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chem > topic 5: formulae, equations and amounts of substance > Flashcards

topic 5: formulae, equations and amounts of substance Flashcards

(51 cards)

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1
Q

mole is

A

unit for amount of a substance
same no. of particles as there are atoms in 12g of 12C

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2
Q

avogadros constant

A

6.02 x 10^23 mol-1

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3
Q

molar mass

A

mass of 1 mole of substance in g/mol

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4
Q

ideal gas equation

A

pV = nRT
pressure = pa
V = m3
n= mol
R= gas constant (data book)
T = kelvin

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5
Q

conc =

A

mol/vol

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6
Q

(dm3)vol (gas)=

A

mol/24
ROOP TEMP AND PRESSURE

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7
Q

molecular formula

A

shows number and type of each atom in a. molecule

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8
Q

empirical formula

A

simplest whole number ratio of the elements present in one molecule of a compound

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9
Q

celcius to kelvin

A

add 273

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10
Q

relative atomic mass

A

average mass of one atom compared to the mass of 1/12 of c-12 atom

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11
Q

relative isotopic mass

A

mass of an isotope compared to the mass of 1/12 of c-12 atom

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12
Q

mol, mass , mr

A

mol = mass/mr

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13
Q

1 tonne

A

1000kg

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14
Q

water of crystallisation experiment is done by …

A

heating in a crucible

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15
Q

heating in a crucible experiment method

A
  • weigh an empty can dry crucible + lid
  • add 2g of hydrated and reweigh
  • heat strongly
  • cool
  • reweigh
  • heat and reweigh until a constant mass
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16
Q

what happens if the crucible is wet

A
  • mass loss too large as water lost when heating
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17
Q

purpose of lid in crucible

A
  • prevents loss of solid but still lets gas out
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18
Q

why not use tiny masses of solid in crucible experiment

A

errors in weighing too high

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19
Q

calculation from the crucible experiment

A
  • moles anhydrous salt
  • moles water
  • divide by smallest and find ratio
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20
Q

no. particles, mol, AC

A

particles = mol*AC

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21
Q

density equation

Study These Flashcards
A

mass/ vol
g/cm3

22
Q

M unit of conc

23
Q

how to go from moldm-3 to gdm-3

Study These Flashcards
A

multiply by the Mr

24
Q

making a standard solution

Study These Flashcards
A
  • weigh mass by difference
  • transfer mass to beaker
  • add distilled water, use a glass rod to store
  • pour through funnel into volumetric flask
  • washings
  • make up to the mark and invert so its UNIFORM
  • bottom of meniscus
25
what does diluting change
NOT moles of solute but increases the vol so conc is lower
26
how to calc diluted conc
CONSTANT MOLES SO og conc * og vol = new conc * new vol
27
what to remember with volumes in concentrations
add / subtract the ORIGINAL when they're asking how much new
28
mixture of gases moles with ideal gas equation
n is the total moles of all gases in the mixture
29
errors in gas syringe (3)
- friction - use a lubricant - gas escapes before bung inserted - use the vial - some gases are soluble in water so true amount isn't measured
30
reacting volumes of gases
- same at room temp
31
reading
SINGLE judgement- one reading
32
measurement
DIFFERENCE between 2 readings
33
uncertainty is
at least +- 0.5 of the smallest scale reading
34
how to decrease uncertainty
- use apparatus with a greater resolution - increase the size of the measurement made
35
balance uncertainty
0.001
36
volumetric flask uncertainty
0.1
37
25cm3 pipette unceratinty
0.1
38
burette uncertainty
0.05
39
% uncertainty
uncertainty/measurement * 100
40
% uncertainty vs percentage diff in the measured and real value
- if % of equipment is less than the measured and real, there are other errors - if % of equipment is greater than measured and real, no other errors
41
% yield
actual yield/theoretical yield * 100
42
factors lowering percentage yield
- incompleet reactions - side reactions - losses during transfer
43
atom economy
mr of useful products / mr of all reactants * 100 USE REACTING RATIO
44
why might economy be lower
reaction not gone to completion
45
reactions with one product has ...
100% atom economy
46
observations with acid + carbonate
- effervescent (CO2) - carboante dissolves - TEMP INCREASE
47
spectator ions
- same state - same oxidation number
48
why must gas be dry
- water vapour affects molar mass
49
reason for vol of gas lower
- gas lost when replacing bung (put mg in a vial so reacts after bung replaced) - magnesium coated in oxide, so water produced instead of H2 (clean it before) - co2 soluble in water - temp lower than room temp (if u used 24)
50
how to know if gas syringe leaky
- plunger doesnt return to 0 when released - mr decreases because air has a lower mr
51
why deos phenolphthalein turn pink in alkali
forms a pink anion by loss of H+ ions

chem (29 decks)

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