List Of Important Chemical Reactions Year 12 Students Must Know

Do you find yourself flipping through pages of notes just to find a particular chemical reaction? Well, you don’t have to do that anymore! Here are all the important chemical reactions Year 12 students must know!

 

Table of contents:

1. Module 5: Equilibrium and Acid Reactions
2. Module 6: Acid/Base Reactions
3. Module 7: Organic Chemistry
4. Additional Reactions

 

Module 5: Equilibrium and Acid Reactions

Combustion of metals

Word equation: metal + oxygen → metal oxide

Examples:

Burning magnesium: \( 2Mg_{(s)} \ + \ O_{2(g)} \ → \ 2M_{g}O_{(s)} \)

Burning steel wool: \( 4Fe_{(s)} \ + \ 3O_{2(g)} \ → \ 2Fe_{2}O_{3(s)} \)

 

 

Combustion of hydrocarbons and alcohols

1. Complete combustion produces carbon dioxide and water.

Examples:

Hydrocarbon: \( C_{3}H_{8(g)} \ + \ 5O_{2(g)} \ → \ 3CO_{2(g)} \ + \ 4H_{2}O_{(l)} \)

Alcohol: \( C_{2}H_{5}OH_{(l)} \ + \ 3O_{2(g)} \ → \ 2CO_{2(g)} \ + \ 3H_{2}O_{(l)} \)

 

2. Incomplete combustion occurs when insufficient oxygen is present for a complete reaction to occur.

Water and carbon monoxide (\(CO_{(g)}\)) and/or soot (\(C_{(s)}\)) are produced in an incomplete combustion.

 

 

Photosynthesis

Word equation: carbon dioxide + water → glucose + oxygen

Chemical equation: \( 6CO_{2(g)} \ + \ 6H_{2}O_{(l)} \ → \ C_{6}H_{12}O_{6(s)} \ + \ 6O_{2(g)} \)

 

 

Cobalt chloride hydrate equilibrium

\(  [CoCl_{4}]^{2-} \ _{(aq)} \ (blue) \ + \ 6H_{2}O_{(l)} \ ⇌ \ [Co(H_{2}O)_{6}]^{2+} \ _{(aq)} \ (pink) \ + \ 4Cl^{-} \ _{(aq)} \)

 

 

Iron thiocyanate equilibrium

\( Fe^{3+} \ _{(aq)} \ \text{(pale yellow)} \ + \ SCN^{-} \ _{(aq)} \ ⇌ \ [FeSCN]^{2+} \ _{(aq)} \ \text{(deep red)} \)

 

Nitrogen dioxide equilibrium

\(  2NO_{2(g)} \ (brown) \ ⇌ \ N_{2}O_{4(g)} \ \text{(colourless)} \)

 

Dissolution equilibrium

A saturated solution of an ionic compound will be in dynamic equilibrium.

Example: \( CuSO_{4(aq)} \  ⇌ \ Cu^{2+} \ _(aq) \  + \ SO_{4^{2-} (aq) }\)

 

 

Precipitation reactions

A good knowledge of the solubility rules is essential to determining whether a precipitation reaction will occur when solutions containing ionic compounds are mixed.

Example:

Full formula equation: \( BaCl_{2(aq)} \ + \ Na_{2}SO_{4(aq)} \ → \ BaSO_{4(s)} \ + \ 2NaCl_{(aq)} \)

Net ionic equation: \( Ba^{2+} \ _{(aq)} \  + \ SO_{4^{2-} (aq)} \ → \ BaSO_{4(s)} \)

 

 

The most important formula for Chemistry success? 👇

 

Module 6: Acid/Base Reactions

Ionisation

1. Strong acids undergo complete ionisation in water

Example: \( HCl_{(aq)} \ + \ H_{2}O_{(l)} \ → \ H_{3}O^{+} \ _{(aq)} \  + \ Cl^{-} \ _{(aq)} \)

\( (HCl_{(aq)} \ → \ H^{+} \ _{(aq)} \ + \ Cl^{-} \ _{(aq)}) \)

 

2. Weak acids undergo partial ionisation in water

Example:  \( CH_{3}COOH_{(aq)} \ + \ H_{2}O_{(l)} \ ⇌ \ H_{3}O^{+} \ _{(aq)} \ + \ CH_{3}COO^{-} \ _{(aq)} \)

\( (CH_{3}COOH_{(aq)} \ ⇌ \ H^{+} \ _{(aq)} \  + \ CH_{3}COO^{-} \ _{(aq)}) \)

 

3. Strong bases undergo complete dissociation in water

Example: \( NaOH_{(aq)} \ → \ Na^{+} \ _{(aq)} \  + \ OH^{-} \ _{(aq)} \)

 

4. Weak bases undergo partial ionisation in water

Example: \( NH_{3(aq)} \  + \ H_{2}O_{(l)} \ ⇌ \ NH_{4^{+} (aq)} \  + \ OH^{-} \ _{(aq)} \)

 

Neutralisation

Word equation: acid + base → salt + water

Example: \( H_{2} \color{red}{SO_{4}} _{(aq)} \ + \ 2 \color{blue}{K} OH_{(aq)} \ → \ \color{blue}{K_{2}} \color{red}{SO_{4}} _{(aq)} \ + \ H_{2}O_{(l)} \)

 

 

Acids and carbonates

Word equation: acid + carbonate → salt + water + carbon dioxide

Example: \( 2H \color{red}{NO_{3}} _{(aq)} \ + \ \color{blue}{Na} _{2} CO_{3(s)} \ → \ 2 \color{blue}{Na} \color{red}{NO_{3}} _{(aq)} \ + \ H_{2}O_{(l)} \ + \ CO_{2(g)} \)

 

 

Acids and metals

Word equation: acid + metal → salt + hydrogen gas

Example: \( 2H \color{red}{Cl} _{(aq)} \ + \ \color{blue}{Mg} _{(s)} \ → \ \color{blue}{Mg} \color{red}{Cl} _{2(aq)} \ + \ H_{2(g)} \)

 

 

Acid and ammonia:

Word equation: acid + ammonia → ammonium salt

Example: \(  HCl_{(aq)} \ + \ NH_{3(aq)} \ → \ NH_{4}Cl_{(aq)} \)

 

 

Module 7: Organic Chemistry

Addition reactions of unsaturated hydrocarbons

 

Reactions of alcohols

 

Additional organic reactions

 

 

Combustion of hydrocarbons and alcohols

1. Complete combustion produces carbon dioxide and water.

Examples:

Hydrocarbon: \( C_{3}H_{8(g)} \ + \ 5O_{2(g)} \ → \ 3CO_{2(g)} \ + \ 4H_{2}O_{(l)} \)

Alcohol: \( C_{2}H_{5}OH_{(l)} \  + \ 3O_{2(g)} \ → \ 2CO_{2(g)} \ + \ 3H_{2}O_{(l)} \)

 

2. Incomplete combustion occurs when insufficient oxygen is present for a complete reaction to occur.

Water and carbon monoxide \((CO_{(g)})\) and/or soot \((C_{(s)})\) are produced in an incomplete combustion.

 

 

Fermentation

Fermentation of glucose: \( C_{6}H_{12}O_{6(aq)} \ → \ 2C_{2}H_{5}OH_{(l)} \ + \ 2CO_{2(g)} \)

Conditions for fermentation:

• Zymase (enzyme in yeast)
• Aqueous solution of sugar
• Anaerobic condition
• Typically 30–40 °C, but depends on yeast strain

 

 

Additional reactions that are good to know

Redox

1. Oxidation: \( M_{(s)} \ → \ M^{+} \ _{(aq)} \ + \ e^{-} \)

 

2. Reduction: \( M^{+} \ _{(aq)} \ + \ e^{-} \ → \ M_{(s)} \)

 

3. Redox equation: Combine oxidation and reduction equations and balance electrons.

Example

• Oxidation: \( Cu(s) → Cu2+(aq) + 2e- \)
• Reduction:  \( Ag+(aq)  + e- → Ag(s) \)
• \(1:2 \) for \(  Cu:Ag \), so combine with 2x reduction equation
• \( Cu_{(s)} \ + \ 2Ag^{+} \ _{(aq)} \  + \ 2e^{-} \ → \ Cu^{2+} \ _{(aq)} \ + \ 2e^{-} \ + \ 2Ag_{(s)} \)
• Cancel the electrons: \(  Cu_{(s)} \ + \ 2Ag^{+} _{(aq)} \ → \ Cu^{2+} \ _{(aq)} \ + \ 2Ag_{(s)} \)

 

4. Limewater test:  \( Ca(OH)_{2(aq)} \ +  \ CO_{2(g)} \ → \ CaCO_{3(s)} \ + \ H_{2}O_{(l)} \)