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A-level Chemistry Edexcel Unit 6 Comprehensive Study Guide 100% Pass
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A-level Chemistry Edexcel Unit 6Comprehensive Study Guide 100% Pass
test for water - Answer>>CoCl2 = blue to pink
CuSO4 = white to blue
Give the reason why water is added when preparing benzoic acid
- Answer>>To remove excess acyl chloride
test for CO2 - Answer>>bubble gas through lime water
(CaCOH)2
turns cloudy
Explain in terms of change of state how the process of heating
under reflux works - Answer>>as liquid boils vapour is cooled
and condenses back to liquid
absorbs water - Answer>>CaCl2
Give reasons why it is often necessary to heat chemicals under
reflux - Answer>>1. It prevents escape of reactants and
products
2. Enables flammable liquids to be heated safely
3. Allows for a complete reaction
Iodoform Test method - Answer>>- add I2 to alkaline solution til
brown turns colourless
- I2 and sodium hydroxide solution
- add KI
- positive = with carbonyl with methyl group = yellow ppt
how species such as CH₃CHOH⁺ is formed from a molecule of
compound X - Answer>>Species is formed by loss of CH₃ group
,Salt bridge - Answer>>filter paper and KNO3
suggest the best way to obtain some pure 1-methyl-2,4-
dinitrobenzene after the distillation. - Answer>>Fractional
distillation followed by recrystallisation
explain why when preparing nitrobenzene steps are taken so that
the reaction mixture is always at or below room temperature -
Answer>>To ensure only mono-substitution
what neutralises excess acid? - Answer>>= sodium hydrogen
carbonate
= effervescence (CO2)
Potassium manganate (VII) - Answer>>- indicator not required
for titration
- self indicating
= colourless to pink
explain why generally working from high to low concentration
would be less accurate - Answer>>increases the possibility of
contamination of ions due to residues from earlier experiments.
Flame Test Method - Answer>>1.) use nichrome wire
2.) dip wire in conc HCl to clean
3.) dip wire in solid
4.) place in hot bunsen flame and observe flame colour
outline how you would use the apparatus to prepare 100cm³ of
0.1moldm⁻³ solution of X starting from 1moldm⁻³ of X. -
Answer>>1. Use a pipette to measure 10cm³ of the 1moldm ⁻³
of X.
2. Transfer this to a 100cm³ volumetric flask.
, 3. Make the solution up to the mark with distilled water and then
mix.
Test for Ammonia - Answer>>= damp red litmus paper turns
blue
= react with HCl gas > gives dense white smoke
Name the reagents that are required for the iodoform test -
Answer>>Sodium hydroxide and iodine solution .
Recrystallization Method - Answer>>1.) dissolve crystals in min.
volume of hot ethyl ethanoate (solvent /water)
2.) filter to remove soluble impurities and allow to cool
3.) filter and wash with small amount of cold solvent (water bath
and vacuum filtration)
4.) dry between filter paper or with warm oven
Describe the procedure for carrying out the iodoform test. -
Answer>>mix the reactants together and heat.
Why is solid white? (trans metal) - Answer>>= d orbitals can't
split therefore no colour as no ligand is present
How would you show that the decomposition was complete -
Answer>>Heat to a constant mass.
Observation when a gas is evolved from a liquid -
Answer>>Bubbles.
Calibrate pH meter - Answer>>= use alkaline buffer solution
and acidic buffer solution
= then measure pH
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