Antacids and Group 2 Metals: AQA A-Level Chemistry Guide
Learn the chemistry of antacids and Group 2 metal compounds. Covers magnesium and calcium reactions, agricultural lime, and soil pH management.
Antacids and Group 2 Metals
AQA A-Level Chemistry Summary
Magnesium-Based Antacids
Magnesium hydroxide, Mg(OH)₂ (milk of magnesia)
Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O
Low solubility → slow, controlled neutralisation
Magnesium ions are safe and naturally present
Side effect: laxative effect if overused
Calcium-Based Antacids
Main component: Calcium carbonate (CaCO₃)
Neutralisation reaction: <br>CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O
Provides additional calcium for bone health
Produces CO₂ which may cause bloating
Why Group 2 Metals Are Used
Form M²⁺ ions
Less soluble than Group 1 compounds
Prevent over-neutralisation of stomach acid
Safer than strong alkalis (e.g. NaOH)
Key Chemistry Links
Hydroxides = bases
Carbonates + acids → salt + CO₂ + H₂O
Low solubility = controlled pharmaceutical action
Beyond A-Level
Many antacids combine Mg²⁺ and Ca²⁺ compounds to balance side effects
Pharmaceutical design focuses on buffering stomach pH, not full neutralisation
Uses of Group 2 Compounds in Farming
Improving soil quality, plant growth, and animal health
Calcium Compounds
Agricultural Lime
Calcium carbonate (CaCO₃) applied as powdered limestone
CaCO₃ + 2H⁺ → Ca²⁺ + CO₂ + H₂O
Reacts to neutralise acidic soil (H⁺ ions) effectively
Essential for nutrient absorption and preventing crop failure
Soil Treatment
Spreading crushed lime to adjust pH
Magnesium in Farming
Sources: Magnesium carbonate (MgCO₃) and Dolomite
CaCO₃ · MgCO₃
Mg²⁺ is the central ion in chlorophyll (essential for photosynthesis)
Prevents chlorosis (yellowing of leaves between veins)
MgCO₃ neutralises soil acidity, improving nutrient uptake
Fertilisers & Animal Farming
Fertilisers replenish key nutrients (N, P, K)
Calcium vital for eggshells & bone reinforcement
Magnesium prevents grass tetany in livestock
Balances pH to optimise growth & health
AQA Chemistry Links
Why Group 2 Compounds are Suitable
M²⁺ ions effectively neutralize excess stomach acid
Low solubility prevents high alkalinity & tissue damage
Slow reaction rates ensure controlled, long-lasting relief
- chemistry
- a-level-chemistry
- antacids
- group-2-metals
- magnesium-hydroxide
- calcium-carbonate
- farming-chemistry
- inorganic-chemistry