Stoichiometry Day 1

Stoichiometry

the relationship between substances that are included in reactions and solutions. This includes conversions of different measurements in order to show and give accurate proportions in reactions.

Conversions

• Molecules/particles/molecules/formula units -> moles

• Grams -> moles

• Mole to mole ratio

Avogrado's Number (6.022 x 10²³)

a constant that is used in stoichiometry problems when atoms or molecules are involved

Mass (in grams) -> moles

the amount of mass given = 1 mole

Periodic Table

We use the periodic table in order to determine our molar mass

Examples: Compound masses

• CH4 = 16g (1 mole of methane)

• H2O = 18g (1 mole of water)

• CO2 = 44g (1 mole of carbon dioxide)

• NH4 = 18g (1 mole of ammonia)

Explanation

When calculating the mass of a compound or substance one must look at the periodic table.

As you know CH₄ has 1 Carbon atom and 4 Hydrogen atoms. If you look at the periodic table, you will see that Carbon's relative atomic mass is 12 and Hydrogen's relative atomic mass is 1.

Since there is only one carbon atom that is 12 grams, and because there are 4 hydrogen atoms in CH₄ that adds another 4 grams to the compound. Adding the carbon and hydrogens together would mean you are adding the masses as well; therefore your relative molar mass would be 16g.

Multiple Choice

What is the molar mass of Cl₂?

• 17 g/mol

• 35 g/mol

• 70 g/mol

• 89 g/mol

Multiple Choice

What is the molar mass of CO₂?

• 22

• 16

• 32

• 44

Multiple Choice

What is the molar mass of table salt (NaCl)?

• 805 g/mol

• 35 g/mol

• 23 g/mol

• 58 g/mol