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Chemistry > Practical Skills > Flashcards

Practical Skills Flashcards

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1
Q

How do u make a volumetric solution

A
  • Weigh out using a weighing boat the mass of solid needed
  • Dissolve solid in a beaker using distilled water. Include washings
  • Use funnel to transfer solution to a volumetric flask
  • make up to mark using distilled water
  • then invert to mix
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2
Q

How do you carry out a titration

A
  • Rinse burette and pipettes with correct solutions
  • fill burette using a plastic funnel make sure there are no bubbles
  • when using pipette allow to drain and touch tip to surface. Put into conical flask
  • add 2 drops of indicators
  • swirl solution and add from burette
  • read burette to 0.5 cm3
  • repeat process to get concordant results
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3
Q

What are some of the sources of error in an enthalpy change experiment

A

Heat loss

Not taking into account the specific heat capacity of cup

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4
Q

5 things to consider when assessing uncertainty

A
  • Resolution of instrument - manufactures tolerance on instrument
  • judgements made
  • procedure adopted
  • size of increments
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5
Q

How to calculate percentage uncertainty

A

Uncertainty
————- X100
Value

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6
Q

How to calculate overall apparatus uncertainty

A

Add all the percentage errors together

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7
Q

What are 3 uncertainties in titre

A

Reading the burette at start of titration
Reading the burette at end of titration
Judging the end point to within one drop

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8
Q

7 improvements that can be made to an investigation

A
  • Repeating to get more results increases reliability
  • change concentration of solution to reduce error
  • change the size of pipette to reduce error
  • weighing a larger mass to reduce error
  • use more accurate apparatus
  • improve lagging in calorimetry experiment
  • control temperature
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9
Q

Why repeat experiments

A

Repeating improves reliability and identifies anomalies

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10
Q

Why test more than one sample

A

Samples can have a different composition and consistency

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11
Q

What should you do if a substance is corrosive

A

Handle with care wash spillages off skin or wear gloves and eye protection should be worn

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12
Q

What should you do if a substance is an irritant

A

Gloves and eye protection

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13
Q

What should you do if a substance is flammable

A

Keep well away from flame

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14
Q

What should you do if a substance is toxic

A

Wash hands after use.

Toxicity depends on dosage if possible use fum cupboard

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15
Q

Define accuracy

A

A measurement result is considered accurate if judged to be close to true value

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16
Q

Define calibration

A

Marking a scale on a measuring instrument

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17
Q

Define data

A

Information that has been collected

18
Q

Define measurement error

A

The difference between a measured value and the true value.

19
Q

Define anomalies

A

Values in a set of results which are judged not to be part of the variation cause by random uncertainty

20
Q

Define random error

A

These cause readings to be spread about the true value due to results varying. Cannot be corrected

21
Q

Define systematic error

A

Cause reading to differ from the true value by a consistent amount each time

22
Q

Define zero error

A

Any indication the measuring systems is giving a false reading

23
Q

Define categoric variables

A

Values that are labelled

24
Q

How to test for carbonate ions

A

Add HCl
Get effervescence

CO3 2- + 2 H+ = CO2 + H2O

25
Q

Test for sulphate ions

A

Add HCl then barium chloride

White precipitate

SO42- + Ba2+= BaSO4

26
Q

Test for hydroxide ions

A

Add NH4 +
Ammonia gas produced

OH- + NH4 + = NH3 +H2O

27
Q

Halide ion tests

A 
Add dilute nitric acid then silver nitrate 
Cl- white 
Br- cream 
I - yellow 
Then add NH3 
Cl - dissolve 
Br - dissolve in concentrated 
I- turns white in concentrated
28
Q

Equations for Halide ions tests

A

Cl-(aq) + Ag +(aq) —-AgCl(s)

29
Q

Carbon dioxide test

A
  1. Gives very weak acid

2. Bubbling through limewater gives a white precipitate

30
Q

Sulphur dioxide gas test

A
  1. Chocking smell give weakly acidic solution

2. When gas passed through paper soaked in potassium dichromate so reduced to green blue chromium (III) ions

31
Q

Test for hydrogen sulphide ions

A

Smell of bad eggs

Passed over paper soaked in less nitrate solution to give a silvery precipitate

32
Q

Hydrogen halide gas tests

A

colourless gas produce misty fumes in moist surface

Gas passed over gaseous ammonia and white fumes observed

33
Q

Test for ammonia gas

A

Pungent smell

Comes into contact with gaseous hydrogen chloride white fumes are observed

34
Q

Test for chlorine gas

A

A pale green gas

Turns moist litmus paper first red and then white

35
Q

Test for Mg 2+ ions

A

Add dilute sodium hydroxide
Will give white precipitate because is much more insoluble
Mg2+ + 2OH- – Mg(OH)2

36
Q

Testing for Ba2+ ions

A

add dilute sodium sulphate Na2SO4

Give white precipitate because more insoluble

Ba2+ + SO4 2- — BaSO4

37
Q

Test for alkene

A

Add bromine water and it will decolourise

38
Q

Test for OH alcohols

A

Warm with acidified potassium dichromate
K2Cr2O7

Turns from orange to green

39
Q

Test for aldehyde

CHO

A
  1. Warm with tollens reagent = a sliver mirror
  2. Add fehlings solution = blue to brick red precipitate
  3. Acidified K2Cr2O7 turns orange to greens
40
Q

Test for halogenalkane

A

Add HNO3
Add AgNO3

Cl = white 
Br = cream 
I = yellow
41
Q

Test for carboxylic acid

A

Add Na2CO3 give effervescence

Then litmus paper turn red

Chemistry (29 decks)

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