00:02
In stoichiometry, we relate the quantities of the substances that are involved in a chemical reaction.
00:08
In this problem, we will be given the balance chemical equation for the reaction of iron with oxygen to form iron 3 oxide.
00:23
If we have 7 .50 grams of iron reacting with 2 grams of oxygen, we wish to find the mass of iron 3 oxide to be formed.
00:36
From the coefficients in the balance equation, we say that for every 4 moles of fe that react, 3 moles of no2 are needed to form 1 mole of fe2o3.
00:50
Let us find the mass of fe2o3 that is formed from each of the given mass of the reactants, say from 7 .50 grams of fe.
01:00
To do that, we have to first convert 7 .50 grams of fe into moles of fe by dividing it by its own molar mass, which is 55 .85 grams per mole.
01:15
Then, we apply the mole ratio that for every 4 moles of fe, we form 1 mole of fe2o3.
01:25
Finally, we multiply by the molar mass of fe2o3 in order to convert this into mass.
01:33
The molar mass of fe2o3 is 159 .7.
01:41
We solve this and we get 5 .36 grams.
01:48
We will do the same, but this time from 2 grams of oxygen...