Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chem Exam Q > Practicals Paper 2 > Flashcards

Practicals Paper 2 Flashcards

1
Q

What safety precaution should you use for irritant and corrosive

A

Wear goggles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Safety precaution for flammable

A

Keep away from naked flames

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

3 safety precautions for toxic substances

A

Wear gloves
Avoid skin contact
Wash hand after use

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

When removing water of crystallisation why should you not use large amount said calcium sulfate like 50g

Why can’t you use a wet crucible

Why can’t you use small amounts like 0.1g

A

Incomplete decomposition

Wet gives inaccurate result - mass loss would be too large as that water would also be lost

Percentage uncertainty would be too high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What to note down when measuring gas syringe reading

A

Temperature and pressure of room as that is what the volume of gas depends on

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are 3 potential errors when saying a gas syringe

A

Gas escapes before bung inserted
Syringe sticks
Some gases are water soluble so the true amounts isn’t measured

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the method of making a standard solution

A

Use weigh re weigh method to measure sample

Add to beaker

Add 100 cm distilled water and stir glass rod

Pour into 250 volumetric flask

Put washing from beaker into it

Make up to mark below meniscus with distilled water

Invert to ensure a uniform solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What’s better to than a measuring cylinder

A

Volumetric pipette

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

General method for carrying out a titration

A

Rinse the equipment with what it will be filled with (burette is acid pipette is alkali and conical flask with distilled water )

Pipette 25cm alkali into conical flask - touch surface of alkali with pipette to ensure correct amount of

Add acid solution from burrete

Make sure jet space is filled with acid

Add few drops of indicator and refer to end point colour change

Use white tile to help observe colour change

Swirling mixture while adding acid and add dropwise toward endpoint

Note b burrete reading before and after adding acid

Repeate until 2 concordant results

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why is a conical flask preferred in titrations

A

Easier to swirl the mixture without spilling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why is distilled water used to wash out the conical flask in titrations

A

It doesn’t affect the moles of the reagents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How to calculate percentage uncertainty

A

Uncertainty / measurement
X100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How to decrease percentage uncertainty in titrations

A

Increase volume and concentration of substance in conical flask

Reduce concentration of substance in burette

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How to reduce uncertainty when measuring mass

A

Use a mass balance requiring more decimal places

Use a larger mass

Weigh re weigh method

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the method for measuring the enthalpy change of anhydrous copper sulfate

A

Weigh out 3.9 to 4.1 g anhydrous copper sulfate (weigh re weigh )
Using a volumetric pipette place 25cm water into a polystyrene cup
Record temp at beginning
Record temp again for 0,1,2,3
At fourth minute add powder don’t record temp
Stir continuously
Re weight bottle
Take temp at minute 5 for 15 minutes
Plot graph of temp (y) against time (x)
Draw 2 line of best fit
Extrapolate to 4th minute
Use q = equation to calculate delta h
Repeats method with hydrated copper sulfate
Calculate final enthalpy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are 2errors of measuring enthalpy change of solution practical

A

Heat loss to surroundings
Specific heat capacity and density taken to be same as water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the Hess law diagram for RP2

A

Photo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

3 errors when measuring combustion enthalpy was using a flame calorimeter

A

Incomplete combustion of fuel
Evaporation of fuel
Heat loss

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the method for measuring rate of reaction using sodiumthiosulfate and HCl

A

Measure 10cm HCl and 10cm sodium thosulafte in clean cylinders
Put them into separate boiling tubes
Place them in water bath
Place flask at centre of large cross
Add sodium thiosulfate
Add HCl
Start watch
Until time cross disappears
Repeat at different temperatures

20
Q

Why is 1/t used in the experiment for disappearing cross

A

Amount of sulfur produced is the same and constant for each experiment
So the concentration is the same

21
Q

What precaution when handling acidified potassium dichromate

A

Wear gloves

22
Q

Method for oxidising propan1ol (partially)

A

Place dilute sulfur acid 10cm in a flask
Add potassium dichromate
Add anti bumping granules
Add porpanol in drops frk a burette - shake to mix
Gently heat and distill the product

23
Q

Where does the water go in in distillation and why

A

At the bottom
Goes against gravity which allows more efficient cooking and prevents back flow of water

24
Q

How to improve yield of distillate (2)

A

Collection flask can be cooled in ice

Only collect distillate at approximate boiling point of the aldehyde not higher

25
Q

Draw distillation apparatus

A

Phot

26
Q

Draw reflux apparatus

A

Photo

27
Q

What to remeber when drawing reflux apparatus and why

A

Don’t seal the wnd
Otherwise build up of gas pressure can cause apparatus to explode

28
Q

Acyl chloride test

A

Add silver nitrate
Steamy HCl fumes and white ppt Agcl
Vigour is reaction

29
Q

What is the method for the iodine clock experiment

A

Put all chemicals in separate burette
Measure out required volumes of each
Measure hydrogen peroxide into a test tube
Pour it into conical flask and start timer - stir
Time until first hint of blue / black appears
Repeate with different connections of potassium iodide

Keep temp same

30
Q

Gas syringe apparatus drawing

A

Photo

31
Q

Why is ethanoic anhydride used instead of of acyl chlorides (3)

A

Less corrosive
Less vulnerable to hydrolysis
Less dangerous

32
Q

How to make aspirin

A

Add 50 hydroxybenzouc acid and 4pm ethanoic anhydride to a pear shaped flask

Add phosphoric acid and stir

Fit with reflux condenser heat for 5 minutes in a water bath and add 2cm water

Pour into 40cm cold water in a beaker
Stir and run side of the beaker
Stand in ice bath
Collect product by reduced pressure filtration and wash with little water

33
Q

When making aspirin what are the steps for recrystallising

A

Dissolve in minimum amount of hot water

Hit filter solution through filter paper

Cool filter solution by inserting into beaker with ice

Use reduced pressure filtration to separate out crystals

Wash crystals with distilled water

Dry the crystals filter paper

34
Q

Why are the crystals filtered
Why are they dissolved in water
Why are they dried with agent

A

Remove insoluble impurities
Remove soluble impurities
Remove excess water

35
Q

Reduced pressure filtration drawn

A

Photo

36
Q

Why is the solution of aspirin cooled slowly

A

So that yield of crystals is increased

37
Q

How to measure melting point

A

Place sample in capillary tube
Put into melting point apparatus
Heat gradually

38
Q

Method for purifying an organic liquid

A

Put into a separating funnel
Wash product by adding sodium hydrogen carbonate to neutralise any remaining reactant acids
Allow layers to separate (lower density is upper layer )
Discard aqueous layer
Run organic layer inti conical flask and add anhydrous calcium chloride
Pour liquid into distillation flask
Distill to collect pure product

39
Q

Think layer chromatography method

A

Wear gloves and draw pencil line to 1cm tlc plate
Mark spots each sample equally spaced along line
Use capillary tube to add tiny drop
Allow plate to dry
Add solvent to beaker with lid must be below pencil line
Place tlc plate in chamber with lid
When it’s about 1cm from top remove plate and mark with pencil
Allow to dry in fume cupboard
Place plate under uv lamp
Draw around them lightly
Calculate the rf values

40
Q

Why wear gloves in tlc

A

Prevent contamination from hands to plate

41
Q

Why use pencil line

A

Won’t dissolve in solvent

42
Q

Why small drops

A

Don’t merge as they travel up and clear spots

43
Q

Why solvent beliw pencil line

A

If it’s too deep it will dissolve the spots form the plate

44
Q

Why a lid in chamber

A

Prevent evaporation of toxic solvent

45
Q

Why dry in fune cupboard

A

Solvent is toxic

46
Q

Movement by polar and non polar in solvents

A

Non polar compounds move faster in polar stationary phases

Chem Exam Q (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions