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Volumetric Analysis2
Volumetric Analysis: Oxidation-Reduction
Question | Answer |
---|---|
Why is our main Oxidising Agent Potassium Permanganate not considered a primary standard? | It cannot be found in a pure enough state and decomposed in sunlight |
Opposing reducing agent used for Potassium Permanganate? | Sulphuric Acid |
Why can we not use Hydrochloric Acid or Nitric Acid in our experiments with Potassium Permanganate? | They are oxidising agents, not reducing agents! |
Indicator used with Potassium Permanganate? Colour change? | Potassium Permanganate is its own indicator. It goes from purple to colourless. |
Besides being our reducing agent there is a second reason for adding Sulphuric acid to this titration involving Potassium Permanganate. What is it? | Potassium Permanganate will only change colour in an acidic solution, it will not work in a neutral or basic environent. |
Why is Iron Sulphate not considered a primary standard? | It is oxidised in air and reacts with water (hydrolysis) |
What compound provides us with a pure source of Iron Sulphate? | Ammonium Iron (II) Sulphate |
How do we prevent the Ammonium Iron (II) Sulphate from reacting with the water when dissolved? | Addition of Sulphuric Acid supplies H+ ions to the solution which prevents Hydrolysis. |
What is the ration between Fe+2 ions and Potassium Permanganate | 1:5 |
What illness is caused by lack or Iron in our diet? | Anaemia |
What is the function of iron in our diet? | It is an essential part of haemoglobin, the molecule that carries oxygen in our blood. |
Symptoms of anaemia? | Fatigue, weakness and pale skin |
One use of sodium thiosulphate in industry? | Used in the development of photographs. |
Why is Sodium Thiosulphate not considered a primary standard? | It is not found in a 100% pure state |
Why is Iodine not considered a primary standard? How do we supply pure Iodine to our titrations? | Iodine sublimes at room temperature. Excess Iodine is supplied by the addition of Potassium Iodide. |
What indicator is used when titrating Potassium Permanganate and Sodium Thiosulphate? When is the indicator added? | Starch indicator added. It is added when a straw yellow colour appears. We continue the titration until the colour changes from blue/black to colourless. |
What colour appears when the Potassium Permanganate and Potassium Iodide are mixed together. What causes this colour? | Purple to red-brown as pure Iodine is released from the Potassium Iodide |
Why is the bleach solution diluted with water? | The bleach is a concentrated solution which would require too much reagents for the titration |