Which of the following ores is a double salt composition

Options

A. Carnallite
B. Alum
C. Dolomite
D. Cerrusite

Explanation

To determine which of the given ores is a double salt composition, we need to analyze the chemical compositions of each ore provided in the question. A double salt is defined as a salt that contains two different cations or anions, and it can be represented by the formula of two different salts combined.

### Step-by-Step Solution:

1. **Identify the Ores and Their Compositions:**
- **First Ore: Carallite (KCl·MgCl2·6H2O)**
- Contains KCl (Potassium Chloride) and MgCl2 (Magnesium Chloride).
- It has two different salts present.

2. **Check if Carallite is a Double Salt:**
- Since Carallite contains two different salts (KCl and MgCl2), it qualifies as a double salt composition.

3. **Second Ore: Alum (K2SO4·Al2(SO4)3·24H2O)**
- Contains K2SO4 (Potassium Sulfate) and Al2(SO4)3 (Aluminum Sulfate).
- It also has two different salts present.

4. **Check if Alum is a Double Salt:**
- Since Alum contains two different salts (K2SO4 and Al2(SO4)3), it qualifies as a double salt composition.

5. **Third Ore: Dolomite (CaCO3·MgCO3)**
- Contains CaCO3 (Calcium Carbonate) and MgCO3 (Magnesium Carbonate).
- It has two different salts present.

6. **Check if Dolomite is a Double Salt:**
- Since Dolomite contains two different salts (CaCO3 and MgCO3), it qualifies as a double salt composition.

7. **Fourth Ore: Cerusite (PbCO3·MgCO3)**
- Contains PbCO3 (Lead Carbonate) and MgCO3 (Magnesium Carbonate).
- However, it primarily consists of PbCO3.

8. **Check if Cerusite is a Double Salt:**
- Since Cerusite primarily consists of PbCO3 and does not have two different salts in the same way as the others, it does not qualify as a double salt composition.

### Conclusion:
The ores that are double salt compositions are:
- Carallite (KCl·MgCl2·6H2O)
- Alum (K2SO4·Al2(SO4)3·24H2O)
- Dolomite (CaCO3·MgCO3)

The only ore that does not qualify as a double salt composition is Cerusite (PbCO3·MgCO3).