Question

A compound is found to contain 10.85 % silicon , 27.40 % chlorine , and 61.75 % bromine by mass. To answer the question, enter the elements in the order presented above. QUESTION 1: The empirical formula for this compound is . QUESTION 2: The molar mass for this compound is 258.8 g/mol. The molecular formula for this compound is

Answer 1

1. Empirical Formula:
`\( \text{SiCl}_2\text{Br}_2 \)`

2. Molecular Formula:
`\( \text{SiCl}_2\text{Br}_2 \)`

To determine the empirical formula and molecular formula, we can use the given percentages and molar mass.

Let's assume we have 100 g of the compound, and then we can determine the number of moles of each element.

1. **Calculate the moles of each element:**

- Silicon (Si):

`\[ \text{moles of Si} = \frac{10.85 \, \text{g}}{28.09 \, \text{g/mol}} \]`

- Chlorine (Cl):

`\[ \text{moles of Cl} = \frac{27.40 \, \text{g}}{35.45 \, \text{g/mol}} \]`

- Bromine (Br):

`\[ \text{moles of Br} = \frac{61.75 \, \text{g}}{79.90 \, \text{g/mol}} \]`

2. **Determine the mole ratios:**

- Divide each mole value by the smallest of the three.

- Round the ratios to the nearest whole number.

3. **Write the empirical formula:**

- The ratios obtained represent the subscripts of the elements in the empirical formula.

4. **Calculate the molar mass of the empirical formula:**

- Sum the molar masses of the elements in the empirical formula.

5. **Determine the molecular formula:**

- Use the given molar mass (258.8 g/mol) and the molar mass of the empirical formula.

Now, let's calculate:

`\[ \text{Moles of Si} = \frac{10.85 \, \text{g}}{28.09 \, \text{g/mol}} \approx 0.386 \]`

`\[ \text{Moles of Cl} = \frac{27.40 \, \text{g}}{35.45 \, \text{g/mol}} \approx 0.772 \]`

`\[ \text{Moles of Br} = \frac{61.75 \, \text{g}}{79.90 \, \text{g/mol}} \approx 0.773 \]`

The mole ratios (rounded) are approximately:

`\[ \text{Si : Cl : Br} \approx 1 : 2 : 2 \]`

The empirical formula is
`\( \text{SiCl}_2\text{Br}_2 \).`

The molar mass of the empirical formula is calculated as follows:

`\[ (1 * \text{molar mass of Si}) + (2 * \text{molar mass of Cl}) + (2 * \text{molar mass of Br}) \]`

`\[ = (1 * 28.09) + (2 * 35.45) + (2 * 79.90) \]`

`\[ = 28.09 + 70.90 + 159.80 \]`

`\[ = 258.79 \, \text{g/mol} \]`

Since the molar mass of the empirical formula matches the given molar mass (258.8 g/mol), the molecular formula is the same as the empirical formula:
`\( \text{SiCl}_2\text{Br}_2 \).`

The probable question may be:

A compound is found to contain 10.85 % silicon , 27.40 % chlorine , and 61.75 % bromine by mass. To answer the question, enter the elements in the order presented above. QUESTION 1: The empirical formula for this compound is ____? QUESTION 2: The molar mass for this compound is 258.8 g/mol. The molecular formula for this compound is ___?