Bell Work

• Convert the following in to a word equation:

• H2 + O2 → H2O

Physical Science – Lecture 50

Types of Reactions

Elements

• Have only 1 capital letter – can be found on the periodic table.

Compounds

• Have more than 1 capital letter

Types of Reactions

• 1. Direct Union (or Combination) Reactions• 2. Combustion Reactions• 3. Single Displacement Reactions• 4. Double Displacement (or Metathesis)

Reactions• 5. Decomposition Reactions

1. Direct Union or Combination Reactions

• A reaction where two or more elements or compounds make one compound.

Example

• H2 + Br2 → HBr

2. Combustion Reactions

• A compound reacts with an element to form two compounds.

All Combustion Reactions

• Combustion reactions occur between a hydrocarbon and oxygen.

• The reaction forms carbon dioxide and water.

What is a hydrocarbon?

• A hydrocarbon is a compound that only contains hydrogen and carbon.

• Occasionally, it will contain oxygen.

Examples

• C3H8 + 5 O2 → 3 CO2 + 4 H2O

• 2 C4H10 + 9 O2 → 8 CO2 + 10 H2O

• C2H5OH + 3 O2 → 2 CO2 + 3 H2O

3. Single Displacement Reactions

• An element reacts with a compound to form a new element and compound.

Example

• Al + HgCl2 → AlCl3 + Hg

Example

• Cu + 2 AgNO3 → Cu(NO3)2 + 2 Ag

• Fe + CuSO4 → FeSO4 + Cu

Example

• Cl2 + 2 NaI → 2 NaCl + I2

4. Metathesis or Double Displacement Reactions

• Double Displacement occurs when two compounds react to form two new compounds.

• It usually occurs in water solutions.

What must happen?

• One or both of the products must become unavailable for the reverse reaction or the reaction will not happen.

Three Ways to Prevent Reversal

• (1) Formation of an insoluble compound• (2) Formation of a gas – that leaves the

solution• (3) Formation of water – neutralization

reaction

Examples

• Na2S (aq) + 2HCl (aq) → 2NaCl (aq) + H2S (g)

• AgNO3 + NaCl → AgCl(s) + NaNO3

• BaCl2 + K2SO4 → BaSO4(s) + 2 KCl

• HCl + NaOH → NaCl + H2O

• H2SO4 + Mg(OH)2 → MgSO4 + H2O

5. Decomposition Reactions

• Decomposition is the reverse of combination/direct union.

• A single compound is broken down into two or more elements/compounds.

Decomposition Example

• Cu(NO3)2 → CuO + NO2 + O2

• 2 HgO → 2 Hg + O2

• 2 KClO3 → 2 KCl + 3 O2

• CaCO3 → CaO + CO2

How to Predict Reaction Types

• Step 1 – Identify the reactants and products as elements or compounds.

• Step 2 – Find the reaction type that has the same pattern as what’s labeled in Step 1.

•

Examples

N2 + H2 → NH3

SiCl4 + H2O → H4SiO4 + HCl

Si2H3 + O2 → SiO2 + H2

Al(OH)3 + H2SO4 → Al2(SO4)3 + H2O

C7H16 + O2 → CO2 + H2O

Iron + Water → Iron III oxide + Hydrogen

Ammonium nitrate → Dinitrogen monoxide + water

When copper reacts with silver nitrate, solid silver crystals and copper (II) nitrate are formed. •

When C5H9O reacts with oxygen gas, carbon dioxide and water are formed.

When lithium hydroxide reacts with hydrogen bromide, lithium bromide and

water are formed.