Question

A compound composed of sulfur and fluorine is found to contain 62.79% by mass of sulfur. if the approximate molar mass of this compound is 102.13 g/mol, what is its molecular formula?

Answer 1

Let our basis for answering this item be 1 mol of the given substance. Then, we calculate for the equivalent mass by multiplying the number of moles with the molar mass.
                  mass = (102.13 g/mol)(1 mol) = 102.13 g of substance

Then, we calculate for the amount of sulfur and fluorine each using the percentage given.
     sulfur = (0.6279)(102.13 g) = 64.13 g of sulfur
     fluorine = (1 - 0.6279)(102.13 g) = 38 g of fluorine

Then, calculate for the number of moles of the sulfur and fluorine by dividing the calculated mass by the molar mass of each.
     moles of sulfur = (64.13 g)(1 mol/32 g) = 2 mols suflur
     moles of fluorine = (38 g)(1 mol/19 g) = 2 mols fluorine

The molecular formula of the substance is S₂F₂. 

ANSWER: S₂F₂

Answer 2

The molecular formula of the compound of sulfur and fluorine is $\boxed{{{\text{S}}_2}{{\text{F}}_2}}$.

Further Explanation:

Empirical formula:

It is atom’s simplest positive integer ratio in compound. It may or may not be the same as that of molecular formula. For example, empirical formula of disulfur dioxide is ${\text{SO}}$.

Molecular formula:

It is chemical formula that indicates the total number and kinds of atoms in molecule. For example, molecular formula of disulfur dioxide is ${{\text{S}}_2}{{\text{O}}_2}$

Step 1: Mass of sulfur (S) and fluorine (F) is to be calculated. This is done by using equation (1).

Since the given compound contains only sulfur and fluorine. So the mass of sulfur is calculated as follows:

${\text{Mass of sulfur}}\left( {\text{S}} \right) = {\text{Mass of compound}} \times {\text{percentage of Sulfur}}$      ......(1)

The mass of the compound is 102.13 g/mol.

The percentage of sulfur is 62.79 %.

Substitute the values in equation (1).

$\begin{aligned}{\text{Mass of sulfur}}\left( {\text{S}} \right) &= 102.13{\text{ g/mol}} \times 62.79{\text{ }}\%\\&= 102.13{\text{ g/mol}} \times \frac{{62.79}}{{100}}\\&= 64.13{\text{ g/mol}}\\\end{aligned}$

The mass offluorine (F) is calculated as follows:

${\text{Mass of fluorine}}\left( {\text{F}} \right) = {\text{Mass of compound}} - {\text{Mass of sulfur}}\left( {\text{S}} \right)$   ......(2)

Substitute 102.13 g/mol for mass of the compound and 64.13 g/mol for mass of sulfur in equation (2).

$\begin{aligned}{\text{Mass of fluorine}}\left({\text{F}} \right) &= {\text{102}}{\text{.13 g/mol}} - {\text{64}}{\text{.13 g/mol}}\\&= 38{\text{ g/mol}}\\\end{aligned}$

Step 2: The number of sulfur (S) and fluorine (F) in the compound is to be calculated.

The formula to calculate the number of sulfur (S)atoms in the molecule is as follows:

${\text{Number of S}} = \dfrac{{{\text{Given mass of S}}}}{{{\text{Molar mass of S}}}}$                              ......(3)

The given mass of S is 64.13 g/mol.

The molar mass of S is 32 g/mol.

Substitute these values in equation (3).

$\begin{aligned}{\text{Number of S}} &= \frac{{{\text{64}}{\text{.13 g/mol}}}}{{{\text{32 g/mol}}}} \\&\approx 2\\\end{aligned}$

The formula to calculate the number of fluorine (F) atoms in the molecule is as follows:

${\text{Number of F}} = \dfrac{{{\text{Given mass of F}}}}{{{\text{Molar mass of F}}}}$                      ......(4)

The given mass of F is 38 g/mol.

The molar mass of F is 19 g/mol.

Substitute these values in equation (4).

$\begin{aligned}{\text{Number of F}} &= \frac{{{\text{38 g/mol}}}}{{{\text{19 g/mol}}}}\\&= 2\\\end{aligned}$

Hence the molecular formula of the given compound is ${{\mathbf{S}}_{\mathbf{2}}}{{\mathbf{F}}_{\mathbf{2}}}$.

Learn more:

1. Calculate the moles of ions in the solution: brainly.com/question/5950133

2. Calculate the moles of chlorine in 8 moles of carbon tetrachloride: brainly.com/question/3064603

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Stoichiometry of formulas and equations

Keywords: empirical formula, S, F, SF, S2F2, subscript, moles of F, moles of S, mass of S, mass of F and molecular formula.