Which of the following precipitate(s) is/are dissolved to colourless solution on adding sufficient amount of dilute HCl?

Options

A. `CaCO_(3)`
B. `BaCrO_(4)`
C. `MgC_(2)O_(4)`
D. `BaSO_(4)`

Explanation

To determine which precipitate(s) dissolve to a colorless solution upon the addition of sufficient dilute HCl, we will analyze each option step by step.

### Step 1: Analyze the first option (CaCu3)
- When calcium copper(II) carbonate (CaCu3) is treated with dilute HCl, it reacts to form calcium chloride (CaCl2) and copper(II) chloride (CuCl2).
- The reaction can be represented as:
\[ CaCu3 + 2HCl \rightarrow CaCl2 + CuCl2 + H2O \]
- Both CaCl2 and CuCl2 are colorless solutions.
- **Conclusion**: This option is correct.

### Step 2: Analyze the second option (BaCrO4)
- When barium chromate (BaCrO4) is treated with dilute HCl, it forms barium chloride (BaCl2) and dichromic acid (H2Cr2O7).
- The reaction can be represented as:
\[ BaCrO4 + 2HCl \rightarrow BaCl2 + H2Cr2O7 \]
- H2Cr2O7 is orange in color.
- **Conclusion**: This option is incorrect since the solution is not colorless.

### Step 3: Analyze the third option (Mg2C2O4)
- When magnesium oxalate (Mg2C2O4) is treated with dilute HCl, it reacts to form magnesium chloride (MgCl2) and oxalic acid (H2C2O4).
- The reaction can be represented as:
\[ Mg2C2O4 + 4HCl \rightarrow 2MgCl2 + H2C2O4 \]
- Both MgCl2 and H2C2O4 are colorless solutions.
- **Conclusion**: This option is correct.

### Step 4: Analyze the fourth option (BaSO4)
- Barium sulfate (BaSO4) does not react with dilute HCl.
- There is no change in the solution, and it remains as a precipitate.
- **Conclusion**: This option is incorrect.

### Final Conclusion:
The precipitates that dissolve to form colorless solutions upon the addition of sufficient dilute HCl are:
- **Option 1: CaCu3**
- **Option 3: Mg2C2O4**