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chemistry > topic 4A > Flashcards

topic 4A Flashcards

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1
Q

atomic radius down group 2

A

increases because the atoms have more shells of electrons

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2
Q

melting points down group 2

A

decreases becuase metallic bonding weakens as atomic size increases. Distance between positive ions and delocalised electrons increases so electrostatic force of attraction between them weakens

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3
Q

what happens to 1st ionisation energy down the group

A

outermost electrons are held more weakly as they are further from the nucleus.
outer shell electrons become more shielded
so it decreases

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4
Q

reactivity of group 2 metals down a group

A

increases as the atomic radii increases hence there is more shielding. Nuclear attraction decreases so it’s easier to remove outer electrons

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5
Q

reactions with oxygen

A
  • they burn in oxygen
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6
Q

Magnesium?

A

burns with white flame

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7
Q

Barium reactivity?

A

most reactive

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8
Q

Berylium?

A

no reaction

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9
Q

Calcium?

A

burns with a red flame producing calcium oxide

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10
Q

barium?

A

burns with green flame

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11
Q

react with chlorine?

A

group 2 metals will react with chlorine

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12
Q

reactions with water - Mg

A

reacts in steam to produce magnesium oxide and hydrogen
also reacts with warm water giving a different magnesium hydroxide product (very slow reaction)

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13
Q

reactions with water - other group 2 metals

A

react with cold water with increasing effervescence down the group to form hydroxides

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14
Q

observations

A

fizzing
metal dissolving
solution heating up

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15
Q

observation with calcium

A

white precipitate forming

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16
Q

solubility of hydroxides

A

become more soluble down the group.
when not soluble they appear as white precipitate

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17
Q

is magnesium hydroxide soluble?

A

insoluble
MgOH is used in medicine to neutralise excess acid in stomach and treat constipation
safe to use because it is weakly alkaline

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18
Q

is calcium hydroxide soluble

what is it used for

A

reasonably soluble
used in agriculture to neutralise acidic soils
lime water is an aqueous solution of CaOH which is used as a test for CO2

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19
Q

is barium hydroxide soluble?

A

would easily dissolve
hydroxide ions present would make solution strongly alkaline

20
Q

solubility of sulfates

A

group 2 sulfates become less soluble down the group
BaSO4 is least soluble

21
Q

what would happen if barium reacted with sulfuric acid

A

would react slowly as the insoluble barium sulfate produced would cover the surface of the metal and act as a barrier to further attack

22
Q

thermal decomposition

A

use of heat to break down a reactant into more than 1 product

23
Q

what happens to group 2 carbonates when heated

A

they decompose to produce group 2 oxides and carbon dioxide gas

24
Q

ease of thermal decomposition down group 2?

A

decreases
become more thermally stable
cations get bigger - less polarising effect - CO bond weakens - less easily break down

25
Q

investigating ease of thermal decomposition

A

heat known mass of carbonate in a boiling tube and pass the gas through limewater. Time for the first permanent cloudiness to appear in the lime-water. Repeat for different carbonates using same moles and same volume of lw

26
Q

thermal decomposition of group 2 nitrates

A

they decompose to produce group 2 oxides, oxygen and nitrogen dioxide gas

27
Q

word equation for thermal decomposition of group 2 nitrates

A

metal nitrate -> metal oxide + nitrogen dioxide + oxygen

28
Q

change in thermal stability explanation

A

Magnesium nitrate decomposes the easiest because the Mg2+ ion is smallest and has the greater charge density. Causes more polarisation of the nitrate anion and weakens N-O bond

29
Q

Group 1 nitrates decomposition

A

metal nitrate –> nitrate salt + oxygen

30
Q

method for flame test

A
  • use nichrome wire
  • dip in concentrated HCl and heat under Bunsen flame
  • If sample is not powdered, grind it up
  • Dip wire in solid and put in Bunsen flame and observe flame colour
31
Q

flame colour for Lithium

A

carmine red

32
Q

flame colour for sodium

A

orange

33
Q

flame colour for potassium

A

lilac

34
Q

flame colour for rubidium

A

purple

35
Q

flame colour for caesium

A

violet

36
Q

flame colour for magnesium

A

no colour

37
Q

flame colour for calcium

A

brick red

38
Q

flame colour for strontium

A

crimson

39
Q

flame colour for barium

A

green

40
Q

flame colour for berylium

A

no colour

41
Q

flame colour for copper

A

blue/green

42
Q

explanation for occurence of flame colours

A

heat causes electron to move to higher energy level
electron is unstable at higher energy level so drops back down.
as it drops from high energy to low energy, energy is emitted in the form of visible light with wavelength of observed light

43
Q

problems with flame tests

A
  • many compounds contain small amounts of sodium impurities
  • colours are subjective as different levels of colour vision in people
  • ‘brick’ red depends on the brick
  • lilac/lavender/ mauve/ purple are similar
44
Q

reaction of group 2 elements with dilute acids

A
  • they form a salt and hydrogen gas
45
Q

reaction of group 2 hydroxides with dilute acids

A
  • they form a salt

chemistry (28 decks)

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