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Chemistry A Level > Practicals > Flashcards

Practicals Flashcards

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1
Q

RP1: Volumetric solution
Why is weighing boat reweighed?

A

To ensure accurate mass of solute added

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2
Q

RP1: Volumetric solution + titration
What is done to ensure there is a uniform concerntration of solution?

A

Invert the volumetric flask a few times

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3
Q

RP1: Volumetric solution + titration
Why are rinsings added?

A

To ensure all moles of solution has been transfered

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4
Q

RP1: Volumetric solution + titration
Colours of each indicator in alkali and acidic conditions

A

Methyl orange:
Acid- Red
Base- Yellow
Phenolphthalein:
Acid- Colourless
Base- Pink

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5
Q

RP1: Volumetric solution + titration
Why is a conical flask used for titration?

A

Easy to swirl

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6
Q

RP1: Volumetric solution + titration
Why can’t the inside of the burette be rinsed with water

A

This will affect the concerntration of alkali and affect the titre values

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7
Q

RP1: Volumetric solution + titration
Why is it okay to rinse the volumetric flask with water?

A

The overall moles of acid will be the same

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8
Q

RP2: Measurement of enthalpy change
Change to the experiment which will minimise heat loss

A

Use a good insulator as a cup

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9
Q

RP2: Measurement of enthalpy change
What would decrease the percentage uncertainty

A

Increasing number of moles of reactants added

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10
Q

RP3: Investigation into how the rate of reaction changes with temperature
Why are small amounts of the reactants used

A

To limit the amount of sulfur dioxide formed

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11
Q

RP3: Investigation into how the rate of reaction changes with temperature
Why isnt the experiement done between 1-10 degrees

A

Reaction would take too long

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12
Q

RP4:Testing for anions and cations
Flame test colours
Lithium
Sodium
Potassium
Calcium
Barium
Copper

A

Lithium: Red
Sodium: Yellow
Potassium: Lilac
Calcium: Orange/red
Barium: Green
Copper: Blue/green

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13
Q

RP5: Oxidation of alcohols under reflux and to form aldehydes

Methods of making sure aldehyde separated is pure.

A

Heat below boiling point of carboxylic acid and alcohol ensuring they don’t evaporate.

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14
Q

RP5: Oxidation of alcohols under reflux and to form aldehydes

Why might a ketone sample collected be impure?

A

The alcohol may have not oxidised completely

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15
Q

RP7: Measuring rate of reaction
Why is sodium hydrogencarbonate added before titration

A

To neutralise any remaining acid catalyst
Ensuring the reaction has stopped

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16
Q

RP7: Measuring rate of reaction
How to stop a reaction which does not use an acid catalyst

A

Cool/ quench it

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17
Q

RP8: Measuring EMF of electrochemical cell
What 2 solutions can be used in the salt bridge?

A

Aqueous silver nitrate or potassium chloride

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17
Q

RP8: Measuring EMF of electrochemical cell
What 2 solutions can be used in the salt bridge?

A

Aqueous silver nitrate or potassium chloride

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18
Q

RP8: Measuring EMF of electrochemical cell
How to tell if positive vs negative electrode

A

Positive: Removes electrons e.g electrons being taken in
Negative: Electrons being released e.g species being oxidised

Moves from negative to positive

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19
Q

RP8: Measuring EMF of electrochemical cell
Suggest why cells cannot be recharged

A

Reaction isnt reversible

20
Q

RP8: Measuring EMF of electrochemical cell
Why does EMF of cells drop after time

A

Eventually will discharge and reagents used up

21
Q

RP8: Measuring EMF of electrochemical cell
How to maintain constant EMF in fuel cells

A

Maintain constant concerntration of reactants

22
Q

RP8: Measuring EMF of electrochemical cell
Explain how salt bridge provides electrical connection

A

Contains mobile ions

23
Q

RP8: Measuring EMF of electrochemical cell
Suggest why recyharging of lithium cell may produce CO2

A

Energy to recharge from power stations

24
Q

RP9: Titration curves
How to select an indicator for a titration

A

Repeat with multiple indicators
Pick an indicator which changes colour rapidly at the equivalence point

25
Q

RP9: Titration curves
Why do you have to take funnel out of burette before titration?

A

Could produce droplets which would affect titre values

26
Q

RP9: Titration curves
Suggest a source of error when using a burette to carry out titrations

A

Air bubble may form- affecting titre values

27
Q

RP9: Titration curves
Suggest how washing the sides of conical flask improves accuracy of titre

A

Ensures all reagents able to mix
Makes sure any reagents on the side are included in reaction mixture

28
Q

RP9: Titration curves
Explain why adding water to conical flask doesn’t affect titre values

A

Moles of acid remains the same

29
Q

RP9: Titration curves
Method for calibrating PH probe

A

Measure probe in buffered solution of varying PH
Rinse PH prove with deionised water inbetween
Plot a graph of PH of buffer against PH reading on probe

30
Q

RP9: Titration curves
Suggest a way of improving accuracy approaching equivalence point

A

Add acid/ base dropwie and swirl

31
Q

RP10a: Production of asprin and Purification of soluble crystals
Process of purification of asprin

A

Add minimum amount of hot solvent
Filter to remove any insoluble impurities
Cool solution and stir to recrystalise
Filter solution under reduced pressure (Buchner funnel)
Rinse product off with cold solvent
Allow product to dry- between absorbent paper

32
Q

RP10a: Production of asprin and Purification of soluble crystals
Why is solution dissolved in minimum volume of hot solvent

A

So that solution is saturated and solution will form on cooling

33
Q

RP10a: Production of asprin and Purification of soluble crystals
Why is suction filtering used

A

This speeds up filtration

34
Q

RP10a: Production of asprin and Purification of soluble crystals
Why are crystals washed with cold solvent

A

To remove any soluble impurities

35
Q

RP10a: Production of asprin and Purification of soluble crystals
How to determine melting point

A

Add sample to a capillary tube attached to a thermometer in some heating oil
Heat slowly near melting point

36
Q

RP10a: Production of asprin and Purification of soluble crystals
How do impurities affect melting point

A

Lower melting points
Melts over a range of values

37
Q

RP10a: Production of asprin and Purification of soluble crystals
Industrial advantages of using ethanoic anhydride over ethanoyl chloride

A

Cheaper
Reacts less vigourously
Doesnt produce HCl gas

38
Q

RP10a: Production of asprin and Purification of soluble crystals
Safety precaution when using hot ethanol solvent

A

Heat below BP of ethanol
Dont heat under a naked flame

39
Q

RP10a: Production of asprin and Purification of soluble crystals
Purpose of adding cold solvent

A

To remove soluble impurities

40
Q

RP10B: Preparation of a pure organic liquid
Purifying an organic liquid method

A

Put mixture into separating funnel
Add sodium hydrogen carbonate
Allow layers to separate in the funnel
Run organic layer into conical flask and add drying agent
Distill product to make it entirely pure

41
Q

RP10B: Preparation of a pure organic liquid
Why is sodium hydrogencarbonate added

A

To help the organic and aqueous layers separate

42
Q

RP10B: Preparation of a pure organic liquid
Why is anhydrous sodium sulfate added

A

It is a drying agent

43
Q

RP10B: Preparation of a pure organic liquid
Why is tap of separating funnel opened periodically

A

To reduce pressure buildup as CO2 gas is produced

44
Q

RP10B: Preparation of a pure organic liquid
Why is anhydrous calcium chloride a good drying agents

A

It doesnt react with any compounds in the mixture

45
Q

RP10B: Preparation of a pure organic liquid
How do anti-bumping granules prevent bumping

A

Prevent formation of large bubbles

46
Q

RP10B: Preparation of a pure organic liquid
Why is an electric heater used in hydrolysis of esters

A

Ethanol is a product which is flammable

47
Q

RP10a: Production of asprin and Purification of soluble crystals
Loss of yeild means in aspirin process

A

Crystals lost when filtering/ washing
Some products remain in solution
Other side reactions occuring

Chemistry A Level (30 decks)

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