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Chemistry A Level > Moles > Flashcards

Moles Flashcards

1
Q

Equation relating moles, volume (dm^3) and 24

A

Moles = volume (dm^3)/24

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2
Q

Equation relating moles, pressure (Pa), volume (m^3), gas constant (8.314JK^-1mol^-1) and temperature (K)

A

n = PV/RT

PV = nRT

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3
Q

What are the two units for pressure?

A

Nm^-2

Pa

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4
Q

How to covert volume in cm^3 to m^3

A

x 10^-6

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5
Q

How to convert volume in dm^3 to cm^3

A

x1000

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6
Q

How to work out temperature in K

A

°C + 273

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7
Q

Atom

A

The smallest unit of an element that can exist

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8
Q

Molecule

A

The smallest part of an element or compound which can exist alone under normal conditions

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9
Q

Ion

A

An atom or group of atoms possessing a charge

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10
Q

Element

A

A substance containing only one type of atom

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11
Q

Compound

A

A substance containing two or more different elements that have been chemically combined

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12
Q

Empirical formulae

A

Simplest ratio showing the different types of atom present in a substance

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13
Q

Molecular formulae

A

Actual numbers of each type of atom in a molecule of the substance

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14
Q

Avogadro’s constant (L)

A
  • the number of particles in 1 mole of substance

* 6.02 x 10^23

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15
Q

Molar mass

A
  • mass per mole of substance

* gmol-1

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16
Q

To find molecular formula…

A

… you must divide molecular mass by empirical mass

17
Q

To find molecular formulae from masses…

A

… divide masses of elements by RAM, find the ratio of the elements and then calculate as above

18
Q

Mole

A

Unit for amount of substance

19
Q

Volume α

A

Moles x temperature

Moles/pressure

This is the universal gas constant (R)

20
Q

Titrations - basics

A

Method of finding out how much of one substances will react with how much of another

21
Q

Titration - process of rough reading

A

1) add a pipette-filler to a glass pipette
2) draw some of the solution into the pipette. Tilt the pipette and rotate it
3) discard the rinsing solution
4) draw the solution into the pipette until the bottom of the meniscus is on the mark
5) release the solution into a clean conical flask
6) when no more solution emerges from the burette, touch the lip of the burette against the side of the conical flask. Some of the liquid will remain in the tip
7) a suitable indicator added to the flask
8) place the flask on a white tile under the burette
9) hold the flask in the dominant hand and swirl
10) add the solution from the burette until the indicator changes colour. Note the reading on the burette- rough reading

22
Q

Why tilt and rotate the pipette?

A

All of the surfaces are rinsed in solution

23
Q

It does not matter if the conical flask…

A

… is wet

24
Q

Why is it okay for liquid to remain in the tip of the pipette?

A

It is calibrated to take this into account

25
Q

How should the burette tap be controlled?

A
  • by the non-dominant hand
  • first and second fingers behind the tap
  • thumb in front of it
26
Q

Titration - process after rough reading

A

1) discard the contents of the flask and rinse it with two water and then distilled water
2) repeat the process, adding the solution from the burette fairly slowly with continual stirring. As the level of the burette approaches that of the rough reading, add the solution drop by drop. When one drop changes the colour of the indicator, allow the solution to drain down the sides of the burette before taking the reading
3) reading should continue to be taken in this way until one rough and two accurate readings are within 0.20cm^3 of each other; concordant readings are obtained
4) calculations should be based on the mean average of the two accurate concordant readings

27
Q

Accurate burette readings should be taken to…

A

… two decimal places, the second decimal being either 0 or 5

28
Q

Error is caused by the fact that…

A

… all apparatus used to take measurements have uncertainties associated with them

29
Q

Error is dependent on…

A

… the measuring device, and the amount being measured

30
Q

In general, most apparatus few be read to…

A

… half a scale division

31
Q

Percentage error

A

[(Apparatus uncertainty) / (amount being measured)] x100

32
Q

The larger the quantity being measured

A
  • the less the percentage error
  • increase volume by dilution
  • increase mass
33
Q

Measuring pipette uncertainties

A

+- 0.1^cm3

34
Q

Measuring burette uncertainties

A

+-0.05cm^3

35
Q

If two readings are taken…

A

… the uncertainty occurs twice, so the value doubled

36
Q

Doubling concentrations…

A
  • doubles percentage error

* burette reading would be half the original

37
Q

Percentage atom economy

A

[ (molar mass of useful product) / (total molar mass of starting materials) ] x 100

Chemistry A Level (12 decks)

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