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Aqa A Level Chemistry > Amount Of Substance > Flashcards

Amount Of Substance Flashcards

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1
Q

What does one mole contain and what is this known as?

A

6.02x10^23 particles known as Avogadro’s number

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2
Q

Does it matter what the particular are?

A

No they can be atoms, molecules, electrons, ions, penguins, dinosaurs- anything

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3
Q

Number of particles=

A

Number of moles x Avogadro’s number

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4
Q

What is 1 mole of a substance mass equal to?

A

It’s relative molecular mass in grand

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5
Q

How can you work Mr?

A

Number of moles =

Mass of substance/ Mr

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6
Q

What’s the concentration of a solution?

A

How many moles are dissolved per 1dm3 of solution units are mol dm^(-3)

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7
Q

Concentration equation

A

Number of moles= concentration (mol dm^(-3)) x volume dm^(-3)

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8
Q

1dm3=

A

1000cm3

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9
Q

To convert from cm3 to dm3?

A

divide by 1000

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10
Q

Ideal gas equation?

A

pV=nRT

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11
Q

How to convert to K

A

oC+ 273

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12
Q

Units for ideal gas equation

A 
P= (pa)
V= (m3)
n= number of moles 
R=8.31
T= K
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13
Q

1cm3 is

A

1x10^(-6) m3

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14
Q

1dm3 is

A

1 x10^(-3) m3

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15
Q

Balanced equations have the same?

A

Number of atoms on both sides

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16
Q

How do you balance an equation rules?

A

Change number in front

DON’T CHANGE NUMBER IN FORMULA

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17
Q

How to balance equation?

A

Work out number of atoms each side
Change according
Can use 1/2 at front
Check it balances

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18
Q

What else can you write?

A

Ionic equation for any reaction involving ions happen in solution
In ionic equation only reacting particles and products formed included
Check charges balance

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19
Q

State symbols

A 
S= solid 
L= liquid 
G= gas
Aq= aqueous in water
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20
Q

Name two other things equation balancing can be used for?

A

Work out gas volumes

Work out masses

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21
Q

What do you before titration?

A

Make up standard solution

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22
Q

Explain standard solutions

A

Any solution you know exact concentration

Involved dissolving known amount of solid in known amount of water to create known concentration

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23
Q

How to make standard solution step 1?

A

Work out number of moles of x you need using

Moles=c/v

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24
Q

How to make standard solution step 2?

A

Work out how many grams of x needed using formula

Mass= moles x Mr

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25
Q

Volumes for standard solutions

A

Dm3

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26
Q

How to make standard solution step 3?

A

Place weighting boat on digital balance and weigh out this mass of solid. Tip into beaker and reweigh boat which may contain traces of solid. Subtract mass of boat and solid together to find precise mass of solid used

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27
Q

How to make standard solution step 4?

A

Add distilled water to beaker and stir until all x has dissolved

28
Q

How to make standard solution step 5?

A

Tip solution into volumetric flash make sure right size for volume you’re making. Use funnel to make sure it all goes in

29
Q

How to make standard solution step 6?

A

Rinse beaker and stirring rod with distilled water and add that to flask making sure no solute clinging to beaker to rid

30
Q

How to make standard solution step 7?

A

Top flask up to correct volume with more distilled water. Make sure bottom of meniscus reaches line. When you get close to line add water drop by drop. If you go over you’ll have to start again.

31
Q

How to make standard solution step 8?

A

Stopper flask and turn upside down few times to make sure mixed

32
Q

What does a titration allow?

A

You to find out exactly how much acid is needed to neutralise measured quantity of alkali

33
Q

What can you use titration information to do?

A

Work out concentration of alkali

34
Q

Step 1 of titration

A

Using pipette measure out set volume of solution that you know the concentration of. Put in a flask

35
Q

Step 2 of titration

A

Add few drops of appropriate indicator to flask

36
Q

Step 3 of titration?

A

Fill burette with standard solution of ache remember exact concentration

37
Q

Step 4 of titration?

A

Use funnel to carefully pour acid into burette. Always do this below eye level to avoid any avid splashing to face or eyes (wear safety specs)

38
Q

Describe how to use pipette?

A

Pipettes measure only one volume of solution

Fill pipette to just above line and take pipette out of solution then drop level down carefully to line

39
Q

Step 5 of titration

A

Do rough titration to get idea where end point is. Add acid to alkali using burette giving flask regular swirl

40
Q

Step 6 of titration

A

Do accurate titration. Take initial reading to see exactly how much acid is in burette. Run acid in to within 2cm3 of end point. When at this stage add drop wise otherwise you don’t notice exactly when colour change happens and resulted won’t be accurate

41
Q

Step 7 of titration

A

Work out amount of acid used to neutralise a alkali.

Final reading- initial reading= titre

42
Q

Step 8 of titration

A

Repeat titration few times until three results are concordant (very similar)

43
Q

Step 9 of titration

A

Use results from each repeat to calculate

leave anomalous results when calculating mean as can distort answer

44
Q

Burettes

A

Measure different volumes and let you add solution drop by drop

45
Q

Indicators for titrations?

A

Methyl orange- yellow in acid, red in alkali

Phenolphthalein- pink in alkali, colourless in acid

46
Q

Indicator extra info?

A

Indicators change over very small pH range used so know exactly when reaction has ended
Use white tile to easily see end point
Don’t use universal indicator

47
Q

Step 10 of titrations

A

Use mean volume to find concentration of solution in flask
Balanced equation
Work out moles of acid
Work out how many moles of alkali therefore
Work out concentration of alkali

48
Q

Titration method for volumes?

A

Balanced equation
Work out moles of acid
Work out moles of alkali
Work out volume

49
Q

Empirical formula

A

Simplest whole number ratio of atom of each element in a compound

50
Q

Molecular formula

A

Gives actual numbers of atoms of each element in a compound

51
Q

Molecular formula

A

Made up of whole number of empirical units

52
Q

Empirical formula how to find

A

N= mass/Mr
Divide by smallest of numbers
Use ratio and put in numbers as appropriate

53
Q

Can find empirical formula from?

A

Experiments

54
Q

Theorical mass of products?

A

Should be found in chemical reaction

Assumes no chemicals are lost in process. Can use mass of reactants and balanced equation to find it

55
Q

Actual mass of products?

A

Actual Yield always less than theorical Yield. Many reasons not all starting chemicals react fully, some chemicals are lost

56
Q

Percentage yield=

A

Actual yield/ theorical yield x100

57
Q

Percentage yield tells you

A

Tells you how wasteful process is based on product lost during process

58
Q

What doesn’t percentage yield tell you?

A

How wasteful reaction itself is. A reaction with 100% could still be wasteful if lot of atoms from reactants wind up in by-products rather than desired products

59
Q

Atom economy

A

Measure of the proportion of reactant atoms that become part of desired product rather than by-products in balanced chemical equation

60
Q

Atom economy=

A

Molecular mass of desired products/ sum of molecular masses of all reactants x100

61
Q

What should companies should try to use processes with?

A

High atom economies

62
Q

Processes with high atom economies are?

A

Better for the environment because they produce less waste
Make more efficient use of raw materials so more substainable
Less expensive

63
Q

Why is less waste good?

A

Any waste made needs to be disposed of safely so less made the better

64
Q

Why are they more sustainable?

A

Use up natural resources slower

65
Q

Why are they less expensive?

A

Company using processes with high atom economy will spend less on separating desired product from waste products and less on treating waste

66
Q

How is amount of substance measured?

A

Using unit called the mole

Aqa A Level Chemistry (12 decks)

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