Which of the following pair of substance give same gaseous product on reaciton with water?

Options

A. `Ca and CaH_(2)`
B. `MgCO_(3)`
C. `Mg(NO_(3))_(2)`
D. `Ca(NO_(3))_(2)`

Explanation

To determine which pair of substances gives the same gaseous product when reacted with water, we can analyze the reactions of each substance with water step by step.

### Step-by-Step Solution:

1. **Identify the Substances**: We are given two substances, which are Calcium (Ca) and Calcium Hydride (CaH2).

2. **Reaction of Calcium with Water**:
- The reaction of Calcium (Ca) with water (H2O) can be represented as:
\[ \text{Ca} + 2 \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{H}_2 \]
- Here, Calcium reacts with water to form Calcium Hydroxide (Ca(OH)2) and Hydrogen gas (H2).

3. **Reaction of Calcium Hydride with Water**:
- The reaction of Calcium Hydride (CaH2) with water can be represented as:
\[ \text{CaH}_2 + 2 \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + 2 \text{H}_2 \]
- In this case, Calcium Hydride also reacts with water to form Calcium Hydroxide (Ca(OH)2) and Hydrogen gas (H2).

4. **Comparison of Products**:
- From both reactions, we observe that the gaseous product produced is Hydrogen (H2) in both cases.
- Therefore, both Calcium and Calcium Hydride give the same gaseous product when they react with water.

5. **Conclusion**:
- The pair of substances that gives the same gaseous product on reaction with water is Calcium (Ca) and Calcium Hydride (CaH2).

### Final Answer:
The correct option is **A: Calcium (Ca) and Calcium Hydride (CaH2)**.

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