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5.01 A-Level Physical KW > 1.2 Amount of Substance > Flashcards

1.2 Amount of Substance Flashcards

1
Q

How do you know a chemical reaction has taken place?

A 
Colour change
Effervescence 
Temperature 
Light
Precipitate formed (cloudy)
Change in mass 
Sound
pH change
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2
Q

What do the small numbers represent within an equation?

A

They say how many atoms of that element are within the molecule

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3
Q

What is the Mr?

A

Relative Molecular Mass

The average mass of a molecule compared to 1/12 of the mass of one atom of carbon-12

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4
Q

What is the Ar?

A

Relative Atomic Mass

Average mass of an atom compared to 1/12 of one atom of carbon-12

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5
Q

What is used to compared relative masses?

A

The carbon 12 scale

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6
Q

What unit is used for Mr?

A

gmol ^-1

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7
Q

How do you calculate the Mr?

A

Add up all the atomic mass numbers in the molecule

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8
Q

How to work out percentage of an element within a compound?

A

Ar of element
Divided by
Mr of compound
Multiplied by 100

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9
Q

How do you work out the transition element charges?

A 
They should be given to you as a roman numeral 
I - 1+
II - 2+
III - 3+ 
IV - 4+ 
Etc....
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10
Q

Definition of an element?

A

A substance in which all the atoms contain the same number of protons

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11
Q

Definition of an atom?

A

The smallest part of an element that can take part in a chemical reaction

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12
Q

Definition of an ion?

A

An atom that has either lost electrons to form a positive ion or gained electrons to form a negative ion
Atoms do this to make a full outer shell of electrons

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13
Q

Definition of a molecule?

A

The smallest particle of a compound (a combination of two or more elements)
Also a name for elements that cannot exist as atoms in a free state

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14
Q

Which elements cannot exist as atoms in a free state?

A 
Diatomic molecules
Hydrogen - H2
Nitrogen - N2
Chlorine - Cl2
Iodine - I2
Oxygen - O2
Fluorine - F2
Bromine - Br2
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15
Q

What is the charge of ammonium?

A

NH4 ^ 1+

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16
Q

What is the charge of chloride, bromide and iodide?

A

Cl ^ 1-
Br ^ 1-
I ^ 1-

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17
Q

What is the charge of hydroxide?

A

OH ^ 1-

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18
Q

What is the charge of nitrate and nitrite?

A

NO3 ^ 1-

NO2 ^ 1-

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19
Q

What is the charge of hydrogen carbonate and hydrogen sulphate?

A

HCO3 ^ 1-

HSO4 ^ 1-

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20
Q

What is the charges of sulphate, sulphite and sulphide?

A

SO4 ^ 2-
SO3 ^ 2-
S2 ^ 1-

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21
Q

What is the charges of oxide, carbonate and phosphate?

A

O2 ^ 1-
CO3 ^ 2-
PO4 ^ 3-

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22
Q

What does aqueous mean?

A

Dissolved in water

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23
Q 
What are the symbols for:
hydrochloric acid
Sulphuric acid
Nitric acid
Ethanoic acid
A

HCl
H2SO4
HNO3
CH3COOH

24
Q

What are the symbols for ammonia
Carbon monoxide
Sulphur dioxide
Methane

A

NH3
CO
SO2
CH4

26
Q

What is the law of conservation of mass?

A

Total mass of reactants = total mass of products

27
Q

What are the rules for balancing combustion reactions?

A

Balance the carbons with CO2
Balance the hydrogen with H2O
Balance the oxygen with O2

28
Q

What can you use with balancing equations?

A

Halves for the big numbers

29
Q

What can you not do when balancing equations?

A

Use or adjust small numbers to balance

30
Q

What must you remember about significant figures?

A

Your answer should always be the same number of significant figures as the smallest significant figure in the question

31
Q

How do you do empirical formula?

A

Divide the % or mass of the element by it’s Ar
Divide all the answers by the smallest answer produced

The whole numbers produced shows the EF
You may have to multiply the ratios to create whole numbers

32
Q

How do you work out the molecular formula?

A

Mr/EF mass = x

x multiplied by EF

33
Q

What does a mole contain?

A

1 mole of any substance contains 6.02 x10 ^23 particles

Or Avagadros number

34
Q

What is Avagadros number? What contains it?

A

6.02 x10 ^23

The Ar and Mr of a substance in grams contains Avagadros number of particles

35
Q

What equation works out moles?

A

Mass
———
Moles X RFM

36
Q

What units are used for mass, moles and RFM?

A

Mass - g
Moles - mol
RFM (Ar/Mr) - gmol ^-1

37
Q

What do the large numbers represent in balancing equations?

A

The number of moles

38
Q

How do you calculate reacting masses?

A

Check equation is balanced
Use the mass in the question divided by it’s RFM to work out the moles
Use the moles to multiply by the RFM of the substance you are working out

If it asks for the molecules multiply Be Avagadros
If it asks for atoms multiply by Avagadros then the number of the atoms

39
Q

What is atom economy?

A

RFM of Useful products
———————————— x100
RFM of ALL the reactants

40
Q

How can any atom economy be improved?

A

Find a use for the waste/non useful product

Sell the waste product

41
Q

What should you remember in atom economy?

A

Take note of the big numbers when working out the RFM’s

42
Q

What is significant about impure substances?

A

You cannot work out the moles or masses of impure substances

43
Q

What is the second equation that works out moles?

A

Moles
—————————
Concentration X Volume

44
Q

What is the unit of volume (in mol, conc, vol)? Converting?

A

Dm^3

Cm^3 / 1000 = dm^3

45
Q

What are the units for concentration?

A

mol dm^3

Or

M

46
Q

What is the equation for gases at room temperature and pressure?

A

Volumes
———————
Moles X 24dm^3

47
Q

What is the equation for gases at standard temperature and pressure?

A

Volumes
———————
Moles X 22.4 dm^3

48
Q

What are the conditions for room temperature and pressure?

A

298K

100kPa

49
Q

What are the conditions for standard temperature and pressure?

A

273K

101.3 kPa

50
Q

What is the ideal gas equation?

A

V P = n R T

V - volume
P - pressure 
n - moles
R - ideal gas constant 
T - temperature
51
Q

Units for pressure? Conversions?

A

Pascals - Pa

kPa X 1000 = Pa

52
Q

What is the ideal gas constant?

A

8.31 J k^-1 mol^-1

53
Q

Units for temperature? Conversions?

A

Kelvin (K)

Celsius + 273 = Kelvin

54
Q

Units for volume (in pv=nrt)? Conversions?

A

m^3

cm^3 / 1000000 = m^3
dm^3 / 1000 = m^3

55
Q

What is the equation for instrument error percentage?

A

Number of measurements X Instrument error
——————————————
Measurement value

All multiplied by 100

56
Q

How can you decrease instrument error?

A

Increase the measurement value

57
Q

What do you do if you’re bot told which reactant is in excess?

A

Find the limiting reagent by working out the moles of both

58
Q

How to work out the limiting reagents?

A

Work out the moles of both
Use the moles of one of the reactants to predict the moles of the other reactant
Compare the predicted moles to the actual moles
If the actual moles is greater than the predicted then that reactant is in excess
If the actual moles is smaller than the predicted moles then that reactant is the limiting factor

5.01 A-Level Physical KW (12 decks)

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