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Chemsitry > Core Practicals > Flashcards

Core Practicals Flashcards

1
Q

How measure the molar volume of a gas

A

Collection of gas method (upturned measuring cylinder in water)
Gas syringe

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2
Q

Potential errors with gas syringe

A

Gas escaped before insertion
Strung sticks
Gas being insoluble in water

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3
Q

Method for measuring molar volume of gas

A

Measure acid and transfer to conical flask
Attach syringe/use gas collection method
Measure the mass of bottle with CaCO3
Add CaCO3
Quickly add bung before gas escapes
Read result
Reweigh empty bottle

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4
Q

Heating in a crucible method

A

Weigh empty dry crucible and lid
Add 2g of hydrated calcium sulphate
Reweigh
Heat strongly with a Bunsen
Allow to call
Reweigh
Continue until a constant mass is reached- shows end of reaction

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5
Q

Use of heating in a crucible

A

Water of crystallisation can be removed from calcium sulphate crystals

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6
Q

How to make a standard solution

A

Weigh the sample bottle with required mass of solid on balance
Transfer to beaker- use washings
Reweigh empty bottle and record mass difference
Add distilled water and dissolve usinh glass rod
Pour into volumetric flask
Add all washings
Make up to mark using distilled water
Invert flask several times

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7
Q

Phenophalein colour change

A

Pink/purple to colourless

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8
Q

Methyl orange colour change

A

Acid: red to orange
Alkali: yellow to orange

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9
Q

How to calculate uncertainty

A

Uncertainty =(uncertainty/measure made on apparatus) x 100

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10
Q

How to reduce uncertainty in titration

A

Make the titre a larger volume
Increase volume or concentration of solution being titrated
Means error is a Lower percentage

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11
Q

How to test rate of hydrolysis of halogenoalkanes

A

Arrange three test tubes in a row
Add three drops of Halogenoalkane- 1-chlorobutane , 1-bromobutane and 1-iodobutane
Add silver nitrate to each Halogenoalkane
Put all three simultaneously in water bath
Note order of precipitates forming

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12
Q

What is the ppt in test of hydrolysis of Halogenoalkane and why is it’s formation important

A

Halide combines with silver ion to form a silver halide ppt
Precipitate only formed when halide ion has left the haloalkane and thus rate of formation can be used to compare reactivity

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13
Q

What is the formation speed of silver halogen ppt showing

A

Quicker the ppt formed, faster the reaction and more reactive the haloalkane

Rate of reaction depends on strength of C-X bond. Weaker the bond, faster the reaction

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14
Q

Rate of silver halide ppt formation fastest to slowest and colour formed

A

AgCl-Yellow
AgBr-Cream
AgI-White

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15
Q

Differences between partial and full oxidisation of primary alcohol

A

Partial uses limited amount of potassium dichromate, full uses in excess
Partial distills of aldehyde as formed
Full heats under reflux

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16
Q

Reaction for partial oxidation of propan-1-ol

A

CH3CH2CHOH + [O] becomes CH3CH2CHO + H2O

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17
Q

Method for partial oxidation of propan-1-ol

A

Place dilute Sulfuric acid in a flask
Add 3G of potassium dichromate and add anti-bumping granules
Shake until solution complete

Add propan-1-ol in drops
Shake flask to mix contents

Gently heat and distil liquid into test tube

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18
Q

Distillation equipment

A

Round bottom flask being heated
Thermometer in top
Heated flask attached to Liebig condenser
Eventually runs to another flask

KEY: water in at bottom to go against gravity and ensure more efficient cooling

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19
Q

Observation on full oxidation of alcohol

A

Orange dichromate ion reduces to green Cr3+ ion

20
Q

Equation for full oxidation of propan-1-ol

A

CH3CH2CH2OH + [O] becomes CH3CH2COOH + H2O

21
Q

Method for full oxidation of alcohol

A

Place water and sodium dichromate in boiling tube, then shake
Place Propan-1-ol, water and anti-bumping granules into round bottom flask
Set up for reflux
Add conc H2SO4 down condenser in drops and add sodium dichromate in drops
When all sodium dichromate added, use low Bunsen flame for 10 mins
At the end of that time set up for distillation

22
Q

Equipment for reflux

A

Round bottom flask heated from bottom
Condenser
Water in at bottom

23
Q

What is the use of anti-bumping granules

A

Prevents vigorous boiling by making small bubbles form

24
Q

Detailed method for preparing and purifying an ester

A

Propan-1-ol and Ethanolic acid mixed in round bottomed flask
Conc H2SO4 added drop by drop
Keep contents of flask well-shaken and cooled in ice-water bath

When all acid added, a reflux condenser is fitted and mixture boiled for 30 mins
Mixture cooled and prepared for distillation

Distillate placed in seperating funnel and shaken
30% sodium carbonate solution makes up roughly half of volume
Aqueous layer discarded

Crude ester shaken in seperating funnel with half its volume of Calcium chloride solution
Lower layer discarded

Ester ran into clean dry flash with anhydrous calcium chloride

Ester filtered into clean dry flask with anti bumping granules and is distilled
Collect 100-103degrees C fraction

25
Q

Flame test method

A

Use a nichrome wire
Clean the wire by dipping in conc HCl and heat in Bunsen
Dip wire in powdered solid
Place at edge of flame and record colour

26
Q

Method for dilute NaOH test

A

Place drops of Metal ion solution in a test tube
Add drops of NaOH and mix well
Continue to add NaOH, by drops with shaking, until in excess

27
Q

Result of Magnesium hydroxide and sodium hydroxide

A

Insoluble min water
White ppt

28
Q

Result of calcium hydroxide and sodium hydroxide

A

Partially soluble in water
White pot

29
Q

Will strontium and barium produce a result in sodium hydroxide test

A

No

Due to high solubility

30
Q

How to test for ammonium ions

A

Place drops of ammonium chloride
Add drops of NaOH
Shake mixture well
Warm mixture in test tube using water bath
Test fumes released by using damp red litmus paper

31
Q

Results of ammonium test

A

Alkaline ammonium is released tuning red litmus paper blue

32
Q

Test for an Alkene and result

A

Add bromine water

Alkene will decolourise bromine water

33
Q

Reaction of 2-4 DNP (aka Brady’s reagent)

A

Tracts with both aldehydes and ketones

Yellow ppt

34
Q

Tollens reagent test

A

Test for an aldehyde
Heat gently
Aldehydes are oxidised by tollens leading to a silver mirror formed

35
Q

Fehlings solution test

A

Heat gently
Aldehydes only oxidised by Fehlings solution
Blue copper ions change to red ppt

36
Q

PCl5 test for alcohol and carboxylic acid

A

Add PCl5

Positive result- misty white fumes

37
Q

What functional groups does sodium metal test for and what is a positive result

A

Alcohols, phenols and carboxylic acids

Effervescence due to H2 gas

38
Q

What does sodium carbonate test for and what is a positive result

A

Carboxylic acid

Effervescence of CO2

39
Q

What does sodium dichromate and sulphuric acid test for

A

Primary/secondary alcohol and aldehyde

Orange to green

40
Q

Methods to measure enthalpy change experimentally

A

Calorimetric method- one substance mixed with another in insulated container. Temp rise measured

Flame calorimetry- used for enthalpy of combustion. Spirit burner used and the change in mass Is measured

41
Q

Errors with calorimetric method of enthalpy change

A

Energy loss to surroundings
Approximation in SHC of solution
Neglecting SHC of calorimeter
Reaction may be incomplete or slow

42
Q

What is the use of a salt bridge

A

Used to connect circuit- free moving ions conduct charge

Made from filter paper soaked in salt solution, normally Potassium nitrate

Should be in reactive with electrodes and electrolyte

43
Q

When and why is a platinum electrode used

A

If one or both of the half cells do not contain a conducting metal

Platinum used as unreactive and can conduct electricity

44
Q

Different ways to measure rate of reaction and when used

A

Change in vol of gas- used when moles of gas changes
Measurement of change of mass- used when gas formed which can escape
Titrating samples of reaction mixture- used for suitable products
Colorimity- used if change in colour
Change in conductivity- used if Change in number of ions

45
Q

What is continuous monitoring and how is it fine

A

Following one experiment by recording change in concentration

46
Q

How to calculate activation energy using Arrhenius equation

A

Draw graph of 1/T against ln(rate)

Gradient of line = -Ea/R

Ea = -gradient x R

47
Q

What does barium chloride test for

A

Sulfate and phosphorous ions

Chemsitry (15 decks)

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