Which pair of substances gives same gaseous product, when these react with water

Options

A. Ca and `CaH_(2)`
B. Na and `Na_(2)O_(2)`
C. K and `KO_(2)`
D. Ba and `BaO_(2)`

Explanation

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

### Step 1: Analyze the first option - Calcium (Ca)
- When calcium reacts with water, the reaction can be represented as:
\[ \text{Ca} + 2\text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{H}_2 \uparrow \]
- The gaseous product formed is hydrogen gas (H₂).

### Step 2: Analyze the second option - Sodium (Na)
- When sodium reacts with water, the reaction is:
\[ \text{2Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2 \uparrow \]
- The gaseous product formed is also hydrogen gas (H₂).

### Step 3: Analyze the third option - Potassium (K)
- When potassium reacts with water, the reaction is:
\[ \text{2K} + 2\text{H}_2\text{O} \rightarrow 2\text{KOH} + \text{H}_2 \uparrow \]
- The gaseous product formed is again hydrogen gas (H₂).

### Step 4: Analyze the fourth option - Barium (Ba)
- When barium reacts with water, the reaction is:
\[ \text{Ba} + 2\text{H}_2\text{O} \rightarrow \text{Ba(OH)}_2 + \text{H}_2 \uparrow \]
- The gaseous product formed is also hydrogen gas (H₂).

### Step 5: Analyze the fifth option - Sodium Peroxide (Na₂O₂)
- When sodium peroxide reacts with water, the reaction is:
\[ \text{Na}_2\text{O}_2 + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2\text{O}_2 \]
- This reaction does not produce hydrogen gas but rather hydrogen peroxide (H₂O₂) as a product.

### Conclusion:
From the analysis, we can see that both calcium (Ca) and sodium (Na) produce hydrogen gas (H₂) when they react with water. Therefore, the pair of substances that gives the same gaseous product when they react with water is:

**Calcium (Ca) and Sodium (Na)**.