Acids and salts chemistry

• Universal indicator


  Red in acid, green at neutral, blue/dark blue in alkali
• Litmus indicator


  Red in acid, blue in alkali
• Phenolphthalein indicator


  Colourless in acid, pink in alkali
• methyl orange indicator


  Red in acid, orange at neutral, yellow in alkali
• What are indicators used for


  Indicators have specific colours in acids and alkalis so we can use them to determine if a substance is acid or alkali
• What does the PH scale run from and whats it for

  0-14 tells me if a substance is acid or alkali
• Red on the PH scale


  strong acid eg. hydrochloric
• orange on the PH scale


  acid
• yellow on the ph scale


  weak acid eg. ethanoic (vinegar)
• green on the ph scale


  neutral (7)
• blue on the ph scale


  weak alkali eg. ammonia
• purple on the ph scale


  strong alkali eg. sodium hydroxide
• What is an acid


  A source of hydrogen ions (H+) when dissolved in water
• acids + metal


  -> salt + hydrogen
• What makes an acid behave like an acid


  the presence of H+
• What is an alkali


  a source of hydroxide ions (OH-) ions when dissolved in water
• What happens when an acid reacts with an alkali


  We say a neutralisation reaction occurs because they are pos + neg so they cancel eachother out
• acid + alkali


  -> salt + water
• acid + base


  -> salt + water
• An acid is a proton donor (giver)
• An base is a proton acceptor
• acid + metal carbonate


  -> salt + carbon dioxide + water
• sodium oxide + hydrochloric acid


  -> sodium chloride + water
• zinc + nitric acid


  -> zinc nitrate + hydrogen
• What is a base


  A substance that can accept H+ ions (protons) in water and can neutralize an acid and produce a salt
• If a substance is soluble it can be dissolved in liquid
• If a substance is insoluble it cannot be dissolved in liquid.
• Preparation of a soluble salt using the excess base method (preparing copper (ll) sulphate by reacting sulphuric acid with an excess of insoluble copper (ll) oxide)


  1. Heat 15ml of sulphuric acid so the reaction can happen quicker in warm water from the ketlle with an excess of copper (ll) oxide in so that all the acid can react and only copper (ll) oxide is left

  2. Filter the mixture using filter paper into a conical flask. This is because copper (ll) oxide is insoluble in water

  3. Heat the solution in the conical flask using a bunsen burner until it boils. It was heated to evaporate some water

  4. Pour the liquid into the petri dish and wait for crystals to form. Crystals form because the solute is less soluble at a lower temperature
• copper (ll) oxide + sulphuric acid 


  -> copper (ll) sulphate + water
• what is a solute


  a substance that can be dissolved to make a solution by a solvent
• what is a solvent


  a substance in which a solute is dissolved to make a solution
• what is a solution


  when a solute is dissolved in a solvent
• solvent + solute


  = solution
• what is a saturated solution


  a substance that has dissolved as much solute as it is capable of dissolving
• how can we dissolve more solute


  by increasing the temperature
• the solubility of a substance increases as the temperature increases
• if we cool down a saturated solution, some solid will "undissolve" or crystalise
• what is solubility


  the measurement of the maximum mass of a substance which will dissolve in 100g of water at a given temperature
• solubility decreases as you cool down. no more solute can be dissolved at a lower temperature causing the solute to seperate from the solution
• how to indentify positive ions


  1. clean a nichrome wire with hydrochloric acid 2.dip wire in substance to be tested 3. hold wire in roaring bunsen flame 4. observe colour