Chemistry 4 Fundamentals of inprganic chemistry & stoichimetry

Inorganic compounds (main groups)

1. Oxides

2. Hydroxides

3. Acids

4. Salts

What even is stoichiometry?

A scientific way of measuring elements and other chemicals in a chemical reaction

Oxides

Compounds containing oxygen combined with another element

→ example: CO2 (Carbon dioxide), Na2O (sodium dioxide)

Types of oxides:

Metals oxides → usually basic (CaO)

Non-metal oxides → often acidic (CO2)

Hydroxides

Compounds containing OH- Group

Many hydroxides are: Bases

Examples: NaOH (Sodium hydroxide), Ca(OH)2 (Calcium hydroxide),

Why are many hydroxides bases?

Because they release OH⁻ ions in water

Acids

Substance that release: H⁺ ions in water

Examples: HCl (hydrochloric acids), H₂SO₄ (sulfric acid)

Salts

Ionic compounds usually formed by:

Acid + base

Example:

HCl + NaOH → NaCl + H₂O

Salt: NaCl

Atomic mass

Mass of 1 atom of a single chemical element

Measured in: atomic mass units (u)

(written in periodic table, often called atomic weight)

Molecular mass

Sum of atomic masses in a single molecule

Example: H2O H=1, O=16

→ molecular mass = 2(1)+16 =18 u

Mole concept (Definition)

a mole is the amount of substance containing: Avogadro‘s number of particles 6.022 × 10²³ particles/mol

Particles can be: atoms, molecules, ions

unit for molar mass: g/mol

Molar mass → mass of 1 mole of a substance

Example: H2O

Molar mass= 18 g/mol (PERIODIC TABLE GIVES ATOMIC MASS, WHICH IS EUQAL TO MOLAR MASS IN GRAMS/MOL)

Therefore: 1 mole water = 18g

What’s the amount of the Avogardo‘s number bzw. how many particles/molecules does one mole contain?

6.022 × 10²³ particles/mol

→ for understanding: a mole is just a very large number of things

Stoichiometry (Definition & steps of stoichiometry problems & 1 important rule)

Definition: calculations involving quantities of reactants and products

Based on: balanced chemical equations

Steps:

1. write balanced equations

2. Convert given quantity to moles

3. Use mole ratio

4. Convert to required units

Rule: atoms must be equal on both sides

Example:

2H₂ + O₂ → 2H₂O

Meaning:

2 moles H₂ react with:

1 mole O₂

to produce:

2 moles H₂O

Types of chemical reactions (stoichiometry)

1. Combination Reaction:

2 subs form 1 product

A + B → AB

2. Decomposition Reaction:

1 compound breaks apart

AB → A + B

3. Single Replacement:

1 element replaces another

A + BC → AC + B

4. Double Replacement:

2 compounds exchange ions

AB + CD → AD + CB

5. Combustion:

usually Hydrocarbon + oxygen → CO₂ + H₂O

Example:

CH₄ + O₂ → CO₂ + H₂O

„Chemical equations can have different numbers of atoms“

WRONG → atoms are conserved (means the total number of each type of atom does NOT change during a chemical reaction)

→ in chemical equation you must have the exact same number of atoms on the left (reactant) side as on the right (product) side

→ atoms CAN NOT disappear!