# 1. Combination Reaction / Addition Reaction

This is a reaction where two compounds/atoms are combining to form another compound

$A + B \longrightarrow AB \newline 2H_2 + O_2 \rightleftharpoons 2H_2O$

$\rightleftharpoons$means the reaction can work both ways

# 2. Decomposition Reaction

Where a compound gets split into it's constituents

$AB \longrightarrow A + B \newline 2H_2O \rightleftharpoons 2H_2 + O_2$

# 3. Displacement Reaction

Where one element (more reactive) replaces another element (less reactive) to replace it in it's compound

$A + BC \longrightarrow B + AC \newline Fe + CuSO_4 \longrightarrow Cu + FeSO_4$

# 4. Double Displacement Reaction

Where two elements swap positions in their compounds

$A^+B^- +C^+D^- \longrightarrow AD + CB \newline NaCl + AgNO_3 \longrightarrow NaNO_3 + AgCl \downarrow$

$\downarrow$means precipitation. In the above case, Silver Chloride will settle to the bottom of the Sodium Nitrate solution $\uparrow$stands for effervesence (gas released via bubbles)

# 5. Neutralization Reaction

An acid will react with a base to form a salt and water

$Acid + Base \longrightarrow Salt + Water \newline NaOH + HCl \longrightarrow NaCl + H_2O$

Every double displacement reaction is a neutralization reaction but every double displacement reaction is not a neutralization reaction

# 6. Reversible Reaction

These reactions can go both ways, depending on conditions

$2H_2+O_2 \rightleftharpoons 2H_2O$

Water is formed when heat is supplied, broken back into hydrogen and oxygen via electrolysis

# 7. Thermal Disassociation Reaction

These are reversible reactions that can go from one form to the other depending on temperature

$2NO_2 \rightleftharpoons 2NO+O_2 \uparrow$

Nitrate will change to Nitrogen Oxide and Oxygen above $50\degree c$and Nitrogen Oxide and Oxygen will change back to Nitrate below $50\degree c$

Every thermal disassociation reaction is a reversible reaction but every reversible reaction is not a thermal disassociation reaction

# 8. Redox Reaction

## Oxidation Reaction

This is when oxygen is added and hydrogen is removed

$Mg + O_2 \longrightarrow 2MgO$

## Reduction Reaction

This is when oxygen is removed and hydrogen is added

$PbO_2 + 4HCl \longrightarrow PbCl_2 + Cl_2 + 2H_2O$

## Redox = Red(uction) + Ox(idation)

Both, together

$Mg + H_2 SO_4 \longrightarrow MgSO_4+ H_2O \uparrow$

## How to identify a Redox reaction

1. Oxygen/Hydrogen Consideration (Manually Check, 9th grade level)

2. By losing/gaining of electrons (Higher Level)

3. Oxidation State / Number (Higher Level)