The dissociation constant of monobasic acids `A, B,C` and `D` are `6 xx 10^(-4),5xx10^(-5), 3.6 xx 10^(-6)`, and `7 xx 10^(-10)`, respectively. The `pH` values of their `0.1M` aqueous solutions are in the order.

Options

A. `D gt C gt B gt A`
B. `A gt B gt C gt D`
C. `A =B = C = D`
D. None

Explanation

To determine the order of pH values for the given monobasic acids A, B, C, and D based on their dissociation constants, we can follow these steps:

### Step 1: Identify the dissociation constants
The dissociation constants (Ka) for the acids are:
- Acid A: \( K_a = 6 \times 10^{-4} \)
- Acid B: \( K_a = 5 \times 10^{-5} \)
- Acid C: \( K_a = 3.6 \times 10^{-6} \)
- Acid D: \( K_a = 7 \times 10^{-10} \)

### Step 2: Understand the relationship between dissociation constant and pH
The dissociation constant (Ka) indicates how well an acid dissociates in solution. A higher Ka value means the acid dissociates more, producing more hydrogen ions (H⁺) in solution, which leads to a lower pH. Conversely, a lower Ka means fewer H⁺ ions and a higher pH.

### Step 3: Rank the acids based on their dissociation constants
From the given values, we can rank the acids in order of their dissociation constants:
1. Acid A: \( 6 \times 10^{-4} \) (highest)
2. Acid B: \( 5 \times 10^{-5} \)
3. Acid C: \( 3.6 \times 10^{-6} \)
4. Acid D: \( 7 \times 10^{-10} \) (lowest)

### Step 4: Determine the order of pH values
Since a higher dissociation constant corresponds to a lower pH, we can arrange the acids in order of increasing pH:
- Acid A (lowest pH)
- Acid B
- Acid C
- Acid D (highest pH)

Thus, the order of pH values from lowest to highest is:
**A < B < C < D**

### Final Answer
The pH values of their 0.1M aqueous solutions are in the order: **A < B < C < D**.

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