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EMPA Questions
AQA Chem EMPA
20
Chemistry
12th Grade
05/12/2015

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Cards

Term
What can be added to sulphate ions to test for them? What would be observed?
Definition
BaCl2
White precipitate formed
Term
What can be used to test for ammonia? What would be observed?
Definition
Damp litmus paper
Colour change from red to blue
Term
What precipitate is formed and what is the colour of it when NaOH is added to Iron (II) chloride?
Definition
Fe(H2O)4(OH)2
Green
Term
How could a test to time the colour change of a solution be improved from looking at the solution in a flask?
Definition
-Keep the solution at a constant temp because reaction rate is influenced by temp
-Use a colorimeter to monitor colour change which gives a more accurate time of colour change
Term
How could H2O2 be separated from Ba(NO3)2?
Definition
By fractional distillation
Term
Why would it be better to react sulphuric acid with BaO2 rather than nitric acid?
Definition
BaSO4 is insoluble so easier to separate from H2O2
Term
Why can't infrared spectroscopy be used to identify H2O in a solution of H2O2?
Definition
They both contain an OH group
Term
Why does hydrogen peroxide decompose more quickly if it is kept in a clear glass bottle rather than a brown one?
Definition
Decomposition is accelerated by light
Term
Even if hydrogen peroxide is corrosive, why does a spillage not have long term effects on the environment?
Definition
Decomposition products are harmless
Term
What arrangement, reflux or distillation, should be used for the formation of ethanal and why?
Definition
Distillation
If reflux, further oxidation would occur and ethanoic acid would be formed
Term
How would you ensure a reading from a pH meter is accurate?
Definition
Collaborate with a solution of a known pH and plot a collaboration curve
Term
How could the melting point of asprin be measured?
Definition
Put sample in capillary tube and heat in melting point apparatus
Term
Why should a pH meter be collaborated before use?
Definition
pH meter may get less accurate over time
Term
What substance is most likely to oxidise Iron (II) ions when Iron (II) sulphate is used as a weed killer?
Definition
Oxygen
Term
Suggest a value for the pH of a 0.100 mol dm-3 solution of Iron (II) sulphate?
Definition
Anything in the range 4.0 - 6.9
Term
What is a chemical hazard when using H2SO4 and what is a safety precaution?
Definition
Acid is corrosive
Use gloves or eye protection
Term
Why is it an advantage to add thiocyanate ions to the iron (III) sulphate solution before measuring percentage absorbance?
Definition
To intensify the colour
Term
Why is it necessary to maintain a constant temperature in an experiment to measure the equilibrium constant?
Definition
Temperature affects the equilibrium constant
Term
What is one method for maintaining a constant temperature in an experiment?
Definition
Use a water bath
Term
What is observed when 1-chloropropane and ethanoyl chloride are separately added to an aqueous solution of silver nitrate?
Definition
1-chloropropane - no visible change
ethanoyl chloride - white precipitate
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