Clean small pieces of magnesium, zinc, aluminium, iron and copper by rubbing them with a piece of sand paper. Take them in separate test tubes. Add about 10 mL of dilute hydrochloric acid to each of them.

Identify the correct statements (S).

1) The rate of evolution of hydrogen gas bubbles is not same in all the test tubes.

2) The rate of formation of bubbles is the fastest in the case of magnesium.

3) The reactivity decreases in the order : $Mg>Zn>Al>Fe>Cu$.

4) In the case of copper, no bubbles are seen and the temperature also remains unchanged. This shows that copper does not react with dilute HCl.

In this experiment, small pieces of magnesium, zinc, aluminum, iron, and copper are individually treated with dilute hydrochloric acid (HCl) in separate test tubes. Observing the rate of hydrogen gas bubble evolution in each case provides insight into the relative reactivity of these metals.

Given Statements:

1. The rate of evolution of hydrogen gas bubbles is not the same in all the test tubes.
2. The rate of bubble formation is the fastest in the case of magnesium.
3. The reactivity decreases in the order: Mg > Zn > Al > Fe > Cu.
4. In the case of copper, no bubbles are seen, and the temperature also remains unchanged, indicating copper does not react with dilute HCl.

Analysis and Correct Answer:

All statements are correct, except for statement 3, which inaccurately describes the reactivity order. The correct order of reactivity among these metals with dilute hydrochloric acid is:

Mg > Al > Zn > Fe > Cu.

This is because aluminum is more reactive than zinc when reacting with dilute acids. Therefore, in statement 3, zinc should not be placed ahead of aluminum in terms of reactivity.

Explanation of Each Statement:

• Statement 1: True, as different metals have varying reactivity levels with dilute hydrochloric acid, resulting in different rates of hydrogen gas evolution.
• Statement 2: True, magnesium is highly reactive with dilute HCl, causing the fastest formation of hydrogen bubbles.
• Statement 3: Incorrect, because the correct order is Mg > Al > Zn > Fe > Cu.
• Statement 4: True, as copper does not react with dilute hydrochloric acid, no hydrogen bubbles are produced, and the temperature remains unchanged.

In summary, only statement 3 is incorrect due to the misplacement of zinc and aluminum in the reactivity series.