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Chemistry A Level > Group 2 - the alkaline metals > Flashcards

Group 2 - the alkaline metals Flashcards

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1
Q

How reactive are they?

A

Fairly reactive, less reactive than group 1

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2
Q

Atomic radius trend down group 2

A
  • Increases down group 2 due to more electron shielding so electron becomes further away from nucleus
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3
Q

Ionisation energy trend down group 2

A
  • 1st ionisation energy decreases down, as atomic radius and shielding increases so electron is easier to remove as less attraction between electron and nucleus
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4
Q

Melting point trend down group 2

A
  • Decrease down group
  • Because delocalised electrons further away from nucelus
  • Further down the group the weaker the attraction between between nucleus and delocalised electrons
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5
Q

How does magnesium react with water and give the equation?

A
  • Very slowly
  • Magnesium hydroxide formed
  • Mg + 2H2O(l) –> Mg(OH)2 + H2
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6
Q

How does magnesium react with steam and give the equation?

A
  • Reacts readily with steam
  • Magnesium oxide formed
  • Mg + H20(g) –> MgO + H2O
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7
Q

Why is magensium oxide formed rather than magnesium hydroxide with steam?

A
  • As hydroxide not stable at higher temperatures
  • It thermally decomposes to give magnesium oxide and water
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8
Q

How do calcium, strontium and barium react with water?

A
  • They produce metal hydroxides and hydrogen
  • The reactivity of the reaction increases as group descends
  • Calcium releases bubbles of hydrogen and a white ppt
  • Strontium more reactive than calcium, less white ppt formed, barium even less white ppt formed
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9
Q

Give equations of Ba, Sr, and Ca with water

A
  • Ca + 2H2O —> Ca(OH)2 + H2
  • Sr + 2H2O —> Sr(OH)2 + H2
  • Ba + 2H2O —> Ba(OH)2 + H2
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10
Q

Solubility of group 2 hydroxides in water

A
  • Become more soluble down the group
    • Magnesium hydroxide sparingly soluble as solution slightly alkaline indicating some hydroxide ions are dissolved in the water
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11
Q

Observations of Ca2+ with sodium hydroxide

A

White ppt of calcium hydroxide

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12
Q

Observations of Mg2+ with sodium hydroxide

A

Thick white ppt of magnesium hydroxide

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13
Q

Observations of Sr2+ with sodium hydroxide

A

Thin white ppt of strontium hydroxide

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14
Q

Observations of Ba2+ sodium hydroxide

A

Very thin white ppt of barium hydroxide

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15
Q

Solubility of group 2 sulfates in water

A
  • Decrease in solubility down the group
  • Calcium sulfate said to be sparingly soluble and barium sulfate insoluble
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16
Q

Observation of Mg2+ with sodium sulfate

A

No ppt

17
Q

Observation of Ca2+ with sodium sulfate

A

Thin white ppt

18
Q

Obsevation of Sr2+ with sodium sulfate

A

White ppt

19
Q

Observation of Ba2+ with sodium sulfate

A

Thick white ppt

20
Q

The test of barium salts for a sulfate

A
  1. Add 1cm3 of dilute HCl
  2. Add 1cm3 aqueous barium chloride solution
  3. If thick white ppt formed then sulfate ions present
21
Q

Simplest ionic equation for test for sulfate ions with barium salts

A

Ba2+(aq) + SO42- (aq) –> BaSO4(s)

22
Q

What is magnesium used for?

A
  • Extraction of titanium
  • Titanium can be used for aerospace, marine and motor vehicles due to high corrosion resistance
23
Q

Equation of magnesium extracting titanium

A

TiCl4 + 2Mg —> Ti + 2MgCl2

24
Q

Magnesium hydroxide use

A
  • ‘Milk of magnesia’ given to alleviate constipation and as an antacid
  • Solution only slightly alkaline so does not irritate oesophagus
25
Q

Calcium hydroxide use

A
  • ‘Slaked slime’ neutralises acidic soil, reducing the acidity so plants can grow without nasty side effects
  • Improves availabitlity of nutrients like phosphorus and improves texture of soil so smaller seedlings can break through soil surface
26
Q

Cacium oxide use

A
  • Neutralises sulfure dioxide to prevent formation of acid rain.
  • Calcium carbonate can also be used
27
Q

Barium sulfate use

A
  • ‘Barium meal’
  • Barium good at absorbing x-rays and can outline the gut
  • Barium ions toxic but technique is harmless as barium sulfate insoluble and cannot be absorbed into blood
28
Q

Electronegativity down group 2

A
  • Decreases down the group
  • More inner energy levels of electron shielding the attractive power of the nucleus which combined with increase in atomic radius leads to decrease in electronegativity despite increased nuclear charge
29
Q

Why is water never added to burning Mg

A

Hydrogen could explode

30
Q

Any group 2 metal with water equation

A

Mg (s) + 2H2O —> Mg(OH)2 + H2

31
Q

Any group 2 metal with oxygen

A

2Ca + O2 —> 2CaO

32
Q

Any group 2 metal with acid

A

2Sr + 2HCl —> SrCl2 + H2

33
Q

Any group 2 metal with TiCl4

A

2Mg + TiCl4 —> 2MgCl2 + Ti

34
Q

Ionisation energy graph down group 2

A

Chemistry A Level (25 decks)

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