Chemistry- acid, bases, making salts

• Litmus acids alkalis


  Acid - red

  Alkali - blue

  Neutral - purple
• Phenolphthalein in acid and alkali

  Acid - colorless

  Alkali - pink

  Neutral - colorless
• Methyl orange in acid and alkali

  Acid - red

  Alkali -yellow

  Neutral - orange
• Ph scale


  1-3 - highly acidic

  4-6 - weakly acidic

  7 - neutral

  8-10 - weakly alkaline

  11-14 - strongly alkaline
• Universal indicator


  Acidic - red

  Neutral - green

  Alkali - blue
• What are acids in an aqueous solution a source of

  Hydrogen ions
• What are alkalis in an aqueous solution a source of

  Hydroxide ions
• What do alkalis do to acids

  Alkalis neutralise acids
• Acids and bases in terms of proton transfer


  acids are proton donors and bases are proton acceptors, a proton is a hydrogen ion
• Example of this hydrogen chloride + ammonia


  Hcl + NH3 - NH4 + Cl, Hcl is an acid and it donates the hydrogen (proton) to the base, proton donor to acceptor
• What happens when metal and acid


  Metal + acid - salt + hydrogen
• What happens when acid and metal oxide


  Acid + metal oxide - salt + water
• What happens when acid and metal carbonate


  Metal carbonate + acid - salt + water + co2
• Nitric acid


  HNO3
• Hydrochloric acid


  HCl
• Sulfuric acid


  H2SO4
• Nitric acid + sodium carbonate salt formed


  Sodium nitrate
• Hydrochloric acid + Sodium carbonate


  Sodium chloride
• Sulfuric acid + sodium carbonate


  Sodium sulfate
• Nitric acid + magnesium


  Magnesium nitrate
• Hydrochloric acid + magnesium


  Magnesium chloride
• Sulfuric acid + magnesium


  Magnesium sulfate
• Nitric acid + potassium oxide


  Potassium nitrate
• Hydrochloric acid + potassium oxide

  Potassium chloride
• Sulfuric acid + potassium oxide

  Potassium sulfate
• Nitric acid + copper hydroxide

  Copper nitrate
• Hydrochloric acid + copper hydroxide

  Copper chloride
• Sulfuric acid + copper hydroxide

  Copper sulfate
• Nitric acid + ammonia

  ammonium nitrate
• Hydrochloric acid + ammonia

  Ammonium chloride
• Sulfuric acid + ammonia

  Ammonium sulfate
• What acts as a base


  Metal oxides, metal hydroxides, ammonia
• What acts as a base that is soluble in water

  Alkali
• Describe an experiment to prepare a pure dry sample of a soluble salt starting from an insoluble reactant

  Add insoluble base to acid until it stops reacting (warm the acid, stir salt to help dissolving

  Filter to remove excess base from salt solution

  Heat salt solution to remove some of the water

  Leave salt solution to cool and crystallise

  Collect salt crystals by filtration

  Dry crystal on paper towel/filter paper
• Practical: Prepare a sample of pure, dry hydrated Copper (II) Sulfate Crystals starting from Copper (II) Oxide (method and explain)

  Heat acid Sulfuric acid in a beaker - to speed up rate of reaction

  Add base copper oxide until in excess and stir with glass rod - to neutralise all the acid

  Filter the mixture using filter paper and funnel - removes any excess copper oxide

  Gently heat the filtered solution (copper sulfate) - to evaporate some of the water

  Until crystals form on a glass rod - shows a hot saturated solution formed

  Leave to cool and crystallise

  Remove the crystals by filtration - to remove crystals

  Dry by leaving in a warm place - evaporates the water
• Practical - prepare a sample of pure dry lead II sulfate


  Mix similar volumes lead nitrate solution and sodium sulfate solution in a beaker

  The precise volumes do not matter since any excess will be removed later

  A white precipitate of lead II sulfate will form

  The reaction mixture is filtered

  The residue left on the filter paper is washed with distilled water several times to remove impurities

  The residue is then moved to a warm oven to dry
• Rules for solubility


  common sodium, potassium and ammonium compounds are soluble

  • all nitrates are soluble

  • common chlorides are soluble, except those of silver and lead(II)

  • common sulfates are soluble, except for those of barium, calcium and lead(II)

  • common carbonates are insoluble, except for those of sodium, potassium and

  ammonium

  • common hydroxides are insoluble except for those of sodium, potassium and

  calcium (calcium hydroxide is slightly soluble).
• How to make insoluble salts

  Mix solutions together to form insoluble salt - precipitate will form

  Filter to collect insoluble salt

  Wash insoluble salt to remove any unreacted solution

  Dry the insoluble salt
• Crystallisation


  Gently heat solution in evaporating basin to evaporate some of the water

  Until crystals form on glass rod (proving hot saturated solution has formed)

  Leave to cool and crystallise

  Filter to remove the crystals

  Dry by leaving in a warm place