Indicators

Colour Change

Acids

— corrosive → eats away things

— weak, even when concentrated

acid → litmus = purple → red

Common Acids

• Hydrochloric Acid - HCl (aq)
• Sulfuric Acid - H2SO4 (aq)
• Nitric Acid - HNO3 (aq)
• Ethanoic Acid - CH3COOH (aq)

Alkalis

— needs to be handled with care

alkali → litmus = purple → blue

Common Alkalis

• Sodium Hydroxide - NaOH (aq)
• Potassium Hydroxide - KOH (aq)
• Calcium Hydroxide - Ca(OH)2
• Ammonia - NH3 (aq)

pH Scale

— 1 - 14

— <7 → acidic, the lower you go

— >7 → basic, the higher you go

— 7 = neutral

Strong Acids vs. Weak acids

— strong acids ⇒ lower pH level + better conductor

• in strong acid solutions → 100% of the molecules become ions when dissolved in water
• more ions ⇒ more H+ ions which defines an acid ⇒ more acidic
• → a better conductor (more free moving ions)

— weak acids ⇒ higher pH level + a poor conductor

• in weak acid solutions → not 100% of the molecules become ions
• less ions ⇒ less H+ ions ⇒ less acidic
• a poor conductor (less free moving ions)

Strong bases vs. Weak acids

— strong bases ⇒ lower higher pH level + better conductor

• 100% of the solution is ions
• more ions ⇒ OH- ions which defines an acid ⇒ more basic
• better conductor (more free moving ions)

— weak bases ⇒ lower pH level + a poor conductor

• not 100% of the solution is ions
• less ions ⇒ OH- ions ⇒ less basic
• a poor conductor (less free moving ions)

Typical Acid Reactions

— acid + metal → hydrogen + salt

— H2 in the acid gets displaced → salt is formed + hydrogen is formed

— redox reaction → e.g. Mg + H2SO4 → MgSO4 + H2

                               0                           +II