Topic 4 - C4

• What pH is acidic?


  0-6
• What pH is alkali?


  8-14
• What pH is neutral?


  7
• What colour is acid?

  red/orange/yellow
• What colour is alkali?

  blue/purple
• What colour is neutral?


  green
• What is an acid?

  a substance that forms aqueous solutions with pH of less than 7
• What ions do acids from with water?


  H+
• What is a base?


  a substance with a pH greater than 7
• What is an alkali?


  a base that dissolves in water to form a solutions with a pH greater than 7
• What ions do alkalis form with water?


  OH-
• what is the reaction between acids and bases called?


  neutralisation
• What is the equation for neutralisation?


  acid + base -> salt + water
• Titration practical

  1. using a pipette and pipette filler as set volume of alkali to conical flask (usually 25cm³) and add indicator (2 or 3 drops)
  2. use funnel to fill a burette with some acid of known concentration, do this below eye level to prevent acid spillages
  3. record initial volume of acid in burette
  4. using burette add the acid to alkali a bit at a time, swirl the conical flask
  5. the indicator changes colour when all the alkali has been neutralised
  6. recored final volume and calculate using initial volume to calculate volume of acid to neutralise alkali
• What is universal indicator used for?


  estimate pH of solution by turning a range of colours
• What colours does litmus paper go?


  • acid - red

  • alkali - blue
• What colours does phenolphthalein go?


  • acid - colourless

  • alkali - pink
• What colours does methyl orange go?


  • acid - red

  • alkali - yellow
• What makes a strong acid?


  ionises completely in water and dissociate to release H+ ions
• What is pH?


  concentration of H+ ions
• What kind of reactions is weak acid?

  reversible
• What does a weak acid try to make equilibrium with?


  undissociated and dissociated acid particles
• What are metal oxides and metal hydroxides examples of?


  bases
• What is metal carbonate an example of?


  base
• What does metal carbonate react with and what are the products?


  acid + metal carbonate -> salt + water + carbon dioxide
• Making soluble salts using insoluble bases - practical

  1. need to pick right acid and insoluble base (e.g. hydrochloric acid + copper oxide)
  2. gently warm dilute acid with bunsen burner
  3. take off heat and add insoluble base in excess so its all reacted
  4. filter excess to get salt solution
  5. use crystallisation: heat solution until some is evaporated then let it cool to form crystals
• What is the order of reactivity in metals? (most to least)


  potassium, sodium, lithium, calcium, magnesium, carbon, zinc, iron, hydrogen, copper
• What is the equation for an acid reacting with a metal?


  acid + metal -> salt + hydrogen
• What is the equation when metal reacts with water?


  metal + water -> metal hydroxide + hydrogen
• What is oxidation?


  Is the gaining of oxygen (when reacting metals with oxygen)
• What is reduction?


  Is the loss of oxygen (when reacting metals with oxygen)
• How else can metals be extracted? 


  Reduction with carbon
• Example of extraction by reduction using carbon:

  iron (III) oxide + carbon -> iron + carbon dioxide

  ~ ore (iron) is reduced as oxygen is removed from it

  ~ carbon is oxidised as oxygen is added to it
• How do you know if you can extract by reduction with carbon?

  Has to be less reactive then carbon (zinc, iron, copper)
• How are metals higher then carbon on the reactivity table extracted?

  electrolysis
• What is a redox reaction?

  where one substance is oxidised and another is reduced (in terms of electrons)
• What is a loss of electrons called?

  oxidation
• What is a gain of electrons called?

  Reduction
• How do you remember if its oxidation or reduction (in terms of electrons)?

  O - oxidation

  I - is

  L -loss

  R - reduction

  I - is

  G - gain
• How do you remember if a reaction is a redox reaction (only for electrons)?


  Reduction (RED) + oxidation (OX) = REDOX