9.1 Common acids and alkalis

◦ remove stains in toilet bowls | ***Remove grease*** 

• cleaning agents

• NH3: kitchen/ glass cleaners ◦ remove grease

• NaOH: drain cleaners ◦ release heat ◦ remove grease/ hair | | Industrial chemicals • H₂SO₄: fertilizers, dyes, paints | Industrial chemicals  • KOH: batteries | | Preservatives • Ethanoic acid (Vinegar) • kill microorganisms (cannot grow/ reproduce) | | | • Body lotion • Hair conditioner • Toilet cleaner • Apples • Lemon/ Orange/ Grapefruit | • Baking soda • Glass cleaner • Kitchen cleaner • Soap • Toothpaste |

Safety precautions

2. Wear safety goggles/ protective gloves
3. Waste bottles
4. Wash hands | 1. Taste
5. Mix with other chemicals |

Measures

1. Wash the affected area under slow running water for at least 10 minutes
2. Remove contaminated clothings and avoid making contact with the chemical
3. Wash eyes with eye wash bottle for at least 10 minutes
4. Call ambulance for serious injuries

9.2 Acid- alkali indicators and pH scale

Indicators - show presence of acids and alkalis

| Natural indicators | • Pigments: change colour in the presence of acid or alkali ◦ rose ◦ blueberry/ strawberry ◦ beetroot/ onion | | --- | --- | | Litmus | • solution/ paper ◦ Blue: Alkaline ◦ Red: Acidic ◦ No change: Neutral |

Universal indicator and pH scale

| Universal indicator | • mixture of several indicators ◦ shows a range of different colors on degrees of acidity and alkalinity | | --- | --- | | pH paper | • paper form of universal indicator | | pH scale | • each color corresponds to a pH value ◦ less than 7: acidic ◦ equal to 7: neutral ◦ greater than 7: alkaline |

Electronic instruments

| pH meter | • a probe connected to digital display • accurate to two decimal places | | --- | --- | | pH sensor connected with a data-logger | • monitor changes |

9.3 Neutralization