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Chemistry > Topic 4: inorganic chemistry and the periodic table > Flashcards

Topic 4: inorganic chemistry and the periodic table Flashcards

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1
Q

State and explain the trend in MP going down group 2 metals

A

MP decreases. themetallic bond weaks as the atomic size increases. electrostatic attraction between the positive ions and the delocalised electrons decreases therefore less energy needed to break the bonds.

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2
Q

State and explain the trend in 1st ionisation energy going down group 2

A

1st ionisation energy decreases. atoms are getting larger and therefore the outermost electrons are further from the nucleus and more shielded, decreasing the attraction between the nucleus and the electrons therefore less energy needed to remove the outer electrons.

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3
Q

state the trend in reactivity going down group 2 metals

A

reactivity increases down the group as its easier to lose the electrons

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4
Q

magnesium + oxygen

A

2Mg + O2 -> 2MgO
MgO is a white solid with a high mp due to its ionic bonding
Mg burns with a bright white flame

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5
Q

when using magnesium ribbon, why do you need to clean it before use

A

magnesium reacts slowly with oxygen without a flame. therefore the magnesium ribbon will have a thin layer of magnesium oxide on it.
if testing for reaction rates with Mg and acid, the Mg and MgO would react at different rates, giving false results
MgO + HCl-> MgCl2 + H2O

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6
Q

magnesium + steam

A

Mg + H2O(g) -> MgO + H2

bright white flame

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7
Q

magnesium + warm water

A

Mg + 2H2O -> Mg(OH)2 + H2

much slower reaction than with steam and no flame

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8
Q

group 2 metals + cold water products

A

froms the hydroxide (aq) + H2 (g)

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9
Q

observations when group 2 metals react with hydroxides and trends in the reaction going down the group

A

fizzing (morevigorous down group)
the metal dissolves(faster down the group)
solution heats up (more down the group)

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10
Q

calcium + cold water observation

A

a white precipitate appears (less precipitate forms down the group)

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11
Q

group 2 oxides are ionic/basic?

A

basic as the oxide ions accept protons to become hydroxide ions (when reacting with water)

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12
Q

groups 2 oxides + water products

A

just the hydroxide (s)
reaction with Mg gives pH9, with calcium gives pH12. This is because magnesium is only slightly soluble in water so fewer free OH- produced

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13
Q

group 2 oxides + acid

A

-> salt (aq) + water

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14
Q

groups 2 hydroxides + acids

A

-> salt (aq) + water
Eg
Mg(OH)2 (aq) + 2HNO3 (aq) -> Mg(NO3)2 (aq) + 2H2O(l)

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15
Q

solubility of group 2 hydroxides

A

become more soluble down the group

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16
Q

all group 2 hydroxides when not soluble appear as __

A

white precipitates

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17
Q

how is magnesium hydroxide used in medicine

A

in suspension as milk of magnesia to neutralise excess acid in the stomach and to treat constipation.
it is safe to use because it is so weakly alkaline. more preferable to use than calcium carbonate as it will not produce CO2

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18
Q

calcium hydroxide use in agriculture

A

neutralise acidic soils

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19
Q

how can an aqueous solution of calcium hydroxide be used to test for CO2

A

aqueous solution of calcium hydroxide is limewater.
limewater turns cloudy as the white calcium carbonate is produced.
Ca(OH)2 (aq) + CO2 -> CaCO3 (s) + H2O (l)

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20
Q

barium hydroxide + water ionic equation

A

Ba(OH)2 (s) + aq -> Ba2+ (aq) + 2OH- (aq)

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21
Q

solubility of group 2 sulfates

A

group 2 sulfates become less soluble going down the group

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22
Q

why does barium metal react slowly with sulfuric acid

A

insoluble barium sulfate produced will cover the surface of the metal and act as a barrier to further attack
same effect does not happen with other acids like HCL or HNO3 as they form soluble group 2 salts

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23
Q

thermal decomposition of group 2 carbonates

A

group 2 carbonates become more thermally stable going down the group. as cations get bigger they have less of a polarising effect and distort the carbonate less therefore the C-O bond is weakened and more energy needed to break it.

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24
Q

what is the group 1 carbonate that is the exception and will decompose

A

lithium carbonate

lithium ion is small enough ot have a polarising effect on the carbonate ion. it has a big enough charge density

25
Q

is it easier or harder to thermally decompose group 2 carbonates going down the group

A

going down the group it gets harderto thermally decompose them

26
Q

define thermal decomposition

A

the use of heat to break down a compound into more than one product

27
Q

MgCO3 (s) ->

A

MgO (s) + CO2 (g)

28
Q

how would you investigate thermal stability of group 2 carbonates

A

heata known mass of carbonate in a side arm boiling tube
pass the gass produced through limewater
time for limewater to go cloudy

29
Q

thermal decomposition of group 2 nitrates (V)

A

becomes harder to decompose going down the group
they decompose to produce group 2 oxides and nitrogen dioxide gas
(lithium nitrate decomposes the same as group 2 nitrates)

30
Q

observation when decomposing group 2 nitrates

A 
brown gas (NO2) 
whitenitrate solid is seen to melt to a colourless solution and then re solidify
31
Q

equation for thermal decomposition of magnesium nitrate

A

2Mg(NO3)2 -> 2MgO + 4NO2 +O2

32
Q

how do group 1 nitrates, with the exception of lithium nitrate decompose

A

decompose to give a nitrate (III) salt and ocygen

2NaNO3 -> 2NaNO2 + O2

33
Q

flame test

A

nichrome wire
clean by dipping inot conc HCL
dip into solid and then into blue flame
observe colour change

34
Q

explain flame tests

A

an excited electron is promoted to a higher energy level by the heat from the flame
when the electron drops to a lower energy level, energy is released in the from of visible light

35
Q

why is there no flame colour with magnesium

A

energy emitted of a wavelength outside visible spectrum

36
Q

appearance of halogens at room temp

A

fluorine- very pale yellow gas, highly reactive
chlorine- greenish, reactive gas, poisonous in high conc
bromine- red liquid, it gives off dense brown/orange poisonous fumes
iodine- dark grey solid, sublimes to purple gas

37
Q

trend in MP and BP of halogens down the group

A

increases down the group

molecules are larger, more electrons, larger London forces, more energy needed to overcome the intermolecular forces

38
Q

trend in electronegativity of halogens

A

going down the group, the EN decreases

atomic radii increases, nucleus is less able to attract the bonding pair of electrons

39
Q

define electronegativity

A

electronegativity is the relative tendency of an atom in a molecule to attract electrons in a covalent bond to itself

40
Q

oxidising strength of halogens down the group

A

oxidising strength decreases down the group- harder to accept electrons

41
Q

potassium bromide + chlorine ionic eq

A

Cl2(aq) + 2Br- (aq) -> 2Cl- (aq) + Br2 (aq)

42
Q

potassium iodide + chlorine ionic eq

A

Cl2 (aq) + 2I- (aq) -> 2Cl- (aq) + I2 (aq)

43
Q

potassium iodide + bromine ionic eq

A

Br2 (aq) + 2I- (aq) -> 2Br- (aq) + I2 (aq)

44
Q

halogen + metal reactions- what is oxidsed

A

the metals are oxidised

Br2 (l) + 2Na(s) -> 2NaBr (s)

45
Q

reaction between chlorine/ bromine with iron (II)

A

iron (II) is oxidised to (III)

Cl2 (g) +2Fe2+ (aq) -> 2Cl- (aq) + 2Fe3+ (aq)

46
Q

reaction between iodine and iron (II)

A

iodine is not a strong oxidising agent to oxidise iron (II) to iron (III). the reaction is reversed
2I- (aq) + 2Fe3+ (aq) -> I2 (aq) + 2Fe2+ (aq)

47
Q

define disproportionation

A

a reaction where an element is simultaneously oxidised and reduced

48
Q

chlorine + water

A

disproportionation

Cl2 (g) + h2o(l) -> HClO (aq) +HCl (aq)

49
Q

observations with chlorine + water disproportionation reaction

A

adding universal indicator will first turn it red due to acidity of both reaction products. then turns colourless as HCLO bleaches the colour

50
Q

useof chlorine

A

usedin water treatment. used to treat drinking water and water in swimming pools

51
Q

reaction of aqueous halogens with cold dilute NaOH solution

A

Cl2 9aq) +2NaOH (aq) ->NaCl (aq) + NaClO (aq) +H2O (l)

mixture of NaCl and NaClO is used as bleach and to disinfect/kill bacteria

52
Q

reaction of halogens with hot dilute NaOH solution

A

disproportionation occurs but the halogen is oxidised

3Cl2 (aq) +6NaOH(aq) -> 5NaCl (aq) +NaClO3 (aq) +3H2O (l)

53
Q

explain trend in reducing power of HALIDES going down the group

A

increasing reducing power down the group
they have a greater tendency to donate electrons as ions get bigger so attraction between nucleus ans the outer electrons decreases

54
Q

sulfuric acid+ fluoride/chloride

A

no redox reaction occurs as the sulfuric acid is not strong enough to oxidise the halides.
acid base reactions occur
NaF (s) + H2SO4 (l) -> NaHSO4 (s) +HF(g)
HF is white steamy fumes

55
Q

sulfuric acid + bromide

A

after the intial acid bas step, bromide reduces the sulfur in H2SO4 from 6+ to 4+ in SO2
acid basestep: NaBr(s) + H2SO4(l) -> NaHSO4 (s) +HBr (g)
redox step: 2HBr + H2SO4 -> Br2 (g) +SO2(g) +2H2o (l)
in first step sulfuric acid acts as an acid but in 2nd step acts as an oxidising agent as itgets reduced

56
Q

observations of sulfuric acid + bromide

A

in acid base step: white steamy fumes of HBr

in redox step: red fumes of Br2 (g) and a colourless, acidic gas SO2 (g)

57
Q

iodide + sulfuric acid (4 steps)

A

NaI(s) + H2SO4 (l) -> NaHSO4 (s) +HI
2HI + H2SO4 -> I2 (s) + SO2(g) +2H20 (l)
6HI + H2SO4 -> 3I2 + S (s) + 4H2O(l)
8HI + H2SO4 -> 4I2 (s) + H2S (g) + 4H2O (l)

58
Q

oxidation numbers of sulfur when reacting with iodide

A

+6 in H2SO4 to
+4 in SO2 to
0 in S to
-2 in H2S

59
Q

observations with iodide and sulfuric acid

A 
HI gives white steamy fumes 
black solid and purple fumes of I2
colourless acidic gas of SO2
yellow solid of sulfur 
bad egg smell gas H2S

Chemistry (8 decks)

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