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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
What are the properties of giant metallic substances?
high melting/boiling point insoluble good conductors- delocalised e- good conductor when molten shiny metal malleable
26
What is the trend of melting and boiling points across period?
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
27
What occurs the melting point down group 2 ?
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
28
Does reactivity increase of decrease down group 2?
increases atomic radius increases more shielding nuclear attraction decreases easier to remove outer e- cations form more easily
29
What is common in group 2 electron configuration?
the outer shell has a s2 configurations loss of these e- in redox reactions forms 2+ ions
30
What does group 2 metal and oxygen produce?
metal oxides 2Mg + O2 = 2MgO MgO = white solid group 2 metals burn in oxygen
31
What does group 2 metal and water produce?
steam = metal oxide and hydrogen (Mg only) warm water = meta hydroxide and hydrogen (Mg only) cold water = metal hydroxide and hydrogen
32
What would you observe when group 2 metals react with water to produce hydroxides?
fizzing (increases down group) metal dissolving (faster down group) solution heating up (more down group)
33
What does a group 2 metal and acid produce?
salt and hydrogen
34
What is a use for Ca(OH)2?
agriculture - neutralise acid in soils too much = too alkaline to allow plant growth
35
What is a use of Mg(OH)2 and CaCO3?
as antacids in treating indigestion
36
What do group 2 oxides and water form?
hydroxides the oxides are basic as the ions accept H+ to become hydroxide ions
37
What is the pH of calcium hydroxide?
strong alkaline - pH 12
38
What is the pH of magnesium hydroxide?
partially soluble in water some hydroxide ions will dissolve pH9
39
What can calcium hydroxide also be used in to test...
for presence of carbon dioxide when presence as a aqueous solution = lime water turns cloudy as calcium carbonate is produced
40
What do the halogens exist as?
diatomic molecules
41
What is the state of fluorine at room temp?
very pale yellow gas - highly reactive
42
What is the state of chlorine at room temperature?
green gas - poisonous at high conc
43
What is the state of bromine at room temp?
red liquid/ oranage dissolved in water
44
What is the state of iodine at room temp?
shiny grey solid - purple gas
45
What is the trend in the melting/boiling point down the halogens?
increased down the group; molecules become larger - more electrons; more LDF between molecules; more energy required to break LDF
46
What is the outer shell configuration of the halogens?
s2 p5 form 1- in redox reactions
47
What is the trend of reactivity down the halogen group?
decreases down the group; atoms get bigger with more shieling; less attract and accept electrons; less easily form 1- ions down the group;
48
How do displacement reactions occur in halogens?
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
What is the observation when chlorine reacts with potassium bromine (aq) ?
yellow solution chlorine has displace bromine yellow if organic solvent
50
What is the observation when chlorine reacts with potassium iodide?
brown solution chlorine displaced iodine purple if organic solvent
51
What observation is when bromine reacts with potassium iodide?
brown solution Br has displaced iodine purple if organic solvent
52
Explain why chlorine is more reactive than bromine and iodine?
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
What is meant by the term disproportionation?
a reaction where an element simultaneously oxidises and reduces
54
What happens when chlorine reacts with water?
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
What is chlorine used as in the real world?
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
What happens when chlorine reacts with cold dilute NaOH?
disproportionation reaction; Cl2 + 2NaOH = NaCl +NaClO + H2O
57
What is the mixture of NaClO and NaCl used for?
bleach to kill bacteria
58
What is used to identify halide ions?
silver nitrate solution (nitric acid and silver nitrate added dropwise)
59
What is the role of nitrates in silver nitrate?
react with any carbonates to prevent formation of the precipitate Ag2Co3 = mask observations
60
What observation is seen when silver nitrate reacts with fluoride ions?
no ppt formed
61
What observation is seen when silver nitrate reacts with chloride ions?
white precipitate Ag+ + Cl- = AgCl (s)
62
What observation is seen when silver nitrate reacts with bromide ions?
cream precipitate Ag+ + Br- + AgBr (s)
63
What observation is seen when silver nitrate reacts with iodine ions?
yellow precipitate Ag+ + I- = AgI (s)
64
Silver chloride dissolves in....
dilute ammonia
65
Silver bromide dissolves in....
conc ammonia
66
Silver iodine dissolves in...
DOESNT DISSOLVE/REACT WITH AMMONIA = insoluble
67
What is the order of tests for qualitative analysis?
carbonate sulfate halide (BaCO3 and Ag2SO4 are both insoluble - mask observations)
68
How do you test for a carbonate?
add any dilute acid = observe effervescence bubble gas through lime water = cloudy 2HCl +Na2CO3 = 2NaCL + H2O + CO2
69
How do you test for sulfates?
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
How do you test for ammonium ions?
warm NaOH form NH3 gas pungent smell/ damp red litmus paper blue

OCR A-Level Chemistry (4 decks)

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