Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A - Chemistry > Unit 2: Section 2 - Group 2 and group 7 elements CDS * > Flashcards

Unit 2: Section 2 - Group 2 and group 7 elements CDS * Flashcards

Group 2 - the alkaline earth metals uses of the group 2 elements Group 7 - the halogens halide ions tests for ions

1
Q

how many outer electrons do group 2 elements have?

A

they all have 2 electrons in their outer shell (s2)

they form 2+ ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what happens to atomic radius down group 2?

A

atomic radius increases

more electron shells as you go down group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what happens to 1st ionisation energy down group 2?

A 
more electron shells
more shielding
greater atomic radius
weaker forces of attraction between outer electron and positive nucleus
ionisation energy decreases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what happens to reactivity down group 2?

A

1st ionisation energy decreases
easier to lose electrons to react
reactivity increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the general trend in melting points down group 2?

A

metallic structure
ions get bigger, same number of delocalised electrons
greater distance between delocalised electrons and positive nuclei, so weaker forces of attraction
less energy required to break bonds
melting point decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is a metallic structure?

A

positive ions in crystal structure surrounded by delocalised electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how does the trend in melting points down group 2 differ?

A

magnesium has a different crystal structure (arrangement of the metallic ions changes) so it has the lowest melting point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what happens to oxidation state of group 2 elements when they react?

A

they are oxidised from an oxidation state of 0 to +2
M —-> M2+ + 2e-
0 +2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what happens when group 2 metals react with water?

A

a metal hydroxide and hydrogen is produced

they react more readily down the group as ionisation energies decrease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how does each group 2 element react with water?

A

Be - doesn’t react
Mg - very slowly
Ca - steadily, fizzes and forms white solid
Sr - fairly quickly, fizzes and forms colourless solution
Ba - rapidly, fizzes and forms colourless solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how soluble are group 2 compounds containing singly charged negative ions (hydroxides)?

A

e.g. OH-

solubility increases down the group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how soluble are group 2 compounds containing doubly charged negative ions (sulfates)?

A

e.g. SO4 2-

solubility decreases down the group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what happens to the solubility of group 2 hydroxides down the group?

A 
it increases 
Mg(OH)2 - insoluble
Ca(OH)2 - slightly soluble
Sr(OH)2 - soluble
Ba(OH)2 - soluble
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what happens to the solubility of group 2 sulfates down the group?

A 
it decreases
MgSO4 - soluble
CaSO4 - slightly soluble
SrSO4 - insoluble
BaSO4 - insoluble
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the test for sulfates?

A

add dilute HCl
if acidified barium chloride (BaCl2) is added to a solution containing sulfate ions then a white precipitate of barium sulfate is formed
Ba 2+(aq) + SO4 2-(aq) —> BaSO4(s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are group 2 elements known as?

A

alkaline earth metals, they are often used for neutralising acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what common group 2 compounds are used for neutralising acids?

A 
calcium hydroxide (Ca(OH)2) - aka slaked lime, used in agriculture to neutralise acidic soils
magnesium hydroxide (Mg(OH)2) - used in some indigestion tablets as an antacid
H+(aq) + OH-(aq) --> H2O(l)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is an antacid?

A

a substance that neutralises excess stomach acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is barium sulfate used for?

A

barium sulfate is opaque to X-rays.
its used in barium meals to help diagnose problems with the oesophagus, stomach or intestines
barium sulfate coats the tissues, making them show up in x-rays, showing the structure of the organs
its insoluble so doesn’t damage tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how is magnesium used to extract titanium?

A

titanium(IV) oxide (TiO2) is converted to TiCl4, by heating it with carbon in a stream of chlorine gas
it’s purified by fractional distillation
reduced by magnesium in a furnace at almost 100*C
TiCl4(g) + 2Mg(l) –> Ti(s) +2MgCl2(l)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is wet scrubbing?

A

the process by which acidic sulfur dioxide can be removed from flue gases by reacting with an alkali.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how can calcium be used to remove sulfur dioxide?

A

powdered calcium oxide and calcium carbonate can be used in wet scrubbing.
a slurry is made by mixing CaO or CaCO3 with water. its then sprayed onto the flue gases, producing calcium sulphite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the reaction between calcium oxide or carbonate with sulfur dioxide in flue gases?

A

CaO(s) + 2H2O(l) + SO2(g) —-> CaSO3(s) + 2H2O(l)

CaCO3(s) + 2H2O(l) + SO2(g) —-> CaSO3(s) + 2H2O(l) + CO2(g)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what colour is gaseous fluorine?

A

pale yellow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
what colour is gaseous chlorine?
green
26
what colour is liquid bromine?
orange/red-brown
27
what colour is solid iodine?
grey
28
what is fluorine's physical state?
gas
29
what is chlorine's physical state?
gas
30
what is bromine's physical state?
liquid
31
what is iodine's physical state?
solid
32
what happens to the boiling point of elements down group 7?
they increase the size and relative mass of the molecules increases. so more electrons so van der Waals forces increase
33
what happens to the electronegativity of elements down group 7?
it decreases halogens are highly electronegative larger atoms have more shielding and have a larger atomic radius so have weaker forces of attraction between the nucleus and the shared electron pair
34
what is electronegativity?
the tendency of an atom to attract a bonding pair of electrons
35
what happens to reactivity down group 7?
it decreases atoms are larger outer shell further from the nucleus so weaker FOA
36
what happens to oxidising ability down group 7?
it decreases atoms are larger more shielding harder to gain electrons
37
what is the rule for how halogens displace?
a halogen will displace a halide from solution if the halide is below it in the periodic table
38
how can displacement reactions be used to identify which halogen is present in a solution?
if a more reactive halogen displaces another, the halogen that is displaced is then present, and whatever colour it is will be the colour observed e.g. colourless KBR reacts with Cl2 to form KCl and Br which will form an orange solution
39
what happens when you mix chlorine with cold, dilute, aqueous sodium hydroxide?
you get sodium chlorate(I) solution (NaClO) which is bleach 2NaOH(aq) + Cl2(g) --> NaClO(aq) +NaCl(aq) +H2O(l) oxidaton state of chlorine is both higher and lower - disproportionation
40
what is bleach used for?
water treatment to bleach paper and textiles cleaning, killing bacteria
41
what happens when chlorine is mixed with water?
it undergoes disproportionation, and the product consists of a mixture of chloride and chlorate(I) ions chlorine can decompose water in sunlight to form chloride ions and oxygen Cl2 + H2O HCl +HClO
42
how does chlorine kill bacteria in water?
chlorate(I) ions kill bacteria. so adding chlorine to water can make it safe to drink or swim in, but chlorine is toxic
43
how is chlorine an important part of water treatment?
it kills disease-causing microorganisms some chlorine persists in water and prevents reinfection prevents growth of algae, eliminating bad tastes and smells removes discolouration caused by organic compounds
44
what risks are involved in using chlorine to treat water?
chlorine gas is very harmful | water reacts with organic compounds in water to form chlorinated hydrocarbons
45
how is chlorine gas harmful?
irritates respiratory system if breathed in | liquid chlorine on skin or eyes causes severe chemical burns
46
how are chlorinated hydrocarbons harmful?
many are carcinogenic, but the increased risk of cancer is small compared to risks from untreated water
47
what happens to the reducing power of halides down the group?
increases ions get bigger, electrons further away from positive nucleus extra inner electron shells, so more shielding weaker FOA, easier to lose electrons to act as a reducing agent
48
what happens when NaF or NaCl reacts with H2SO4?
NaHSO/ Na2SO4 formed HF or HCl is formed misty fumes are observed not a redox reaction
49
what happens when NaBr reacts with H2SO4?
``` HBr formed misty fumes observed HBr is a strong reducing agent so reacts with H2SO4 in a redox reaction SO2, choking fumes produced orange Br2 fumes produced ```
50
what happens when NaI reacts with H2SO4?
``` misty HI fumes produced HI reduces H2SO4 choking SO2 and purple I2 fumes produced HI reduces SO2 H2S formed - toxic, smells of rotten eggs solid iodine formed ```
51
what is the test for halides?
dissolve in water add dilute nitric acid to remove ions that might interfere with test add few drops of silver nitrate solution (AgNO3) silver halide precipitate formed add ammonia solution (NH3), each silver halide has different solubilities in ammonia
52
what coloured precipitates do each halide produce in test for halides with AgNO3?
fluoride - no precipitate chloride - white precipitate bromide - cream precipitate iodide - yellow precipitate
53
what happens to different silver halides in ammonia?
chloride - white precipitate dissolves in dilute NH3 bromide - cream precipitate dissolves in concentrated NH3 iodide - yellow precipitate is insoluble in NH3
54
how to use flame tests to identify group 2 ions?
dip a nichrome wire loop in concentrated hydrochloric acid dip wire loop into unknown compound hold loop in the clear blue part of a Bunsen burner flame observe colour change
55
what colour flame do different group 2 ions burn?
calcium - brick red strontium - red barium - pale green
56
how can you use NaOH to identify group 2 ions?
dissolve in water add NaOH dropwise to a test tube containing the metal ion solution observe the precipitate that forms keep adding NaOH until it is excess, record any changes you see
57
what precipitates form from mixing halide ions with NaOH?
magnesium (Mg(OH)2) - slight white precipitate, white precipitate with excess calcium (Ca(OH)2) - slight white precipitate, slight white precipitate strontium (Sr(OH)2) - no change(colourless solution), slight white precipitate barium (Ba(OH)2) - no change, no change
58
how can you test for ammonia gas using litmus paper?
ammonia gas is alkaline, so it can be tested for using a damp piece of red litmus paper, it will turn blue if ammonia is present
59
how can you test for ammonium ions using NaOH?
if hydroxide ions in NaOH are added to a solution containing ammonium ions, ammonia gas and water is produced NH4+ + OH- --> NH3 +H2O ammonia can then be tested for
60
how can you test for sulphates using HCl and barium chloride?
add dilute HCl add barium chloride solution if a white precipitate of barium sulfate forms, sulfate was present
61
how can you test for hydroxides using indicator?
hydroxide ions make solutions alkaline, so a pH indicator should reflect this if hydroxide ions are present
62
how to test for halides using silver nitrate?
``` dissolve in water add dilute nitric acid then silver nitrate solution fluorine - colourless solution chlorine forms white precipitate bromide gives cream silver bromide iodide gives yellow silver iodide ```
63
how to test for carbonates using HCl?
add dilute HCl if solution contains carbonate ions it will fizz as carbon dioxide is released CO3 2- + 2H+ --> CO2 + H2O then carbon dioxide can be tested for
64
how to test for carbon dioxide?
using limewater CO2 turns limewater cloudy bubble the gas through a test tube of limewater, and observe is limewater goes cloudy
65
what happens to atomic radius down group 7?
increases more electron shells so bigger atoms
66
what happens to 1st ionisation energy down group 7?
decrease atoms get bigger more shielding weaker attraction from nucleus to electron in outer shell
67
what colour is chlorine water?
colourless
68
what colour is bromine water?
orange
69
what colour is iodine solution?
brown
70
what are halogens known as?
salt makers e.g. NaCl
71
How to test for group 2 ions?
using H2SO4 | using NaOH
72
how to test for group 2 ions using H2SO4?
dissolve ions in water add H2SO4 group 2 sulfates have different solubilities so observe solutions for changes
73
what precipitates do group 2 sulfate ions form?
MgSO4 - very soluble - colourless solution CaSO4 - soluble - colourless solution SrSO4 - slightly soluble - white precipitate BaSO4 - insoluble - white precipitate
74
what colour are iodine fumes?
purple

A - Chemistry (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions