for which one of the following minerals, the composition gives is incorrect ?

Options

A. Soda ash-`(Na_(2)CO_(3))`
B. Carnallite-`(KCl.MgCl_(2).6H_(2)O)`
C. Borax-`(Na_(2)B_(4)O_(7).7H_(2)O)`
D. glauber's salt-`(Na_(2)SO_(4).10H_(2)O)`

Explanation

To solve the question regarding which mineral has an incorrect composition, we will analyze the given minerals and their respective compositions step by step.

### Step 1: Identify the minerals and their compositions
We have four minerals to consider:
1. Soda Ash
2. Carnalite
3. Borax
4. Glauber's Salt

### Step 2: Analyze each mineral's composition

**1. Soda Ash:**
- Composition: Na2CO3
- Analysis: Soda ash is indeed sodium carbonate, and its formula is correctly represented as Na2CO3.
- Conclusion: This composition is correct.

**2. Carnalite:**
- Composition: KCl·MgCl2·6H2O
- Analysis: Carnalite is a double salt of potassium and magnesium, and its composition is accurately represented as KCl·MgCl2·6H2O.
- Conclusion: This composition is correct.

**3. Borax:**
- Composition: Na2B4O7·7H2O
- Analysis: Borax is a mineral of sodium and is correctly represented by the formula Na2B4O7·10H2O. The provided composition states 7H2O, which is incorrect.
- Conclusion: This composition is incorrect.

**4. Glauber's Salt:**
- Composition: Na2SO4·10H2O
- Analysis: Glauber's salt is the hydrated form of sodium sulfate, and its formula is correctly represented as Na2SO4·10H2O.
- Conclusion: This composition is correct.

### Step 3: Determine the incorrect composition
From our analysis, we found that:
- Soda Ash: Correct
- Carnalite: Correct
- Borax: Incorrect (should be Na2B4O7·10H2O)
- Glauber's Salt: Correct

Thus, the mineral with the incorrect composition is **Borax**.

### Final Answer:
The mineral for which the composition is incorrect is **Borax**.

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