Explanation:

The reaction of alkali metals with water is highly exothermic and produces hydrogen gas and metal hydroxide. The reactivity of alkali metals with water increases from lithium to cesium. However, the reactivity of sodium is higher than lithium, even though lithium has a more negative E0 value. This can be explained by the following reasons:

Hydration Energy:

- As we move down the group, the size of the alkali metal ion increases, and the hydration energy decreases. Hydration energy is the energy released when an ion is surrounded by water molecules.
- Lithium ion is small in size, and its hydration energy is high. This makes it difficult for water molecules to approach the lithium ion and initiate the reaction.
- Sodium ion is larger in size than lithium ion, and its hydration energy is lower. This makes it easier for water molecules to approach the sodium ion and initiate the reaction.

High Hydration Energy of Lithium:

- Lithium has a high hydration energy due to its small size and high charge density. It attracts water molecules strongly and forms a stable hydration shell around it.
- This stable hydration shell around lithium ion makes it difficult for water molecules to approach and react with it. Hence, the reaction of lithium with water is less vigorous.

Small Size of Sodium:

- Sodium ion is larger in size than lithium ion. This means that the distance between the sodium ion and the oxygen atoms in water molecules is larger.
- This larger distance weakens the bond between the oxygen atoms and the hydrogen atoms in water molecules. Hence, sodium ion can easily break the bonds between the oxygen and hydrogen atoms, and initiate the reaction with water.

Proton Donor:

- Lithium ion is a proton donor and can react with water to form lithium hydroxide and hydrogen gas. However, the reaction is slow and less vigorous due to the high hydration energy of lithium ion.
- Sodium ion is also a proton donor and can react with water to form sodium hydroxide and hydrogen gas. The reaction is more vigorous than lithium due to the lower hydration energy of sodium ion.

Conclusion:

The reason for the less vigorous reaction of lithium with water compared to sodium is due to the high hydration energy of lithium, which makes it difficult for water molecules to approach and react with it. Sodium, on the other hand, has lower hydration energy and a larger size, which makes it easier for water molecules to approach and initiate the reaction.