Which of the following is correct ?
(i) Lithium is better reducing agent than sodium
(ii) Sodium is better reducing agent than potassium
(iii) Rubidium is better reducing agent than sodium
(iv) The Rubidium is better reducing agent than lithium

Options

A. all are correct
B. I,ii & iv only
C. I,iii & iv only
D. I,ii & iii only

Answer

To determine which of the given statements about the reducing agents among alkali metals is correct, we need to analyze the reducing character of these metals based on their properties.

### Step-by-Step Solution:

1. **Understanding Reducing Agents**:
A reducing agent is a substance that donates electrons to another substance, thereby reducing it while itself getting oxidized. The strength of a reducing agent is often correlated with its ability to lose electrons easily.

2. **Trends in Group 1 Alkali Metals**:
- The alkali metals in Group 1 of the periodic table include Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), and Cesium (Cs).
- As we move down the group from Lithium to Cesium, the atomic size increases. This increase in size generally leads to a greater tendency to lose electrons, thus increasing the reducing character.

3. **Evaluating Each Statement**:
- **Statement (i)**: "Lithium is a better reducing agent than sodium."
- This statement is **correct**. Despite Lithium having a higher ionization energy, its very negative standard reduction potential (E° = -3.04 V) makes it a stronger reducing agent than Sodium.

- **Statement (ii)**: "Sodium is a better reducing agent than potassium."
- This statement is **incorrect**. Potassium is a better reducing agent than Sodium because it is lower in the group and has a larger atomic size, making it easier to lose electrons.

- **Statement (iii)**: "Rubidium is a better reducing agent than sodium."
- This statement is **correct**. Rubidium, being lower in the group than Sodium, has a greater tendency to lose electrons and is thus a better reducing agent.

- **Statement (iv)**: "Rubidium is a better reducing agent than lithium."
- This statement is **correct**. Rubidium is larger than Lithium, making it easier to lose electrons, thus it is a better reducing agent.

4. **Conclusion**:
Based on the analysis, the correct statements are (i), (iii), and (iv). Therefore, the answer is that statements (i), (iii), and (iv) are correct.

### Final Answer:
The correct statements are:
- (i) Lithium is better reducing agent than sodium.
- (iii) Rubidium is better reducing agent than sodium.
- (iv) Rubidium is better reducing agent than lithium.