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Chemistry AS Level CIE > Chapter 11 Group 2 > Flashcards

Chapter 11 Group 2 Flashcards

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1
Q

group 2 elements reaction with oxygen

A
  • Be=reluctant to burn, white flame
  • Mg= burns easily, bright white flame
  • Ca= difficult to ignite, red flames
  • Sr= difficult to ignite, red flame
  • Ba= difficult to ignite, green flame
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2
Q

group 2 elements reaction with water

A
  • Be= no reaction
  • Mg= vigorous reaction with steam, no reaction with water
  • Ca= reacts moderately, hydroxide formed
  • Sr= reacts rapidly, hydroxide formed
  • Ba= reacts vigorously, hydroxide formed
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3
Q

group 2 elements reaction with dilute HCL

A
  • Be= reacts rapidly
  • Mg= reacts vigorously
  • Ca=reacts vigorously
  • Sr=reacts vigorously
  • Ba=reacts vigorously
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4
Q

group 2 elements reaction with dilute H2SO4

A

-Be=reacts vigorously
-Mg=reacts vigorously
-Ca=reaction slowed down by the formation of a sparingly soluble sulfate layer that covers the metal, stopping hydrogen bubbles from rising
-Sr and Ba= reaction is quickly stopped by the formation of an insoluble sulfate layer on the metal surface
\

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5
Q

The reaction of all metals with oxygen follows the following general equation:

A

2M(s) + O2(g) → 2MO(s)
-Where M is any metal in Group 2

Remember than Sr and Ba also form MO2

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6
Q

The reaction of all metals with water follows the following general equation:

A

M(s) + 2H2O(l) → M(OH)2(s) + H2(g)

Except for, Be which does not react with water

-Where M is any metal in Group 2

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7
Q

The reaction of all metals with dilute HCl follows the following general equation:

A

M(s) + 2HCl(aq) → MCl2(aq) + H2(g

-Where M is any metal in Group 2)

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8
Q

The reaction of all metals with dilute H2SO4 follows the following general equation:

A

M(s) + H2SO4(aq) → MSO4(aq) + H2(g)

Remember that SrSO4 and BaSO4 are insoluble
-Where M is any metal in Group 2

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9
Q

Reactions of group 2 oxides

A
  • All Group 2 oxides are basic, except for BeO which is amphoteric (it can act both as an acid and base)
  • Group 2 oxides react water to form alkaline solutions which get more alkaline going down the group
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10
Q

Group 2 oxide reactions with water table: BeO, MgO, CaO, SrO, BaO

A
  • BeO = no observation
  • MgO =MgO is only slightly soluble in water, therefore a weakly alkaline solution is formed (pH 10)
  • CaO = Vigorous reaction releases a lot of energy which cause some of the water to boil off as CaO solid lump seems to expand and crack open (pH 11)
  • SrO = no observation
  • BaO= no observation
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11
Q

oxide + water =

A

hydroxide

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12
Q

calcium hydroxide other name

A

lime water

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13
Q

same property for al group 2 oxides according to colour

A

s are white solids which form colourless solutions of metal chlorides when they react with a dilute acid
-The reaction of a metal oxide with a dilute acid is a neutralisation reaction

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14
Q

solubility for all group 2 sulfates down a group

A

Group 2 sulfates become less and less soluble

  • These insoluble sulfates form at the surface of the oxides which means that the solid oxide beneath it can’t react with the acid
  • This can be prevented by using the oxide in powder form and stirring in which case signification neutralisation can take place
  • Remember that:
  • –oxide + dilute hydrochloric acid → salt + water

—oxide + dilute sulfuric acid → sulfate + water

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15
Q

Reactions of group 2 hydroxides properties of colour and solubility

A
  • The Group 2 metal hydroxides form colourless solutions of metal chlorides when they react with a dilute acid
  • The sulfates decrease in solubility going down the group (barium sulfate is an insoluble white precipitate)
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16
Q

Group 2 hydroxide reactions with dilute acids =

A

hydroxide + dilute acid → salt + water

hydroxide + dilute sulfuric acid → sulfate + water

17
Q

Reactions of group 2 carbonates according to solubility

A
  • All Group 2 carbonates (except for BeCO3) are insoluble in water
  • All Group 2 carbonates will form soluble chloride salts, water and carbon dioxide gas when reacted with dilute hydrochloric acid
  • The carbonates of Ca, Sr and Ba form as an insoluble sulfate layer on their solid carbonates which stops any further reaction after the initial bubbling (effervescence) of carbon dioxide gas is seen
18
Q

Group 2 carbonate reactions with dilute acids=

A

carbonate + dilute hydrochloric acid → salt + water + carbon dioxide

carbonate + dilute sulfuric acid → sulfate + water + carbon dioxide

19
Q

Thermal decomposition

A

is the breakdown of a compound into two or more different substances using heat

20
Q

Thermal decomposition of carbonates

A

-The Group 2 carbonates break down (decompose) when they are heated to form the metal oxide and give off carbon dioxide gas
-The general equation for the decomposition of Group 2 carbonates is:
XCO3(s) —> heat —> XO(s) + CO2(g)
X=group 2 element

-Going down the group, more heat is needed to break down the carbonates

21
Q

Thermal decomposition of nitrates

A

The Group 2 nitrates break decomposed when they are heated to form the metal oxide, oxygen gas and nitrogen dioxide gas (which is a brown toxic gas)
Since the formed nitrogen dioxide gas is toxic, the decomposition of nitrates is often carried out in a fume cupboard

22
Q

The general equation for the decomposition of Group 2 nitrates is:

A

2x(NO3)2(s) —> heat —> 2XO(s) + 4NO2(g) + O2(g)
X = group 2 element

  • Going down the group, more heat is needed to break down the nitrates
  • –The smaller positive ions at the top of Group II will polarise the nitrate ions more than the larger ions at the bottom of the group
  • –The more polarised they are, the more likely they are to thermally decompose
23
Q

Group 2: Chemical trends

A
  • All elements in Group 2 (also called alkali earth metals) have the two electrons in their outermost principal quantum shell
  • All Group 2 metals can form ionic compounds in which they donate these two outermost electrons (so they act as reducing agents) to become an ion with +2 charge (so they themselves become oxidised)
  • Going down the group, the metals become more reactive
24
Q

The first ionisation energy is the energy needed

A

to remove the first outer electron of an atom

25
Q

The second ionisation energy is the energy needed to

A

to remove the second outer electron of an atom

26
Q

the elements become more reactive going down

A
  • it becomes easier to remove the outer two electrons of the metals
  • Though the nuclear charge on the nucleus increases going down the group (because there are more protons), factors such as an increased shielding effect and a larger distance between the outermost electrons and nucleus outweigh the attraction of the higher nuclear charge

-gets easier for the atoms to lose two electrons and become 2+ ions

27
Q

reactivity shown by looking at reactions of the Group 2 metals:

A
  • With dilute hydrochloric acid: bubbles of hydrogen gas are given off much faster indicating that the reactions become more vigorous
  • With oxygen hydrochloric acid: the metals get more reactive with oxygen down the group (Ba is so reactive, that it must be stored in oil to prevent it from reacting with oxygen in air)
28
Q

Group 2: Physical trends

A
  • Going down the group, the elements become larger as the outer two electrons occupy a new principal quantum shell which is further away from the nucleus
  • The melting point of the elements decreases going down the group as the outer electrons get further away from the nucleus
  • This means that the attraction between the nucleus and the bonding electrons decreases causing a decrease in melting point
  • As you go down the group, the density of the alkali earth metals increases
29
Q

Group 2 hydroxides

A
  • Going down the group, the solutions formed from the reaction of Group 2 oxides with water become more alkaline
  • When the oxides are dissolved in water, the following ionic reaction takes place:

O2- (aq) + H2O(l) → 2OH– (aq)

  • The higher the concentration of OH– ions formed, the more alkaline the solution
  • The alkalinity of the formed solution can therefore be explained by the solubility of the Group 2 hydroxides
30
Q

The hydroxides dissolve in water as follows:

A

X(OH)2 (aq) → X(aq) + 2OH– (aq)

Where X is the Group 2 element

31
Q

Going down the group

A

Going down the group, the solubility of the hydroxides increases which means that the solutions formed from the reactions of the Group 2 metal oxides and water become more alkaline going down the group

32
Q

Group 2 sulfates

A

-The solubility of the Group 2 sulfates decreasing going down the group

Chemistry AS Level CIE (21 decks)

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