The solubility products of `MA, MB, MC` and MD are `1.8xx10^(-10), 4xx10^(-3), 4xx10^(-8)` and `6xx10^(-5)` respectively. If a `0.01M` solution of MX is added dropwise to a mixture containing `A^(-), B^(-), C^(-)` and `D^(-)` ions, then the one to be precipitated first will be:

Options

A. `MA`
B. `MB`
C. `MC`
D. `MD`

Explanation

To solve the problem, we need to determine which salt (MA, MB, MC, or MD) will precipitate first when a 0.01 M solution of MX is added to a mixture containing A^(-), B^(-), C^(-), and D^(-) ions. We will use the solubility product (Ksp) values provided for each salt to find out which anion will reach its precipitation point first.

### Step-by-Step Solution:

1. **Identify the Ksp Values**:
- For MA: Ksp = 1.8 x 10^(-10)
- For MB: Ksp = 4 x 10^(-3)
- For MC: Ksp = 4 x 10^(-8)
- For MD: Ksp = 6 x 10^(-5)

2. **Write the Expression for Ionic Product (IP)**:
The ionic product (IP) for each salt can be expressed as:
\[ IP = [M^+] \times [A^-] \quad \text{for MA} \]
\[ IP = [M^+] \times [B^-] \quad \text{for MB} \]
\[ IP = [M^+] \times [C^-] \quad \text{for MC} \]
\[ IP = [M^+] \times [D^-] \quad \text{for MD} \]
Where [M^+] is the concentration of MX added, which is 0.01 M.

3. **Calculate the Required Anion Concentration for Precipitation**:
To find the concentration of each anion required to start precipitation, we rearrange the Ksp expression:
\[ [A^-] = \frac{Ksp}{[M^+]} \]
- For MA:
\[ [A^-] = \frac{1.8 \times 10^{-10}}{0.01} = 1.8 \times 10^{-8} \, \text{M} \]
- For MB:
\[ [B^-] = \frac{4 \times 10^{-3}}{0.01} = 4 \times 10^{-1} \, \text{M} \]
- For MC:
\[ [C^-] = \frac{4 \times 10^{-8}}{0.01} = 4 \times 10^{-6} \, \text{M} \]
- For MD:
\[ [D^-] = \frac{6 \times 10^{-5}}{0.01} = 6 \times 10^{-3} \, \text{M} \]

4. **Compare the Required Anion Concentrations**:
- Required concentration for MA (A^-): \(1.8 \times 10^{-8} \, \text{M}\)
- Required concentration for MB (B^-): \(4 \times 10^{-1} \, \text{M}\)
- Required concentration for MC (C^-): \(4 \times 10^{-6} \, \text{M}\)
- Required concentration for MD (D^-): \(6 \times 10^{-3} \, \text{M}\)

5. **Determine Which Anion Will Precipitate First**:
The anion with the lowest required concentration for precipitation will precipitate first. Here, \(1.8 \times 10^{-8} \, \text{M}\) for A^- (from MA) is the lowest among all calculated concentrations.

### Conclusion:
The first salt to precipitate when 0.01 M solution of MX is added dropwise to the mixture will be **MA**.