IS 2nd UT

• Acids


  • Strong: Hydrochloric acid, Sulphuric acid, Nitric acid
  • Weak: Carbonic acid(soft drinks), Citric acid(oranges/lemons), Ethanoic acid(vinegar)
• Products containing acids


  • Lotion, toilet cleaner, shampoo
• Alkalis


  • Strong: Sodium hydroxide solution, Calcium hydroxide solution(lime water), Ammonia solution
• Products containing alkalis


  • Glass cleaner, kitchen cleaner, baking soda, toothpaste, rice dumpling, noodles
• Acids and alkalis


  • Irritant and corrosive (may burn skin and eyes)
• Handling acids and alkalis

  1. Read hazard warning symbols

  2. Wear spectacles, laboratory coat, disposable gloves

  3. Never taste

  4. Don't fill more than one-third of container

  5. Don't mix without teacher approval

  6. Pour waste into suitable bottles, not sink

  7. Wash hands after handling
• First aid for acid/alkali exposure

  1. Keep calm, report to teacher

  2. Wash affected area under running water for at least 10 mins

  3. Wash eyes with eye bottle immediately

  4. Carefully remove contaminated clothes
• Natural indicator


  Pigments show different colors in different solutions
• Litmus/Litmus paper


  Acids: red, Alkalis: blue, Neutral: no observable change
• Universal indicator & pH paper

  pH values indicate relative acidity/alkalinity (1-6: acidic, 7: neutral, 8-14: alkaline)
• pH meter and data logger


  More accurate and precise, suitable for solutions of any color
• Acid + alkali


  Neutralize each other to form salt (white precipitate) and water
• Neutralization reactions


  • Sodium hydroxide + hydrochloric acid → sodium chloride + water
  • Potassium hydroxide + nitric acid → potassium nitrate + water
  • Sodium hydroxide + sulphuric acid → sodium sulphate + water
• The mass of reactants and products is conserved in neutralization
• Brushing teeth with toothpaste

  Slightly alkaline toothpaste neutralizes acids produced by bacteria, preventing tooth decay
• Treating stomach ache with antacid

  Alkaline antacid neutralizes excess acid in stomach, relieving stomach ache
• Regulating soil pH


  Adding alkaline lime to soil neutralizes acids in soil
• Treating insect stings and bites

  Wasp stings (alkaline) neutralized by acidic vinegar, ant bites (acidic) neutralized by alkaline baking soda
• Treating chemical waste


  Neutralizing acids/alkalis in waste reduces water pollution
• Reaction between dilute acids and metals


  Metal + acid → salt + hydrogen
• Reactions between dilute acids and metals

  • Zinc + hydrochloric acid → zinc chloride + hydrogen
  • Iron + sulphuric acid → iron sulphate + hydrogen
• Reaction between dilute acids and carbonates

  Carbonate + acid → salt + water + carbon dioxide
• Reactions between dilute acids and carbonates

  • Calcium carbonate + hydrochloric acid → Calcium chloride + water + carbon dioxide
  • Magnesium carbonate + sulphuric acid → magnesium sulphate + water + carbon dioxide
• Acid rain


  pH value lower than 5.6
• Cause of acid rain

  Burning of fossil fuels releases acidic gases like sulphur dioxide and nitrogen oxides, which form sulphuric acid and nitric acid in the air
• Effects of acid rain


  • Corroding metal objects and building materials
  • Killing living things in water
  • Damaging plants
• Concentrated acids and alkalis


  • Highly corrosive, can cause great harm to the body
• Potential dangers in handling acids and alkalis

  • Toilet cleaners contain acids, glass/kitchen cleaners contain alkali
  • Mixing products may cause reactions, heat, spills, and toxic products
  • Read safety instructions, keep room ventilated, wear protective equipment, wash hands thoroughly
• First aid for acid/alkali exposure accidents

  1. Wash affected area with large amount of running water

  2. Move injured person to fresh air

  3. Seek medical attention as soon as possible