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OCR A-Level Chemistry > Module 3.1 > Flashcards

Module 3.1 Flashcards

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1
Q

How is the periodic table arranged?

A

increasing proton number

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2
Q

What do elements in the same groups have in common?

A

similar physical properties
similar chemical properties
same no. of electrons on the outer shell

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3
Q

What do elements in the same periods show?

A

show repeating trends in physical and chemical properties

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4
Q

Elements are in the s, p, d or f block because…

A

the orbital with the highest energy with electrons is in that subshell

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5
Q

What is periodicity?

A

repeating patterns of trend across different periods

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6
Q

What happens to the atomic radius across a period 2 and 3?

A

atomic radius decreases
increased proton number
similar shielding
electrons on the same shell
increased nuclear attraction between nucleus and out electron

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7
Q

What is first ionisation energy?

A

energy required to remove one mole of electrons from one mole of gaseous atoms
H (g) -> H+ (g) + e-
remember state symbol

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8
Q

What are the three factors the affect ionisation energy?

A

attraction to nucleus
(more protons more nuclear attraction)
distance of electrons from nucleus
(bigger distance weaker attraction
shielding of electron from nucleus
(outer e- is repelled by inner shell e- = weakeing attraction of nucleus)

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9
Q

Why are successive energies always larger than first?

A

the ion formed is smaller than the atom
proton to electron ration in the 2+ ion is greater than the 1+
attraction between nucleus and electron is therefore stronger
requires more energy to remove electron

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10
Q

How can you use successive ionisation energies to work out what group element is in?

A

the biggest jump e.g between 2nd and 3rd
element must be in group 2
as the 3rd electron is removed from an electron shell closer to the nucleus
with less shielding and more nuclear attraction
= larger ionisation energy

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11
Q

Why has helium got the largest first IE?

A

first electron is in the first shell closest to the nucleus
no shielding effect from inner shells
bigger IE than H as it has one more proton

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12
Q

Why do first IE decrease down a group?

A

proton number increases BUT
increased shielding
bigger atomic radius
weaker nuclear attraction

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13
Q

Why is there a general increase in first IE across a period?

A

electrons added on to same shell/similar shielding
proton number increases
smaller atomic radius
increased nuclear attraction

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14
Q

Why has Na have a much lower first IE than neon?

A

Na has it outer electrons on a 3s subshell - more further away from nucleus than Ne 2p subshell
less nuclear attraction

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15
Q

Why is there a small drop in IE from Mg to Al?

A

Al is starting to fill 3p subshell
Mg outer shell electron on 3s subshell
electrons in the 3p subshell are easier to remove = higher energy and shielded by 3s electrons

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16
Q

Why is there a small drop in IE from P to S?

A

in sulphur there are 4 electrons in the 3p subshell; 4th pairing doubly
second electron added to 3p orbital = slight repulsion between the two negative electrons = makes electrons easier to remove

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17
Q

What is metallic bonding?

A

electrostatic force of attraction between positive metal ions and the delocalised electrons

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18
Q

What are the factors that affect the strength of metallic bonding?

A

number of protons
number of delocalised electrons per atom
size of ion (smaller = stronger)

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19
Q

Explain why Mg has a higher melting point than Na?

A

Mg has stronger metallic bonding than Na;
the metallic bonding gets stronger because in Mg there are more electrons in the outer shell that are released to the sea of electrons;
the Mg ion is also smaller and has one more proton;
there is a stronger electrostatic force of attraction between the positive metal ion and the delocalised electrons = higher energy needed to break the bonds

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20
Q

What is the structure of metals?

A

giant metallic lattice structure

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21
Q

What is the structure of diamond?

A

4 covalent bonds per atom
tetrahedral
macromolecular
carbon

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22
Q

What is the structure of graphite?

A

trigonal planar arrangement of carbon
3 covalent bonds per atom in each layer
4th outer electron per atom delocalised
delocalised electrons between layers

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23
Q

Why do diamond and graphite have high melting points?

A

strong covalent bonds
in giant molecular structures
takes lots of energy to break many strong covalent bonds

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24
Q

What are the properties of macromolecular substances?

A

high melting/boiling points
insoluble
diamond cannot conduct
graphite can = free delocalised e-
poor conduction when molten
solids

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25
Q

What are the properties of giant metallic substances?

A

high melting/boiling point
insoluble
good conductors- delocalised e-
good conductor when molten
shiny metal
malleable

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26
Q

What is the trend of melting and boiling points across period?

A

metallic - covalent - simple molecule

Na, Mg, Al - metallic - strong bonding - gets stronger the more e- there are in the outer shell that are released to the sea of e-

Si - macromolecular - many strong covalent bonds = high mp/bp

Cl2, S8, P4 - weak LDP between molecules = little energy needed to break

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27
Q

What occurs the melting point down group 2 ?

A

decreases;
metallic bonding weakens as the atomic size increases
the distance between the positive ions and the delocalised e- increases
the attractive forces between the positive ions and delocalised electrons weakens

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28
Q

Does reactivity increase of decrease down group 2?

A

increases
atomic radius increases
more shielding
nuclear attraction decreases
easier to remove outer e-
cations form more easily

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29
Q

What is common in group 2 electron configuration?

A

the outer shell has a s2 configurations
loss of these e- in redox reactions forms 2+ ions

30
Q

What does group 2 metal and oxygen produce?

A

metal oxides

2Mg + O2 = 2MgO

MgO = white solid

group 2 metals burn in oxygen

31
Q

What does group 2 metal and water produce?

A

steam = metal oxide and hydrogen (Mg only)
warm water = meta hydroxide and hydrogen (Mg only)
cold water = metal hydroxide and hydrogen

32
Q

What would you observe when group 2 metals react with water to produce hydroxides?

A

fizzing (increases down group)
metal dissolving (faster down group)
solution heating up (more down group)

33
Q

What does a group 2 metal and acid produce?

A

salt and hydrogen

34
Q

What is a use for Ca(OH)2?

A

agriculture - neutralise acid in soils
too much = too alkaline to allow plant growth

35
Q

What is a use of Mg(OH)2 and CaCO3?

A

as antacids in treating indigestion

36
Q

What do group 2 oxides and water form?

A

hydroxides
the oxides are basic as the ions accept H+ to become hydroxide ions

37
Q

What is the pH of calcium hydroxide?

A

strong alkaline - pH 12

38
Q

What is the pH of magnesium hydroxide?

A

partially soluble in water
some hydroxide ions will dissolve
pH9

39
Q

What can calcium hydroxide also be used in to test…

A

for presence of carbon dioxide
when presence as a aqueous solution = lime water
turns cloudy as calcium carbonate is produced

40
Q

What do the halogens exist as?

A

diatomic molecules

41
Q

What is the state of fluorine at room temp?

A

very pale yellow gas - highly reactive

42
Q

What is the state of chlorine at room temperature?

A

green gas - poisonous at high conc

43
Q

What is the state of bromine at room temp?

A

red liquid/ oranage dissolved in water

44
Q

What is the state of iodine at room temp?

A

shiny grey solid - purple gas

45
Q

What is the trend in the melting/boiling point down the halogens?

A

increased down the group;
molecules become larger - more electrons;
more LDF between molecules;
more energy required to break LDF

46
Q

What is the outer shell configuration of the halogens?

A

s2 p5
form 1- in redox reactions

47
Q

What is the trend of reactivity down the halogen group?

A

decreases down the group;
atoms get bigger with more shieling;
less attract and accept electrons;
less easily form 1- ions down the group;

48
Q

How do displacement reactions occur in halogens?

A

a halogen that is more reactive (higher on the periodic table) will displace a halogen that has lower reactivity from one of its compounds

49
Q

What is the observation when chlorine reacts with potassium bromine (aq) ?

A

yellow solution
chlorine has displace bromine
yellow if organic solvent

50
Q

What is the observation when chlorine reacts with potassium iodide?

A

brown solution
chlorine displaced iodine
purple if organic solvent

51
Q

What observation is when bromine reacts with potassium iodide?

A

brown solution
Br has displaced iodine
purple if organic solvent

52
Q

Explain why chlorine is more reactive than bromine and iodine?

A

down the group there is decreasing ease in forming 1- ions;
chlorine will gain an electron and form a negative ion more easily than bromine;
atom of chlorine is smaller and the outer shell electrons are less shielded than bromine;
more nuclear attraction so electron gained is attracted more strongly to the nucleus in chlorine than bromine

53
Q

What is meant by the term disproportionation?

A

a reaction where an element simultaneously oxidises and reduces

54
Q

What happens when chlorine reacts with water?

A

Cl2 + H2O -> HClO + HCl

if indicator is added - turn red due to HClO and HCl acidity
but then it would turn colourless as HClO will bleach the colour

55
Q

What is chlorine used as in the real world?

A

water treatment facilities
to kill bacteria
treat drinking water/swimming pools
benefits of water treatment by killing its bacteria outweigh the risk of toxic effects and the possible risks for formation of chlorinated hydrocarbons

56
Q

What happens when chlorine reacts with cold dilute NaOH?

A

disproportionation reaction;
Cl2 + 2NaOH = NaCl +NaClO + H2O

57
Q

What is the mixture of NaClO and NaCl used for?

A

bleach to kill bacteria

58
Q

What is used to identify halide ions?

A

silver nitrate solution
(nitric acid and silver nitrate added dropwise)

59
Q

What is the role of nitrates in silver nitrate?

A

react with any carbonates to prevent formation of the precipitate Ag2Co3 = mask observations

60
Q

What observation is seen when silver nitrate reacts with fluoride ions?

A

no ppt formed

61
Q

What observation is seen when silver nitrate reacts with chloride ions?

A

white precipitate
Ag+ + Cl- = AgCl (s)

62
Q

What observation is seen when silver nitrate reacts with bromide ions?

A

cream precipitate
Ag+ + Br- + AgBr (s)

63
Q

What observation is seen when silver nitrate reacts with iodine ions?

A

yellow precipitate
Ag+ + I- = AgI (s)

64
Q

Silver chloride dissolves in….

A

dilute ammonia

65
Q

Silver bromide dissolves in….

A

conc ammonia

66
Q

Silver iodine dissolves in…

A

DOESNT DISSOLVE/REACT WITH AMMONIA
= insoluble

67
Q

What is the order of tests for qualitative analysis?

A

carbonate
sulfate
halide

(BaCO3 and Ag2SO4 are both insoluble - mask observations)

68
Q

How do you test for a carbonate?

A

add any dilute acid = observe effervescence
bubble gas through lime water = cloudy

2HCl +Na2CO3 = 2NaCL + H2O + CO2

69
Q

How do you test for sulfates?

A

add acidified barium chloride/ions
white precipitate forms - barium sulfate

sulfuric acid cannot be used to acidify = sulfate ions present = would form ppt

acid added to react with carbonate impurities - white ppt of barium carbonate

70
Q

How do you test for ammonium ions?

A

warm NaOH form NH3 gas
pungent smell/ damp red litmus paper blue

OCR A-Level Chemistry (4 decks)

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