed in the activity series. It can be placed between silver and lead, but its exact position depends on the specific reaction being considered.
Additional questions
- What additional test(s) would be needed to establish the exact position of hydrogen in the activity series?
One additional test that could be performed is to react hydrogen with a solution of copper(II) sulfate. If hydrogen is more reactive than copper, then it will displace copper from the solution, forming copper metal. If hydrogen is less reactive than copper, then no reaction will occur.
Another additional test that could be performed is to react hydrogen with a solution of silver nitrate. If hydrogen is more reactive than silver, then it will displace silver from the solution, forming silver metal. If hydrogen is less reactive than silver, then no reaction will occur.
Conclusion
The position of hydrogen in the activity series is not fixed exactly with respect to all of the other elements listed in the activity series. It can be placed between silver and lead, but its exact position depends on the specific reaction being considered.
