# A compound containing #"36.5%"# of sulfur and #"63.5%"# of iron reacts with a compound containing #"27.6%"# oxygen and #"724%"# of iron. What is the balanced equation and the theoretical yield of iron oxide?

##### 2 Answers

The theoretical yield of the iron oxide will be **880 g**.

#### Explanation:

The first thing you have to do is determine the formula for iron sulfide by using the known percent composition of sulfur in the compound. Let's assume that the formula for iron sulfide looks like this

The percent composition of sulfur in this formula would be

This means that you have

The ratio between iron ans dulfur in rion sulfide is *have to be*

The chemical equation looks like this

Now do the same for the iron oxide.

This will get you

If you take

**3** to get

This means that your *balanced* chemical equation will look like this

Notice the **5/3 fewer moles** of the iron oxide.

Since oxygen is in excess, all the moles of iron sulfide will take part in the reaction. Use the compound's molar mass to determine how many moles you have in your **1.0-kg** sample

This means that the reaction will produce

The *theoretical yield* of the reaction will thus be

Rounded to two sig figs, the number of sig figs you gave for the mass of iron sulfide, the answer will be

The balanced equation is

The theoretical yield of

#### Explanation:

**A) BALANCED EQUATION**

In order to write a balanced chemical equation for this reaction, we must determine the formulas for iron sulfide and iron oxide, as they have more than one formula because iron forms more than one ion.

**Determine the formulas for iron sulfide and iron oxide.**

**Iron Sulfide**

S=36.5%

Fe=63.5%

Because 36.5% is 35/100, we can assume a 100-g sample of iron sulfide, and we can say that there are 36.5 g S and 63.5 g Fe. We can convert the masses to moles by dividing the mass of each element by its molar mass (atomic mass on the periodic table in grams.

**Sulfur**

**Iron**

**Mole ratios for #"Fe"# and #"S"#**

Iron and sulfur are present in a 1:1 ratio.

The formula for iron sulfide is

**Iron Oxide**

Again, because 27.6% is 27.6/100, we assume a 100-g sample of iron oxide, and we can say that there are 27.6 g oxygen and 72.4 g Fe. Again, we can convert the masses to moles by dividing the mass of each element by its molar mass (atomic mass on the periodic table in grams.

**Oxygen**

**Iron**

**Mole ratios for O and Fe**

Divide the moles of each element by the smallest number of moles.

Mole ratios must be in whole numbers, so multiply both ratios times

The mole ratio for

The chemical formula for iron oxide is

**Balanced Chemical Equation**

**B) THEORETICAL YIELD OF IRON OXIDE**

We need the molar masses of

Molar mass of

Molar mass of

Mole ratio of iron oxide and iron sulfide is:

Calculate Theoretical Yield of Iron Oxide

Convert 1 kg FeS to 1000 g FeS. Then convert the mass of FeS to moles using its molar mass. Multiply moles FeS times the mole ratio between iron oxide and iron sulfide to get moles iron oxide. Multiply moles of iron oxide times its molar mass.

(answer rounded to two significant figures because of 1.0 kg)