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A-Level Chemistry > 2.1 Atoms and reactions > Flashcards

2.1 Atoms and reactions Flashcards

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1
Q

isotope definition

A

atoms of the same element but with different number of neutrons and mass number

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2
Q

atomic mass number

A

number of protons and neutrons in nucleus of an atom

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3
Q

atomic number

A

number of protons in nucleus

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4
Q

relative mass of electron

A

1/1836

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5
Q

relative isotopic mass definition

A

mass compared with 1/12th mass of carbon-12

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6
Q

relative atomic mass definition

A

weighted mean mass compared with 1/12th mass of carbon-12

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7
Q

relative formula mass used for

A

compounds with giant structures

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8
Q

relative molecular mass used for

A

simple molecules

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9
Q

mole (mol)

A

unit for amount of substance

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10
Q

Avogadro constant (NA)

A

number of particles per mole

6.02 x10^23 mol^-1

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11
Q

molar mass

A

mass per mole

g mol^-1

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12
Q

molar gas volume

A

gas volume per mole

units dm^3 mol^-1

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13
Q

empirical formula

A

simplest whole number ratio of atoms of each element in a compound

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14
Q

molecular formula

A

number and type of atoms of each element in a molecule

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15
Q

relationship between moles, mass and Ar

A

mass (g) = Ar x moles (mol)

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16
Q

relationship between concentration, volume and moles

A

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

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17
Q

relationship between Ar, moles, ideal gas constant, pressure, temperature and volume

A

Moles (n) = pressure (Pa) x volume (dm^3) / ideal gas constant (8.3145 J K^-1 mol^-1) x temperature (K)

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18
Q

relationship between moles, molar gas volume and volume in RTP and normal pressures

A

moles = volume (dm^3) x 24 (dm^3)

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19
Q

anhydrous definition

A

without water

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20
Q

water of crystallisation definition

A

water bonded into a crystalline structure

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21
Q

degree of hydration definition

A

number of moles of water of crystallisation chemically bonded in 1 mole of the compound

22
Q

hydrated definition

A

crystalline structure containing water molecule

23
Q

standard / stock solution definition

A

solution of known concentration

24
Q

stoichiometry definition

A

ratio of moles of each substance

25
Q

why theoretical yield is not achieved

A

reaction not gone to completion
side reactions may have occurred
purification of production may result in loss of product

26
Q

theoretical yield definition

A

maximum possible amount of product of a reaction

27
Q

actual yield definition

A

actual amount of product of a reaction

28
Q

percentage yield

A

conversion of starting materials into desired product

29
Q

percentage yield formula

A

percentage yield (%) = actual yield / theoretical yield x 100%

30
Q

limiting reagent definition

A

reactant completely used up first and stops reaction (e.g. not in excess)

31
Q

atom economy definition

A

measure of how well atoms have been utilised

32
Q

important of high atom economy reactions

A

large proportion of desires products to unwanted waste products
sustainable as make the best use of natural resources

33
Q

atom economy formula

A

atom economy = (sum of molar masses of desired products / sum of molar masses of all products )x 100%

34
Q

acid definition

A

proton donor

35
Q

strong acid definition

A

acid that completely dissociates (releases all hydrogen atoms) in aqueous solution

36
Q

weak acid definition

A

acid that partially disassociates (releases small proportion of hydrogen) in aqueous solution

37
Q

base definition

A

substance that neutralises acid to form a salt

e.g. metal (hydr)oxides, metal carbonates and ammonia

38
Q

alkali definition

A

base that releases hydroxide ions into solution

39
Q

titration definition

A

technique used to accurately measure the volume of one solution that reacts exactly with another solution

40
Q

titration uses

A

finding concentration of a solution
identification of unknown chemicals
finding purity of a substance

41
Q

how to prepare standard solution

A

solid weighed accurately and dissolved in beaker using distilled water (less than will be needed to fill volumetric flask)
solution transferred to volumetric flask
rinse traces of solution using distilled water into flask
add distilled water until bottom of meniscus lines up with graduation line
invert flask multiple times to mix solution properly
careful of parallax error

42
Q

acid-base titration procedure

A

add measured volume of one solution using pipette into conical flask
add other solution fo burette and record initial burette reading
add few drops on indicator to conical flask
slowly add solution in burette to conical flask while stirring until indicator changes colour
colour change = end point = volume of one solution that reacts exactly with other solution
titre calculated by subtracting final burette reading from initial burette reading
repeat until two accurate tires are concordant

43
Q

end point definition

A

indicates volume of one solution exactly reacting with another

44
Q

titre definition

A

volume of solution added from burette

subtract final burette reading from initial burette reading

45
Q

concordant definition

A

agreeing to within 0.10 cm^3

46
Q

reduction definition

A

gain of electrons

decrease in oxidation number

47
Q

oxidation reaction

A

loss of electrons

decrease in oxidation number

48
Q

redox reaction definition

A

reaction containing both reduction and oxidation

49
Q

how to measure water of crystallisation

A

weigh empty crucible
add hydrated salt to crucible, weigh crucible again
heat using pipe-clay triangle to support crucible on tripod
heat for period of time
remove crucible, allow to cool (too hot affects mass reading) and reweigh
heat crucible for further period of time (until recorded constant mass)

50
Q

problems in water of crystallisation practical

A

not all water lost -> heat until constant mass recorded

compound decomposes further (heated too much) -> heat gently, slowly, removing from heat periodically

A-Level Chemistry (12 decks)

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