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To solve this problem, let's go through the steps for determining the empirical formula (RE) and molecular formula (RM) of the compound based on the given data.

### Problem Data
- **Molar mass (Mr) of lactic acid:** 270 g/mol
- **Elemental composition by mass:**
  - Carbon (C): 40%
  - Hydrogen (H): 6.6%
  - Oxygen (O): 53.4%

### Step 1: Assume a 100-gram Sample
If we assume we have 100 grams of this compound, the masses of each element would be:
- Mass of C: \( 40 \, \text{g} \)
- Mass of H: \( 6.6 \, \text{g} \)
- Mass of O: \( 53.4 \, \text{g} \)

### Step 2: Convert Masses to Moles
Next, we convert the mass of each element to moles using their atomic masses:
- **Atomic mass of C:** 12 g/mol
- **Atomic mass of H:** 1 g/mol
- **Atomic mass of O:** 16 g/mol

Calculations:
\[
\text{Moles of C} = \frac{40}{12} \approx 3.33
\]
\[
\text{Moles of H} = \frac{6.6}{1} = 6.6
\]
\[
\text{Moles of O} = \frac{53.4}{16} \approx 3.34
\]

### Step 3: Determine the Empirical Formula
To find the simplest ratio, we divide each mole quantity by the smallest number of moles (approximately 3.33).

\[
\text{Ratio of C} = \frac{3.33}{3.33} = 1
\]
\[
\text{Ratio of H} = \frac{6.6}{3.33} \approx 2
\]
\[
\text{Ratio of O} = \frac{3.34}{3.33} \approx 1
\]

The empirical formula (RE) of the compound is thus:
\[
\text{C}_1\text{H}_2\text{O}_1 \Rightarrow \text{CHO}_2
\]

### Step 4: Determine the Molecular Formula
To find the molecular formula, we need to compare the empirical formula mass with the molar mass of the compound.

1. **Empirical formula mass of CHO:** \( 12 + 2 + 16 = 30 \, \text{g/mol} \)
2. **Molar mass given:** 270 g/mol

Now, we find the factor \( n \) by dividing the molar mass by the empirical formula mass:
\[
n = \frac{270}{30} = 9
\]

3. Multiply each subscript in the empirical formula by this factor:
\[
\text{Molecular formula} = \text{C}_{1 \times 9}\text{H}_{2 \times 9}\text{O}_{1 \times 9} = \text{C}_9\text{H}_{18}\text{O}_9
\]

### Final Answer
- **Empirical formula (RE):** CHO
- **Molecular formula (RM):** \( \text{C}_9\text{H}_{18}\text{O}_9 \)

Would you like further details, or do you have any questions?

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Here are some related questions to deepen understanding:

1. How is the empirical formula different from the molecular formula?
2. What is the significance of using the molar mass to determine the molecular formula?
3. How would the process change if the molar mass was unknown?
4. Can a compound have the same empirical and molecular formula? Explain.
5. How would you find the empirical formula if percentages did not add up to 100%?

**Tip:** When calculating molecular formulas, always confirm the compound's molar mass to ensure accuracy.

Selama aktivitas fisik berlebihan, asam laktat (Mr = 270) dapat dihasilkan pada jaringan otot akibat kekurangan oksigen. Hasil analisis unsur menunjukkan bahwa senyawa ini mengandung 40% C, 6,6% H, dan 53,4% O. Tentukanlah rumus molekul empiris (RE) dan rumus molekul (RM) senyawa tersebut!

Calculate the empirical and molecular formula of lactic acid given its molar mass (270 g/mol) and elemental composition (40% C, 6.6% H, 53.4% O). A step-by-step solution demonstrates stoichiometric calculations and mole ratios for high school chemistry students.

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