Which one of the following is most reactive towards water?

Options

A. Sodium
B. Potassium
C. Calcium
D. Aluminium

Explanation

To determine which metal is most reactive towards water from the given options (sodium, potassium, calcium, and aluminum), we can follow these steps:

### Step 1: List the Metals
The metals given in the question are:
- Sodium (Na)
- Potassium (K)
- Calcium (Ca)
- Aluminum (Al)

### Step 2: Understand Reactivity with Water
Metals react with water to form hydroxides and hydrogen gas. The reactivity of metals with water generally increases down the group in the periodic table for alkali metals (like sodium and potassium) and alkaline earth metals (like calcium).

### Step 3: Refer to the Reactivity Series
The reactivity series of metals helps us understand their reactivity. In this series:
- Potassium (K) is more reactive than Sodium (Na).
- Sodium (Na) is more reactive than Calcium (Ca).
- Calcium (Ca) is more reactive than Aluminum (Al).

### Step 4: Analyze the Reactivity of Each Metal
- **Potassium (K)**: Highly reactive with water, producing potassium hydroxide and hydrogen gas. The reaction is very exothermic and can cause the hydrogen gas to ignite.
- **Sodium (Na)**: Also reactive with water, producing sodium hydroxide and hydrogen gas. The reaction is exothermic but less violent than potassium.
- **Calcium (Ca)**: Reacts with water to form calcium hydroxide and hydrogen gas, but the reaction is less vigorous compared to sodium and potassium.
- **Aluminum (Al)**: Does not react with water under normal conditions.

### Step 5: Determine the Most Reactive Metal
From the analysis, we can conclude:
- Potassium is the most reactive metal towards water among the options provided.

### Final Answer
**Potassium (K) is the most reactive towards water.**

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