C8- Reactivity trends Flashcards

1
Q

Why can group 2 alkaline metals be called reducing agents

A

The group 2 agent reduces another species

Another species will gain the two electrons and be reduced

Group 2 agent itself is reduced

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2
Q

Reaction of group 2 with oxygen

A

Always forms metal oxides

e.g. MgO, CaO

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3
Q

Reaction of group 2 with water

A

Forms an alkaline hydroxide and hydrogen gas

Forms OH- ions in solution

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4
Q

Reactivity down group 2

A

Increases down the group

Increased shielding
Increased atomic radius
Decreased nuclear attraction
Less energy need to remove outer e-

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5
Q

First ionisation energy down group 2

A

Decreases down the group

Reduced nuclear attraction as a result of increased shielding and decreased atomic radius

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6
Q

Group 2 oxides in water

A

Release OH- ions into solution
–> forming an alkaline solution of metal hydroxide

If oversaturated further metal or OH- ions will be precipitated into solution

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7
Q

Solubility of group 2 hydroxides in water

trend + explanation

A

increases down the group

resulting solutions are more alkaline

Thus alkalinity increases down the group

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8
Q

2 uses of group 2 compounds as bases

A

Agriculture- CaOH2 increases the pH of acidic soil, neutralising it and producing neutral water

Medicine- Antacids or indigestion, as it neutralises the HCl form the stomach

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9
Q

Physical properties of halogens

A

Don’t occur in elemental form in nature

E.g. salt or dissolved in oceans

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10
Q

Boiling point of halogens

trend + explanation

A

Increases down the group

More electrons
stronger London forces
More energy needed to break intermolecular forces
Bp increases

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11
Q

Why can halogens be called oxidising agents

A

Another species looses electrons to the halogens, oxidising it

Halogen oxidises another species

is itself reduced

Fluorine is the strongest oxidising agent

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12
Q

halogens in cyclohexane

A

Dissolve more readily in cyclohexane than in water

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13
Q

Disproportionation reaction

A

Redox reaction were the same element is bot oxidised and reduced

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14
Q

Chlorine in water

reaction + bacteria

A

Disproportionation reaction that produces HCl and HClO

Its the acids not chlorine tat kills bacteria in the water

Reduces incidence of water borne diseases

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15
Q

Chlorine and cold aqueous sodium hydroxide

A

Chlorine has a low solubility in water

When the water contains dissolves NaOH, much more CL2 then dissolves

Another disproportionation reaction takes place

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16
Q

Benefits and risk of chlorine usage

A

Cl2 is a toxic gas
a respiratory irritant
in large concentrations lethal

Cl2 can react with hydrocarbons, producing carcinogenic chlorinated hydrocarbons.

the overall risk of not using Cl2 is far greater than using it

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17
Q

Carbonate test

A

add acid

positive- forms carbon dioxide gas (bubbles)

typically use nitric acid

18
Q

CO2 test

A

Bubble gas through limewater
–> calcium hydroxide

turns cloudy as calcium carbonate is formed

19
Q

Sulfate test

A

add aqueous barium nitrate or barium chloride

white precipitate forms
–> barium sulfate

20
Q

halide test

A

add aqueous silver nitrate

silver halide precipitate forms

add ammonia to test solubility of precipitate- iodine insoluble but cl and br are soluble

21
Q

Halide test colours

A

Chlorine- white

Bromine- cream

Iodine- yellow

22
Q

correct sequence for anion tests

A

carbonate

sulfate

halide

23
Q

Why must carbonate test be done first

A

reduces chances of incorrect conclusion

only one test produces bubbles

carbonate will also form a white precipitate within the sulfate test

24
Q

Mixture of ions

qualitative tests

A

do carbonate test until no more bubbles- all carbonate ion shave reacted- must use nitric acid not sulfuric acid as about to do sulfate test

use same mixture

filter out barium sulfate- don’t use barium chloride if doing halide test use barium nitrate

25
Q

Test for ammonium

A

heat with a hydroxide

produces ammonia gas- no bubbles as very soluble

Ph will increase as ammonia is alkaline

26
Q

Lithium ion flame

A

red / crimson

27
Q

Sodium ion flame

28
Q

Potassium ion flame

29
Q

calcium ion flame

A

orange-red

30
Q

copper ion flame

A

blue-green

31
Q

Aluminium ion in Naoh test

A

white precipitate

dissolves when excess NaOH is added

32
Q

Calcium in NaOH

A

White precipitate

33
Q

Copper ions in NaOH

A

Blue precipitate

34
Q

Iron (II) ions in NaOH

A

Green precipitate

35
Q

Iron (III) ions in NaOH

A

Brown precipitate

36
Q

Ammonium ions (NH4) in NaOH

A

Pungent smelling gas produced

Gas turns red litmus paper blue

37
Q

Ammonia chemical test

HCl

A

when hydrogen chloride gas is held near the ammonia, from concentrated HCl, it forms a white smoke of aluminium chloride

38
Q

Type of reaction from calcium carbonate to calcium oxide

A

thermal decomposition

39
Q

Why does Br2 have a lower boiling point than ICl

A

Bromine has London forces acting between the molecules, whereas ICl has London forces and permanent dipole-dipole interactions

Permanent dipole dipole interactions are stronger than induced dipole-dipole interactions

40
Q

Why are halogens non polar

A

Both atoms have the same electronegativity values

No permanent dipole- so molecule is non polar

41
Q

Test to distinguish between AgBr and AgI

A

Concentrated ammonia solution

AgBr will dissolve to produce a colourless solution

AgI is insoluble- yellow solid remains