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Separate Chemistry > T5: Amount of Substance > Flashcards

T5: Amount of Substance Flashcards

1
Q

Hydrogen + Oxygen -> Water balanced equation

A

2H2(g) + O2(g) -> 2H2O(l)

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2
Q

chemical formulae rules

A
  • elements written as 1 atom: all metals, noble gases, carbon, silicon (Na, Mg, Ca)
  • diatomic elements: N2, O2, F2, Cl2, Br2, I2
  • covalent compounds: formulae indicated by name (carbon dioxide -> CO2)
  • ionic compounds: determine from charges on individual ions
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3
Q

state symbol rules

A
  • solids (s) -> giant ionic substances, metals, large simple molecular substances (I2), macromolecular structures (C, Si, SiO2)
  • liquids (l) -> relatively large simple molecular substances (H2O, Br2), Mercury (Hg)
  • gases (g) -> relatively small simple molecular substances (O2, HCl, CO2)
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4
Q

Sodium + Water -> Sodium hydroxide + hydrogen balanced equation

A

2Na(s) + 2H2O(l) -> 2NaOH(s) + H2(g)

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5
Q

Iron(III) oxide + Carbon -> Iron + Carbon dioxide balanced equation

A

2Fe2O3(s) + 3C(s) -> 4Fe(s) + 3CO2(g)

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6
Q

Aluminium + Nitric acid -> aluminium nitrate + hydrogen balanced equation

A

Al(s) + 3HNO3(aq) -> Al(NO3)3(aq) + 1.5H2(g)

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7
Q

compare the amounts of substance in both beakers

A
  • twice as many C atoms needed to make up 12g compared to Mg
  • each C atom has half the mass of a Mg atom
  • same mass doesn’t mean same number of particles
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8
Q

Avogadro constant definition

A

the number of atoms in 12g of 12C

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9
Q

molar mass unit

A

g mol-1

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10
Q

number of particles in: 1 mole of Sodium Na+

A

6.022x10^23 ions of Na

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11
Q

number of particles in: 2 moles of Silicon Si

A

2 x (6.022x10^23) atoms of Si

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12
Q

number of particles in: 1 mole of hydrogen (H2) molecules

A

6.022x10^23 molecules of H2

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13
Q

number of particles in: 3 moles of ammonia (NH3)

A

3 x (6.022x10^23) molecules of NH3

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14
Q

how many atoms of H are in 2 moles of H2O

A

4 moles

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15
Q

number of particles equation

A

Number of particles = Moles x Avogadro Number

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16
Q

relative atomic mass (Ar) definition

A

(average mass of 1 atom of an element) / (1/12th the mass of 12C atom)

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17
Q

relative molecular mass (Mr) definition

A

(average mass of 1 molecule) / (1/12th the mass of 12C atom)

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18
Q

moles equation

A

n = M / Mr

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19
Q

mass unit

A

kg

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20
Q

moles unit

A

mol

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21
Q

concentration equation

A

c = n / V

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22
Q

concentration unit

A

mol dm^-3

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23
Q

volume unit

A

dm^3

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24
Q

1cm^3 to 1dm^3

A

divide by 1000

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25
Q

1dm^3 to 1cm^3

A

multiply by 1000

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26
Q

stage 1 of practical aspects of titrations (steps to make up a standard solution)

A

Transfers know mass of solid
- weigh the sample bottle containing the solid on a (2dp) balance
- transfer the beaker and reweigh sample bottle
- record the difference in mass

27
Q

stage 2 of practical aspects of titrations (steps to make up a standard solution)

A

Dissolves in water
- add distilled / deionised water
- stir (with a glass rod) or swirl
- until all solid has dissolved

28
Q

stage 3 of practical aspects of titrations (steps to make up a standard solution)

A

Transfer, washing and agitation
- transfer to volumetric / graduated flask using a funnel
- with washings
- make up to 250cm^3 / mark with water
- shakes / inverts / mixes

29
Q

why remove any air bubbles from the burette tap

A

otherwise the volume of the air bubble will be counted in the burette reading (GREATER TITRE)
(remove by opening tap first)

30
Q

why remove the funnel used to fill the burette before starting the titration

A

solution drops could fall from the funnel into the burette and affect the burette reading (TITRE DECREASES)

31
Q

why during the titration, swirl the conical flask and rinse the walls of the conical flask with distilled water

A
  • ensures all reactants mix and no reagent is left unreacted on sides of flask
  • doesn’t change the number of moles in conical flask so has no adverse effect on titration
32
Q

% error (uncertainty) equation

A

(error of the equipment / amount measured) x 100

33
Q

how does the error of the equipment change

A

error * (X -> depends on equipment used)
- burette read twice so 2x error

34
Q

how would you decrease % error in a titre measurement

A

increase the measurement made from the burette
- increase the concentration of solution in conical flask
- decrease the concentration of solution in burette

35
Q

the ideal gas equation

A

PV = nRT

36
Q

name P and it’s units in the ideal gas equation

A

pressure
Pa (pascals)

37
Q

name V and it’s units in the ideal gas equation

A

volume
m^3

38
Q

name n and it’s units in the ideal gas equation

A

moles
mol

39
Q

name R and it’s units in the ideal gas equation

A

gas constant = 8.31
J K^-1 mol^-1

40
Q

name T and it’s units in the ideal gas equation

A

temperature
K (kelvin)

41
Q

rearrange PV = nRT for P

A

P = nRT / V

42
Q

rearrange PV = nRT for V

A

V = nRT / P

43
Q

rearrange PV = nRT for n

A

n = PV / RT

44
Q

rearrange PV = nRT for R

A

R = PV / nT

45
Q

rearrange PV = nRT for T

A

T = PV / nR

46
Q

dm^3 to m^3

A

divide by 1000

47
Q

m^3 to dm^3

A

multiply by 1000

48
Q

cm^3 to m^3

A

divide by 1 x 10^6

49
Q

m^3 to cm^3

A

multiply by 1 x 10^6

50
Q

°C to K

A

+ 273

51
Q

K to °C

A
  • 273
52
Q

0°C is ?K

A

273

53
Q

25°C is ?K

A

298

54
Q

100°C is ?K

A

373

55
Q

empirical formula definition

A

the empirical formula of a compound is the simplest whole number ratio of atoms of each element

56
Q

molecular formula definition

A

the molecular formula of a compound is the actual number of atoms of each element

57
Q

how do you remove all the water (water of crytalisation)

A

heat to constant mass

58
Q

atom economy equation

A

% atom economy = (mass of desired products) / (total mass of reactants) x 100

59
Q

why is it desirable to have a high atom economy yield

A
  • increases the mass of atoms in the reactants that are turned into products
  • reduces the amount of waste by-products
60
Q

how can atom economy be improved

A

atom economy can only be improved by finding a different reaction to produce the desired product which also produces fewer by products

61
Q

what is the atom economy if only 1 product is produced

A

100%

62
Q

percentage yield equation

A

(actual yield x 100) / theoretical yield

63
Q

when using a chemical reactant to prepare to prepare a substance it is desirable to have a high % yield because:

A
  • increases the amount of product that is made from the reactants
  • % yield can be increased by making improvements in experimental technique

Separate Chemistry (8 decks)

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