CHEMICAL CALCULATIONS AND STOICHIOMETRY

Chemical Stoichiometry

It is a fundamental concept in chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction.

It helps chemists determine how much of each substance is involved or produced in a reaction.

stoicheion (element) and metron (measure)

Stoichiometry comes from the Greek words,meaning the measurement of elements?

It is based on the Law of Conservation of Mass, which states that matter is neither created nor destroyed in a chemical reaction.

Mole concept

Relates the mass of a substance to the number of atoms, ions, or molecules.

Molar mass

The mass of 1 mole of a substance.

• Units: grams per mole (g/mol)

Balanced equation

Shows the stoichiometric relationship between reactants and products.

Symbol

Is an abbreviation that represents a

specific element.

Each element is represented by one or two

letters, where the first letter is always capitalized

Formula

A chemical formula is an abbreviation that

represents a compound.

It shows which elements are present and how many atoms of each element are combined.

Gives you the composition of a

compound.

Molecular Formula

Tells the actual number of atoms of each element in one molecule of a compound.

It represents the true composition of the

molecule.

Emperical Formula

Gives the simplest whole-number ratio of the atoms in a compound.

It doesn’t show the exact number of atoms, only the ratio between them.

Stractural formula

Shows the actual arrangement of atoms in space within a molecule.

It does more than just list how many atoms are present — it shows how they are bonded and connected to each other.

Atomic weight (Atomic mass)

Is the weighted average mass of all the naturally occurring isotopes of an element.

Because elements can exist as isotopes (atoms with the same number of protons but different numbers of neutrons), their atomic weights are averages based on .their abundance in nature.

Are the numbers seen on the periodic

table under each element’s symbol.

Formula weight

Is the sum of the atomic weights of all the atoms in a chemical formula (molecular or ionic).

• It tells us the mass of one formula unit of a

compound.

Emperical Formula

Represents the simplest whole-number ratio of elements in a compound.

The empirical formula weight is the sum of the atomic weights of all the atoms in that empirical formula.