Acids, Bases & Protons (Edexcel IGCSE Chemistry)

Proton transfer

• The earlier definition of an acid and a base can be extended
• In terms of proton transfer, we can further define each substance in how they interact with protons

Acids

• Acids are proton donors as they ionize in solution producing protons, H⁺ ions
• These H⁺ ions make the aqueous solution acidic

• Example: hydrochloric acid

HCl (aq)   →    H⁺ (aq)    +    Cl^– (aq)

Bases (Alkalis)

• Bases (alkalis) are proton acceptors as they ionize in solution producing OH^- ions which can accept protons
• These OH^- ions make the aqueous solution alkaline
• Example: sodium hydroxide

NaOH (s)   →    Na⁺ (aq)    +    OH^– (aq)