As a subject matter expert in chemistry, I can guide you through the process of finding the empirical formula from percentages. The empirical formula represents the simplest whole number ratio of elements in a compound. Here's a step-by-step guide on how to do it:


1. Determine the Mass of Each Element: Start by calculating the mass of each element in a 100 g sample of the compound. This is straightforward if you're given percentages. For instance, if a compound is made up of 72% chlorine (Cl), 24% carbon (C), and 4% hydrogen (H), you would calculate the mass of each element as follows:
- Mass of Cl = 72 g
- Mass of C = 24 g
- Mass of H = 4 g


2. Convert Masses to Moles: Use the molar mass of each element to convert the mass of each element to moles. The molar mass is the mass of one mole of an element, which can be found on the periodic table. For chlorine, carbon, and hydrogen, the molar masses are approximately:
- Molar mass of Cl = 35.45 g/mol
- Molar mass of C = 12.01 g/mol
- Molar mass of H = 1.008 g/mol

Now, calculate the moles of each element:
- Moles of Cl = \( \frac{72 \text{ g}}{35.45 \text{ g/mol}} \approx 2.03 \text{ moles} \)
- Moles of C = \( \frac{24 \text{ g}}{12.01 \text{ g/mol}} \approx 1.99 \text{ moles} \)
- Moles of H = \( \frac{4 \text{ g}}{1.008 \text{ g/mol}} \approx 3.97 \text{ moles} \)


3. Determine the Smallest Number of Moles: Look at the number of moles you've calculated and find the smallest number. This will help you to express the ratio of the elements in the simplest form. In our example, the smallest number of moles is approximately 1.99 (for carbon).

4. **Divide Each Number of Moles by the Smallest Number**: To find the simplest whole number ratio, divide the number of moles of each element by the smallest number of moles:
- Ratio of Cl = \( \frac{2.03}{1.99} \approx 1.02 \)
- Ratio of C = \( \frac{1.99}{1.99} = 1 \)
- Ratio of H = \( \frac{3.97}{1.99} \approx 2 \)


5. Round to the Nearest Whole Number: Since we're looking for whole numbers, round the ratios to the nearest whole number. In this case, the ratios are already close to whole numbers, so we can keep them as is:
- Ratio of Cl ≈ 1
- Ratio of C = 1
- Ratio of H ≈ 2


6. Write the Empirical Formula: Finally, write the empirical formula using the whole number ratios you've found:
- Empirical formula: \( \text{C} \cdot \text{Cl} \cdot 2\text{H} \)

This process ensures that you have the simplest whole number ratio of elements in the compound, which is the empirical formula.

Now, let's move on to the next step.

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For this example, our compound has 72% Cl, 24% C and 4% H. First, determine the mass of each of the elements in 100 g of the substance. Next, determine how many moles there are of each element in 100 g of the substance by using the molar mass of each element. Divide each one by the smallest number of moles.read more >>