1. អំបិល កាល់ស្យូមរបស់ម៉ូណូអាសុីតកាបុកសុីលិច ឆ្អែតមួយ មានកាល់ស្យូម 2g  ក្នុងអំបិល 7.9g ។ តើអាសុីត នេះមានរូបមន្តដូចម្តេច?
  Please tell me

To find the molecular formula of the carboxylic acid, we need to analyze the given data. Here's the step-by-step process:

1. **Given Data:**
   - Mass of calcium (Ca) in the salt: 2 g
   - Mass of the salt: 7.9 g

2. **Molar Mass of Calcium (Ca):**
   - The atomic mass of calcium is approximately 40 g/mol.

3. **Number of Moles of Calcium:**
   \[
   \text{Moles of Ca} = \frac{\text{Mass of Ca}}{\text{Molar mass of Ca}} = \frac{2 \text{ g}}{40 \text{ g/mol}} = 0.05 \text{ mol}
   \]

4. **Molar Mass of the Salt:**
   - The molar mass of the salt is equivalent to the mass of the salt divided by the number of moles of calcium:
   \[
   \text{Molar mass of salt} = \frac{\text{Mass of salt}}{\text{Moles of Ca}} = \frac{7.9 \text{ g}}{0.05 \text{ mol}} = 158 \text{ g/mol}
   \]

5. **Identifying the Acid:**
   - The salt is a calcium salt of a monocarboxylic acid, which means the acid has a carboxyl group (-COOH).
   - Calcium typically forms a salt by replacing two hydrogen atoms, implying that the acid has two acidic hydrogens (i.e., it is a dicarboxylic acid).

6. **General Formula:**
   - For a dicarboxylic acid, the formula is generally \( \text{HOOC-R-COOH} \).
   - The molar mass of the calcium salt \( \text{Ca(C_xH_yO_4)} \) should be 158 g/mol.

7. **Calculation:**
   - Let \( \text{R} \) represent the hydrocarbon chain. The formula of the salt can be expressed as \( \text{Ca(C}_x\text{H}_y\text{O}_4\text{)} \).
   - The molar mass of calcium is 40 g/mol, and since we have two carboxyl groups and two calcium ions:

   \[
   \text{Molar mass of the salt} = 40 + (12x + y + 64)
   \]
   \[
   158 = 40 + (12x + y + 64)
   \]
   \[
   158 = 104 + 12x + y
   \]
   \[
   54 = 12x + y
   \]

8. **Assuming the simplest ratio:**
   - \( x = 2 \) and \( y = 2 \) (which is \( C_2H_2 \)) fits this equation, implying the simplest molecular formula.
   - Hence, the carboxylic acid is likely oxalic acid \( \text{H}_2\text{C}_2\text{O}_4 \).

**Conclusion:**
- The carboxylic acid is oxalic acid \( \text{H}_2\text{C}_2\text{O}_4 \), and the calcium salt is calcium oxalate \( \text{Ca(C}_2\text{O}_4\text{)} \).

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Would you like more details on this explanation or have any questions?

Here are some related questions:
1. How do you determine the empirical formula from given mass data?
2. What is the significance of using molar mass in chemical calculations?
3. Can you explain how to find the molecular formula if only the empirical formula is known?
4. What are some common examples of carboxylic acids and their uses?
5. How does calcium form salts with different acids?
6. What are the physical properties of oxalic acid and calcium oxalate?
7. How can you experimentally determine the molecular mass of an unknown compound?
8. Why are certain acids considered dicarboxylic acids?

**Tip:** Always verify the simplest integer ratio when determining molecular formulas to ensure accuracy.

Learn how to determine the molecular formula of a carboxylic acid salt using chemical calculations. This problem involves calculating the molar mass, determining empirical formulas, and deriving molecular formulas from given mass data.

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