topic 4

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• potassium, sodium, lithium, calcium, magnesium, carbon, zinc, iron, hydrogen, copper
• indicators change colour depending on how strong the pH is
• a pH probe is attached to a pH meter to give a numerical value for pH
• acids form H+ ions in water
• a base is a substance that reacts with an acid to form a salt
• alkali will form OH- ions in water
• a neutralisation reaction occurs between an acid and a base to form water and a salt
• a titration allows us to find the exact volume of acid needed to neutralise a measured volume of an alkali
• titration reaction

  1. using a pipette and a pipette filter add a set volume of alkali into a conical flask
  2. add 2-3 drops of indicator into alkali
  3. fill burette with acid of known concentration
  4. record initial volume of acid
  5. slowly add acid into conical flask and gently stir
  6. when instant colour change neutralisation has occurred
  7. stop adding acid and record final volume of acid to calculate the amount used
• while carrying out a titration reaction you should do a rough titration first to get a rough idea of when the solution changes
• while carrying out a titration reaction you should repeat the experiment until you get results of within 0.1 of each other
• a universal indicator has a variety of colours
• in titrations you need a single indicator to see immediate colour change for neutralisation
• single indicators are

  1. phenolphthalein
  2. methyl orange
  3. litmus
• phenolphthalein is colourless in an acid and pink in an alkali
• methyl orange is red in acid and yellow in alkali
• litmus in red in an acid and blue in an alkali
• strong acids fully ionise in water
• weak acids only partially ionise in water, as its a reversible reaction so it sets up a point of equilibrium between the dissociated and undissociated particles
• the pH of an acid or alkali is a measure of the concentration of H+ ions in that solution
• acid strength is the proportion of acid molecules that ionise in water
• concentration is how much is is a given volume
• nitric acid creates a nitrate
• sulfuric acid creates a sulfate
• hydrochloric acid creates a chloride
• acid + metal oxide -> salt + water
• acid + metal carbonate -> salt + water + carbon dioxide
• more reactive metals have a faster reaction
• the speed of a reaction indicates the rate of hydrogen bubbles given off
• most metals are not found in pure forms and are usually found as compounds so need extracting
• reactions that separate oxides from metals in a reduction reaction
• reactions where oxides are added to metals is oxidation
• reduction with carbon depends on where it is in the reactivity series
• elements below carbon in the reactivity series can be extracted using carbon
• elements above carbon in the reactivity series can be extracted using electrolysis
• redox reactions happen if electrons are transferred
• in electrolysis oxidation is the loss of electrons
• in electrolysis reduction is gain of electrons
• electrolyte has to be molten or dissolved ionic compound