The correct relationship between the `pH` of isomolar solutions of sodium oxide `(pH_(1))`, sodium sulphide `(pH_(2))`, sodium selenide `(pH_(3))` and sodium telluride `(pH_(4))` is

Options

A. `pH_(1) lt pH_(2) lt pH_(3) lt pH_(4)`
B. `pH_(1) gt pH_(2) gt pH_(3) gt pH_(4)`
C. `pH_(1) lt pH_(2) lt pH_(3) ~~pH_(4)`
D. `pH_(1) gt pH_(2)~~ pH_(3) lt pH_(4)`

Answer

To solve the problem regarding the relationship between the pH of isomolar solutions of sodium oxide (Na2O), sodium sulphide (Na2S), sodium selenide (Na2Se), and sodium telluride (Na2Te), we can follow these steps:

### Step 1: Understand the Reactions
Each sodium compound reacts with water to form a strong base (NaOH) and an acid:
- **Sodium oxide (Na2O)**:
\[ \text{Na}_2\text{O} + \text{H}_2\text{O} \rightarrow 2 \text{NaOH} \]
- **Sodium sulphide (Na2S)**:
\[ \text{Na}_2\text{S} + \text{H}_2\text{O} \rightarrow 2 \text{NaOH} + \text{H}_2\text{S} \]
- **Sodium selenide (Na2Se)**:
\[ \text{Na}_2\text{Se} + 2 \text{H}_2\text{O} \rightarrow 2 \text{NaOH} + \text{H}_2\text{Se} \]
- **Sodium telluride (Na2Te)**:
\[ \text{Na}_2\text{Te} + 2 \text{H}_2\text{O} \rightarrow 2 \text{NaOH} + \text{H}_2\text{Te} \]

### Step 2: Identify the Acidity of the Products
The acids formed from these reactions (H2O, H2S, H2Se, H2Te) can be ranked in terms of acidity:
- H2Te > H2Se > H2S > H2O

This ranking indicates that H2Te is the strongest acid and H2O is the weakest.

### Step 3: Analyze the pH Relationship
Since NaOH is a strong base, the pH of the solutions will be influenced by the strength of the acids formed:
- **For Na2Te**: The strongest acid (H2Te) will lead to a lower pH (more acidic).
- **For Na2Se**: A less strong acid (H2Se) will lead to a higher pH than Na2Te.
- **For Na2S**: An even weaker acid (H2S) will lead to a higher pH than Na2Se.
- **For Na2O**: The weakest acid (H2O) will lead to the highest pH.

### Step 4: Establish the pH Relationship
From the analysis:
- pH of Na2O (pH1) > pH of Na2S (pH2) > pH of Na2Se (pH3) > pH of Na2Te (pH4)

### Final Conclusion
The correct relationship between the pH values of the isomolar solutions is:
\[ \text{pH}_1 > \text{pH}_2 > \text{pH}_3 > \text{pH}_4 \]