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Advanced Higher Chemistry > Techniques > Flashcards

Techniques Flashcards

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1
Q

What is stoichometry?

A

The ratio of things

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2
Q

What are the different types of analyses?

A

Quantitative analysis
Gravimetric analysis
Volumetric analysis

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3
Q

What does volumetric analysis involve?

A

Volumes

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4
Q

What does gravimetric analysis involve?

A

Masses

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5
Q

What happens in volumetric analysis?

A

Volumetric analysis uses a solution of exact concentration to determine the volume

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6
Q

What is a standard solution?

A

One of exact concentration

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7
Q

What is a standard solution prepared from?

A

A primary standard

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8
Q

What should a good primary standard be?

A

Should be stable when solid/ solution
Should be readily soluble
Should have a reasonably high formula mass

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9
Q

Why should a primary standard have a reasonably high G fm?

A

So that errors in weighing molar quantities are reduced

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10
Q

Why can’t sodium hydroxide be used as a primary standard?

A

Because it absorbs water and carbon dioxide

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11
Q

What are some common primary standards?

A

Oxalic acid
EDTA
potassium iodate

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12
Q

When are results said to be concordant?

A

When the results are within 0.1 of each other

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13
Q

What is meant by ‘weigh accurately approximately’?

A

The exact mass should be known/measured and should be close to the given value

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14
Q

What is gravimetric analysis?

A

Analytical determination of composition of a substances mass by chemically changing the substance

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15
Q

What is weighing by difference?

A

Weigh the empty weighing boat
weigh substance and weighing boat
Mass of substance=B-A

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16
Q

What is ‘heated to a constant mass’?

A 
Weigh hydrated substance in crucible
Heat crucible strongly
Cool in desiccator chamber
Weigh substance in crucible 
Repeat until mass is constant
17
Q

What is volumetric analysis?

A

Appreciation of the characteristics of substances that can be used as a primary standard

18
Q

What must a primary standard have?

A

High state of purity
Stability in air and in solution
Solubility
Reasonably high gram formula mass.

19
Q

How can results be improved?

A

If titre is less than 5ml, these are not acceptable

A larger volume of solution can be used or lower concentration of the known solution to improve accuracy

20
Q

What does a control do?

A

A control validates a technique and may consist of carrying out a determination on a solution of known concentration

21
Q

What is back titration?

A

Back titration is used to find the number of moles of a substance by reacting it with an excess volume of reactant of known concentration.

22
Q

When is back titration useful?

A

When trying to work out the quantity of a substance in an insoluble solid.

23
Q

What is distillation used for?

A

Distillation is used to purify a compound by separating it from a non-volatile or less volatile material

24
Q

What is refluxing?

A

A technique used to apply heat energy to a chemical reaction mixture over an extended period of time

25
Q

What is recrystallisation?

A

A technique used to purify solids based upon solubility

26
Q

What are the steps of recrystallisation?

A

Use small volume of appropriate solvent
Use hot solvent
Filter to remove impurities
Cool for crystals to form

27
Q

What can melting point give an indication of?

A

The purity of an organic compound

28
Q

What does a large temperature range suggest?

A

Lots of impurities

29
Q

What is 1ppm equal to?

A

1mg in 1kg

30
Q

What are the causes of error or low yields?

A 
Impurity present in reactants
Incomplete reaction/side reaction
Physical error when transferring reactants
Weighing errors
Low grade of glassware
31
Q

Why are the calculated and experimental values in temperature different?

A

Sample may be impure

32
Q

What can be said about the empirical formula and molecular formula?

A

They are the same!!

Advanced Higher Chemistry (12 decks)

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