The elements that reacts with cold water

Options

A. Mg
B. Ca
C. Be
D. Mg & Ca

Answer

To determine which elements react with cold water, we can analyze the behavior of the given elements: Magnesium (Mg), Calcium (Ca), and Phosphorus (P).

### Step-by-Step Solution:

1. **Identify the Elements**: The elements in question are Magnesium (Mg), Calcium (Ca), and Phosphorus (P).

2. **Understand the Reactivity of S-Block Elements**: The S-block elements (Group 1 and Group 2) are known for their reactivity with water. Among these, Group 1 elements (alkali metals) react vigorously with water, while Group 2 elements (alkaline earth metals) have varying reactivity.

3. **Reactivity of Magnesium (Mg)**:
- Magnesium does not react with cold water. It reacts with steam to form magnesium oxide and hydrogen gas.
- Reaction: \( \text{Mg} + \text{H}_2\text{O (steam)} \rightarrow \text{MgO} + \text{H}_2 \)

4. **Reactivity of Calcium (Ca)**:
- Calcium, being an alkaline earth metal, reacts with cold water.
- Reaction: \( \text{Ca} + 2\text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{H}_2 \)
- This reaction produces calcium hydroxide and hydrogen gas.

5. **Reactivity of Phosphorus (P)**:
- Phosphorus does not react with water under normal conditions. It is a non-metal and does not exhibit the same reactivity as metals.

6. **Conclusion**: Based on the reactivity of the elements with cold water, the only element that reacts with cold water is Calcium (Ca).

### Final Answer:
**Calcium (Ca)** is the element that reacts with cold water.

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