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20 Cards in this Set
- Front
- Back
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What is an acid-alkali neutralisation reaction? |
When hydrogen ions from the acid react with hydroxide ions from the alkali to form water |
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What colour is methyl orange in alkali? |
Yellow |
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What colour is methyl orange in acid? |
Pink-red |
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What colour is seen in a conical flask(end point) for methyl orange? |
Orange |
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What colour is phenolphthalein in alkali? |
Pink |
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What colour is phenolphthalein in acid? |
Colourless |
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What colour is seen in a conical flask(end point) for phenolphthalein? |
-Colourless if acid is added from burette -First tinge of pink if alkali is added from burette |
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Why is a burette used to measure the volume of one of the solutions instead of a measuring |
The diameter of the burette is small so the markings can be separated apart more on the burette for us to make a better reading of the volume. |
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Why is it necessary to rinse the burette and pipette with the solutions they will contain before filling them? |
Contaminants could be introduced if equipment not washed properly which could effect the concentration of the titrant and the reaction |
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Why is it necessary to use an indicator in the titration? |
An indicator changes colour depending on the properties of the substance it is added to. |
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Why is universal indicator not suitable to use in a titration? |
There is no sharp colour change |
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Why is a white tile used? |
COME BACK TO THIS |
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Why is it important to swirl the conical flask during the titration? |
To even out concentrations |
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What is meant by the end point? |
The colour seen in the conical flask |
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Why do you repeat the titration? |
To get concordant results |
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What are concordant results? |
2 consistent titration within 0.10cm3 |
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Which results are included in the calculation when you determine the mean or average titre? |
Run 1 and 3 (Ignore trial and run 2) |
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What safety precautions should you take when carrying out this experiment and why? |
-Wear gloves to prevent contact with skin -goggles to prevent contact with eyes |
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Why do you repeat the experiment without indicator? |
The salt crystals wouldn’t be pure as they’d be contaminated with indicator |
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What are the steps for titration? |
-Rinse pipette with alkali and burette with acid -Measure alkali using a pipette into a suitable container e.g a flask and then place flask on white tile -Add a few drops of indicator e.g. methyl orange -Fill burette with acid and read volume of acid in burette -Add acid from the burette to the flask, swirling slowly until indicator changes colour e.g. methyl orange from yellow to orange-peach -Read volume of acid in burette after titration -Repeat experiment until concordant results and without indicator present but using the same volumes -Heat gently to partially evaporate water until a saturated solution is formed-observed when first crystals appear -Allow to cool and crystallise -Filter -Dry crystals using absorbent paper |
