Question

Use the chemical equation to complete the activity.

4Fe + 3O2 → 2Fe2O3

Iron (Fe) reacts with oxygen (O2) to form iron oxide. A scientist adds 15.4 grams of Fe to 3.6 grams of O2 to start the reaction. All of the iron and oxygen react to form iron oxide. Explain in detail how you can determine how many grams of iron oxide will be produced.

Use the law of conservation of matter in the explanation.

Answer 1

Answer:

14.54 g Fe2O3

Explanation:

The first step would be to balance the equation but since it's already balanced we don't have to worry about that.

Through the balanced equation, you can find the stoichiometry of the reaction, that is:

4 moles of Fe, react with 3 moles of O2, to produce 2 moles of Fe2O3

Chemistry (accurately stoichiometry) is all about ratios and proportions. The balanced equations gives you the standard ratio by which moles are produced.

So the next step (shown in the paper), is to convert the grams that are giving you in Moles, and you do this by dividing the number of grams given by the molar mass of the substance. The molar mass is the number of grams by which you can find exactly 6.022x10²³ molecules (one mole) of one specific substance.

15.4 g of Fe= 0.28 mol Fe

3.6 g of O2= 0.11 mol O2

Now that you have the quantity of moles, what you need to do is to look for the limitant reactant.

In a balanced equation, the number of moles in the reactants are the rules and they're gonna react completely with each other. If you want x quatity of reactants to react completely, then you will have to respect the proportion to the ratio given in the balanced equation.

But you will rarely follow the proportion so there will usually be a reactant that's gonna be limiting the reaction and one that is in excess. And how do you find this? Well, the easiest way to do it is:

• Dividing the number of moles obtained by x element the coefficients of that element in the balanced equation. The one that has the smallest ratio, is the limitant reactants.

Since the limitant reactant is gonna be limiting the reaction, all the stoichiometric procedures should be calculated through it, and in this case, the limitant reactant is O2.

But then how to establish the stoichiometric rule to find the number of Iron oxide (III) that's being produced?

Look back to the stoichiometry of the reaction:

To produce 2 moles of Fe2O3, you need 3 moles of O2.

But you have 0.11 mol O2.

Then establish a factor of conversion (shown in the picture)

The result is 0.07 mol of Fe2O3, but you need the answer in grams so you find the molar mass of Fe2O3 and then multiply it by the number of moles (0.07)

The answer is 14.54 g of Fe2O3

CHEMISTRY IS ALL ABOUT PROPORTIONS :D