Chapter 13:Acids and Bases

Properties of acids

• Acid: any substance that releases hydrogen ions, H+, in aqueous solution
  • [ ] Aqueous solutions of acids are electrolytes,
• Acids have a sour taste
  • [ ] Example: Lemons, vinegar, and sour candies all contain acids.
• Acids change the color of certain acid-base indicates.
• Acids react with active metals to yield hydrogen gas.
• Acids react with bases to produce a salt compound and water.
• Turn blue litmus red
• Turn methyl orange red
• Turns Phenolphthalein colourless
• TiUniversal indicator Red /orange
• Contains PH-level below 7

Organic acid

• Organic Acid : found in natural products such as plants and animals.
  • [ ] They are sour to taste.
  • [ ] These acids are relatively harmless.( For example), they are not corrosive etc.
  • [ ] Example of some common organic acids: Ethanoic acid, citric acid, lactic acid.

Inorganic acid

• Inorganic acids: are corrosive, they have a sour taste and turn blue litmus red.
  • [ ] Hydrochloric acid
  • [ ] Sulphuric acid
  • [ ] Nitric acid

Weak and strong acid

• Strong acid which is completely ionized in an aqueous solution.

  • [ ] Eg: Hydrogen chloride (HCl), sulphuric acid, nitric acid.

• Weak acid which partially ionises in an acquous solution.

• [ ] Eg:carbonic, ethanoic , sulphurous, citric , carbonic.

Bases

• Bases: form a class of chemical substances which include all metal oxides and hydroxides.
  • [ ] A soluble base is called an 'alkali' an in aqueous solution, it produces hydroxide ion (OH-)

Properties of Bases

• Proton acceptors
  • [ ] as they contain hydroxide ions
• PH greater than 7
• Bitter taste
• Bases effect indicators
• Turn red litmus Blue
• Phenolphthalein turns purple/pink
• Universal indicator Blue
• Methyl orange YELLOW
• Slippery solutions
• Bases neutralise acids
• React with acids to form salt and water
• Examples of bases: Sodium hydroxide, potassium hydroxide, acqeuous ammonia, calcium hydroxide, magnesium oxide, copper (II) oxide.

Reactions

• Metal and acid➡️ salt and hydrogen

• [ ] Eg: zinc + sulphuric acid➡️ zinc sulphate+ Hydrogen

• Metal oxide + acid ➡️ salt and water

• [ ] Eg: Copper(II) oxide + sulphuric acid➡️ copper sulphate+ water

• Metal hydroxide + acid ➡️salt and water

• [ ] Eg: Potassium hydroxide+ hydrochloric acid ➡️ potassium chloride + water

• Metal carbonate + acid ➡️salt+water+ carbon dioxide

• [ ] Eg: Zinc carbonate+ nitric acid ➡️ zinc nitrate +water+ carbon dioxide

Oxides

• Basic oxides :solid metal oxides, some of which dissolve in water to form alkalis
• Acidic oxides :non-metal oxides, which dissolve in water to form acids
• Neutral oxides :non-metal oxides which are usually insoluble in water and have neither acidic nor basic properties
• Amphoteric oxides : metal oxides which can react with both acids and alkalis to form salts and water.