titrations

• Give a well known example of an acid used in titrations

  HCL (hydrochloric acid)
• Give a well known example of a base used in titrations

  NaOH (sodium hydroxide)
• Equation for when NaOH reacts with HCl?

  HCl + NaOH --> NaCl + H2O
• What tall, thin piece of apparatus do we keep the acid in during an acid-base titration?

  burette

  
• In what piece of apparatus does the titration reaction occur in?

  Conical flask

  
• When we have the acid in the burette, what two things do we know about it? (2)

  - concentration (we are told this by the lab technician or in the question)

  
  

  - volume added to base
• How do we measure the volume of acid added to the base during a titration?

  Measure the initial volume of acid in the burette

  
  

  When the reaction is completed, remeasure the volume of the acid in the burette

  
  

  The difference is the volume of acid added to the base
• What do we use to wash out the conical flask before the titration?

  Wash out with distilled water
• What do we know about the base in the conical flask before the titration?

  The volume
• How do we know the volume of the base in the conical flask?

  We use a pipette to accurately transfer a known volume of base into the conical flask
• Equation for concentration?

  Concentration = moles/ volume
• What are we trying to find out during a titration?

  The concentration of the base
• How do we find the concentration of the base? (3)

  Find moles of acid reacted with base by multiplying volume used of acid (in dm3) by concentration.

  
  

  At end point, Moles of acid = moles of base

  
  

  Divide moles of base (which is moles of acid) by volume (given by pipette)
• 1000cm3 is what in dm3

  1dm3
• 10,000cm3 is what in dm3?

  10dm3
• 0.8dm3 is what in cm3

  800cm3
• When measuring volumes in a burette, where do we measure?

  From the bottom of the meniscus

  
• What is the 'tap' called in a burette?

  stopcock
• How do we add acid into the burette?

  By pouring through a funnel
• What is an indicator


  An indicator is a substance which changes colour depending on the pH conditions of the mixture.
• Why do we use indicators during titrations?

  to show when the end point of the reaction has occurred (i.e. when the neutralisation has occurred)
• Name a common indicator used in titrations?

  methyl orange
• What is the colour change at the end point of the reaction using methyl orange?

  Red to yellow
• Definition of a strong acid? (please learn)

  A substance that completely dissociates releasing H+ in water
• Definition of a weak acid? (please learn)

  A substance that partially dissociates releasing H+ in water
• Definition of a strong base (please learn)

  A substance that fully dissociates releasing OH- in water
• Definition of a weak base (please learn)

  A substance that partially dissociates releasing OH- in water
• Is a substance an acid, base or neutral if pH>7

  base (= alkali)
• Is a substance an acid, base or neutral if pH<7

  acid
• Is a substance an acid, base or neutral if pH=7

  neutral
• what is the moles equation using mass and mr?

  moles = mass/mr