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Chemsitry > Group 2+7 > Flashcards

Group 2+7 Flashcards

1
Q

Why does a flame test work

A

When metal compound is heated electrons in the metal ion are excited to a higher energy level
As electrons return to normal energy level the energy is emitted as visible light
The colour of light emitted is due to the energy gap

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2
Q

How does solubility of hydroxides change down the group

A

Hydroxides increase in solubility down the group

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3
Q

How do sulfates change in solubility down the group

A

Sulfates decrease in solubility down the group

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4
Q

Formula of a metal sulfate

A

XSO4

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5
Q

Formula of group 2 hydroxide

A

X(OH)2

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6
Q

Flame test colour of lithium

A

Crimson

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7
Q

Flame test colour of sodium

A

Yellow

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8
Q

Flame test colour of potassium

A

Lilac

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9
Q

Flame test colour of beryllium

A

No change

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10
Q

Flame test colour of magnesium

A

No change

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11
Q

Flame test colour of calcium

A

Brick red

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12
Q

Flame test colour of strontium

A

Red

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13
Q

Flame test colour of barium

A

Green

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14
Q

Why does thermal stability of group 2 carbonate change

A

As you go down group 2 ionic radius increases
Therefore charge density increases
Less able to polarise carbonate ion
Therefore more energy required to break C-O bond

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15
Q

What is thermal decomposition

A

The breaking down of a substance using heat energy
Is exothermic

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16
Q

Properties of group 7 elements

A

Non-metal
Reactive
Not found natively (as pure elements)
Usually found in compounds with metals eg halide salts

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17
Q

How does the reactivity of group 7 elements change down the group

A

Less reactive down the group

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18
Q

Why does reactivity change down group 7

A

Halogens form 1- ion by gaining outer shell electron
Further out outer shell makes it harder to gain an electron

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19
Q

Why is ionic radii greater than atomic radii group 7

A

Because an electron has been gained and now more electrons than protons
Hence attraction between nucleus and each electron decreases

20
Q

Change in melting/boiling of group 7 and why

A

Increase down the group

Only London forces so bigger molecule creates stronger forces so more energy required to break

21
Q

Why do all halogens have similar chemical properties

A

All react to gain one outer shell electron

22
Q

Are group 7 elements oxidising or reducing agents

A

Tend to gain electrons in reaction so are likely to be oxidising agents and be reduced

23
Q

When will group 7 element not have negative oxidation state

A

When combined with oxygen as oxygen is more electronegative

24
Q

How does oxidising ability change down group 7

A

Decreases
Ability to gain electrons decreases down group as number of shells increases so outer electron further from nucleus and more shielding

25
Q

Why are group 7 poorly soluble with water

A

Unable to form hydrogen bonds with water so can’t release enough energy to overcome hydrogen bonds between water molecules

26
Q

Why are group 7 soluble in cyclohexane

A

Both have London forces as strongest intermolecular bonds
Energy released by forming London forces between halogen and solvent releases enough energy to break London forces between halogen and solvent

27
Q

Physical state at room temp for Cl, Br and I and why

A

Cl- gas
Br- liquid
I- solid

Increase in number of electrons so increase in strength of London forces

28
Q

Why has hydrogen flouride got higher boiling point than expected

A

Has intermolecular hydrogen binding and therefore intermolecular forces require more energy to break

29
Q

What happens in redox reaction of group 7 and 1/2 metal

A

Electrons transferred from metal to halogen to form metal halide

30
Q

Appearance of metal halide

A

Generally white solid

31
Q

What happens in reaction of chlorine and water

A

Produces a mixture of two acids

H2O + Cl2 becomes HCl and HOCl

32
Q

Why does redox chlorine and water form two acids

A

Cl is oxidised to form HOCl and reduced to form HCl

33
Q

Reaction of chlorine and COLD alkali

A

Forms sodium chlorate (I)

Cl2 + 2NaOH becomes NaCL + NaClO + H2O

34
Q

Reaction of chlorine and HOT alkali

A

Forms sodium chlorate (V)

3Cl2 + 6NaOH becomes 5NaCl + NaClO3 + 3H2O

35
Q

What is hydrogen halide displacement

A

A more reactive halogen will take the place of a less reactive halogen

36
Q

Reactivity of halogens from most reactive to least

A

Fluorine
Chlorine
Bromine
Iodine

37
Q

What does bromine dissolve in

A

An organic solvent

38
Q

Precipitate colour reaction of silver nitrate and chlorine

A

White

39
Q

Precipitate colour reaction of silver nitrate and bromine

A

Cream

40
Q

Precipitate colour reaction of silver nitrate and iodine

A

Yellow

41
Q

How to differentiate between yellow and cream precipitate

A

Silver bromine (cream) will not dissolve in aqueous ammonia but will dissolve in conc ammonia
Silver iodide (yellow) is insoluble in both aqueous and conc ammonia

Therefore add concentrated ammonia

42
Q

Basic ionic formula for silver nitrate and halogen

A

Ag+(aq) + X-(aq) becomes AgX (s)

43
Q

Result of adding aqueous barium chloride followed by dilute hydrochloride acid

A

White pot insoluble in hydrochloric acid

SO42- ions present

44
Q

Result of adding dilute acid to compound

A

Effervescence giving colourless gas and gas turning water guilty = CO3 2- ions present

Pungent colourless gas on warming that decolourises potassium manganate = SO3 2- ions present

45
Q

Result of adding aqueous sodium hydroxide and heat

A

Gas that turns damp red litmus paper blue means NH4+ ions present

46
Q

Result of adding aqueous sodium hydroxide

A

White precipitate insoluble in excess reagent means insoluble metal hydroxide- group 2 metal ions likely

47
Q

Result of warm solid with aqueous sodium hydroxide and aluminium/zinc powder

A

Gas that turns damp red litmus paper blue means NO3- ions present reduced to NH3

Chemsitry (15 decks)

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