Types of Reactions

1. Combination Reaction / Addition Reaction

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

A+BAB2H2+O22H2OA + B \longrightarrow AB \newline 2H_2 + O_2 \rightleftharpoons 2H_2O

\rightleftharpoonsmeans the reaction can work both ways

2. Decomposition Reaction

Where a compound gets split into it's constituents

ABA+B2H2O2H2+O2AB \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+BCB+ACFe+CuSO4Cu+FeSO4A + 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+DAD+CBNaCl+AgNO3NaNO3+AgCl A^+B^- +C^+D^- \longrightarrow AD + CB \newline NaCl + AgNO_3 \longrightarrow NaNO_3 + AgCl \downarrow

\downarrowmeans precipitation. In the above case, Silver Chloride will settle to the bottom of the Sodium Nitrate solution \uparrowstands for effervesence (gas released via bubbles)

5. Neutralization Reaction

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

Acid+BaseSalt+WaterNaOH+HClNaCl+H2O 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

2H2+O22H2O2H_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

2NO22NO+O22NO_2 \rightleftharpoons 2NO+O_2 \uparrow

Nitrate will change to Nitrogen Oxide and Oxygen above 50°c50\degree cand Nitrogen Oxide and Oxygen will change back to Nitrate below 50°c50\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+O22MgOMg + O_2 \longrightarrow 2MgO

Reduction Reaction

This is when oxygen is removed and hydrogen is added

PbO2+4HClPbCl2+Cl2+2H2OPbO_2 + 4HCl \longrightarrow PbCl_2 + Cl_2 + 2H_2O

Redox = Red(uction) + Ox(idation)

Both, together

Mg+H2SO4MgSO4+H2OMg + 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)