LESSON 2.1: STOICHIOMETRY MYA FARRÉ
BEFORE WE START: Argument in a paragraph your opinion about the following picture. Don’t forget
to show your knowledge about the Fundamental Chemical Laws.
In my opinion is a picture that shows the fundamental chemical law but I will explain why in the
picture we can see that I have two slices of bread and one slice of cheese this is all you need to make
a sandwich. So, there you go you ve’ got your recipe. In chemistry, the recipe is the balanced
chemical equation. If I suppose that I am super hungry and I want to make 7 grilled cheese
sandwiches I need to know how much of each ingredient to use and put in a conversion factor in this
way first, write down the quantify that we know (7 grilled cheese sandwiches) next, we are going to
multiply this by the radio of bread to sandwiches. You need two slices of bread to make one
sandwich.
The recipe or balanced equation tells us the ratio of the ingredients and products. We put 2 slices of
bread on the top because that is what we are solving for and the 1 sandwich on the bottom because
that is the quantity that we started with if we multiply this the answer is 14 slices of bread.
INTRODUCTION:
Make a research of the following concepts:
a. Balancing equation methods:
A chemical equation shows us the substances involved in a chemical reaction - the substances that
react (reactants) and the substances that are produced (products). In general, a chemical equation
looks like this:
According to the law of conservation of mass, when a chemical reaction occurs, the mass of the
products should be equal to the mass of the reactants. Therefore, the amount of the atoms in each
element does not change in the chemical reaction. As a result, the chemical equation that shows the
chemical reaction needs to be balanced. A balanced chemical equation occurs when the number of the
atoms involved in the reactants side is equal to the number of atoms in the products side
b. What is stoichiometry? What is the function?
In chemistry it is very important to understand the relationship between reactants and products in a
reaction. Stoichiometry is exactly that. It is the quantitative relation between the number of moles
(and therefore mass) of various products and reactants in a chemical reaction.
Chemical reactions must be balanced, or in other words, must have the same number of various atoms
in the products as in the reactants.
If a chemical reaction is not balanced, no information about the relationship between products and
reactants can be derived. So, the first thing to do when you see a chemical reaction is to balance it.
c. Stoichiometric coefficient
Stoichiometric coefficient (ν) is the number appearing before the symbol for each compound in the
equation for a chemical reaction. By convention, it is negative for reactants and positive for products.
Stoichiometric coefficients describe the stoichiometry of the chemical reaction.
aA + bB →← cC + dD
In this equation, a, b, c and d are called as Stoichiometric coefficients of the A, B, C and D
respectively.
d. Mole ratio
