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UACE Chemistry > Group II Elements > Flashcards

Group II Elements Flashcards

1
Q

True or false
Group II elements are less electropositive than group I elements

A

True

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2
Q

True or False
Group II elements are more reactive than group I elements

A

False

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3
Q

True or false
Group II elements are good reducing agents

A

True
(Weaker than Group I though)

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4
Q

Why do group II elements have higher melting and boiling points than group I elements?

A
  • Group II metals contribute 2 electrons per atom to their charge cloud. Their atoms carry a bigger charge and have a smaller ionic radii
  • Therefore they form stronger electrostatic attraction between the positively charged metal ions and delocalized electrons resulting into stronger metallic bonds that require more heat energy to break
  • Group I metals contribute 1 electron per atom to their charge cloud. Their atoms carry a smaller charge and have a bigger ionic radii
  • The electrostatic attraction between the group I cations and delocalized electrons is less resulting into weaker metallic bonds that require less heat energy to break resulting into lower melting points
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5
Q

True or false
Group II compounds are less ionic than corresponding group I elements

A

True

  • Group II cations form smaller cations with a bigger positive charge (+2) thus they have a higher charge density and polarizing power
  • Group II cations exert a greater polarizing power on anions than group I cations do
    (makes it more covalent-like than ionic)
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6
Q

Why are group II salts less soluble than group I salts?

A

Both the lattice energies of group II salts and hydration energies of group II cations are much higher than those of corresponding group I salts and group I cations respectively

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7
Q

Why does Beryllium show a significant difference in its chemical properties from the rest of the alkaline earth metals?

A

Very small ionic radius thus high charge density and polarizing power. Therefore it readily distorts the electron cloud of negatively charged ions forming covalent compounds

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8
Q

How do group II metals react with air?

A
  • Burn in oxygen forming white solid metal oxides
  • Magnesium and calcium also react with nitrogen in air and form nitrides
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9
Q

How do group II metals react with acids?

A
  • All react with dilute mineral acids forming a salt and hydrogen gas.
  • Beryllium is rendered inactive by nitric acid
  • Vigor of the reaction increases down the group but for sulphuric acid it reduces after magnesium due to formation of insoluble sulphates.
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10
Q

How do beryllium and magnesium react with concentrated sulphuric acid?

A

Form a sulphate, sulphur dioxide and water

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11
Q

True or false
Beryllium is rendered inactive by nitric acid

A

True

This is due to formation of a protective oxide, beryllium oxide that causes the reaction to stop

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12
Q

How do group II metals react with water?

A
  • Beryllium does not react with water
  • Magnesium slowly reacts with cold or hot water but vigorously reacts with steam forming magnesium oxide (white solid) and hydrogen gas.
  • Calcium, Strontium and Barium react with cold water forming a metal hydroxide and hydrogen gas.
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13
Q

How do group II metals react with alkalis?

A
  • Beryllium reacts with hot concentrated sodium hydroxide (because of its greater polarizing power) forming a soluble complex of tetrahydroxoberyllate ions and hydrogen gas.
  • Other elements do not react with alkalis
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14
Q

How do group II metals react with halogens?

A
  • Hot group II metals react with halogens forming white solid metal dihalides
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15
Q

How do group II metals react with hydrogen gas?

A
  • Heated group II metals react with hydrogen gas forming solid metal hydrides
    (Hydrides of Be and Mg are covalent while those of Ca, Sr, Ba are ionic)
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16
Q

How are oxides of group II elements prepared?

A
  • Heating metal carbonates or nitrates
  • In the case of MgO; passing steam over heated Mg
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17
Q

True or false
All group II oxides except BeO are basic

A

True
BeO is amphoteric

But all group II oxides (including Be) react with acids forming salt and water only

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18
Q

What is the result of reacting Beryllium oxide with an alkali?

A

Soluble complex of tetrahydroxoberyllate ion

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19
Q

Why can’t BeO, MgO and CaO form peroxides but Sr and Ba can?

A

BeO, MgO and CaO cations are too small to form stable lattices while Sr and Ba cations are big enough to form stable lattices

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20
Q

How are hydroxides of group II metals prepared?

A
  • Action of water on their metal oxides
  • Action of aqueous sodium hydroxide on soluble salts of the metals
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21
Q

True or false
All group II hydroxides are basic

A

False
Beryllium hydroxide is amphoteric, the rest are basic

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22
Q

What is the result of reacting group II metal hydroxides and acids?

A

A salt and water only

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23
Q

True or false
Beryllium hydroxide reacts with alkalis

A

True
Forms a soluble complex of tetrahydroxoberyllate ions

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24
Q

What is the trend of solubility of group II hydroxides?

A

Solubility increases down the group

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25
Q

Explain why the solubility of group II hydroxides increases down the group

A

Down the group, both lattice energy and hydration energy decrease in magnitude but lattice energy decreases more rapidly than hydration energy

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26
Q

Explain why the solubility of group II hydroxides increases down the group

A

Down the group, both lattice energy and hydration energy decrease in magnitude but lattice energy decreases more rapidly than hydration energy

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27
Q

How are group II sulphates prepared

A

Action of aqueous sodium sulphate on aqueous solutions of metal salts

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28
Q

Describe and explain the trend in solubility of group II sulphates
Solubility of sulphates decreases down the group

A

Both lattice energy and hydration energy of group II sulphates decrease but hydration energy decreases more rapidly than lattice energy

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29
Q

How are group II carbonates prepared?

A

Precipitation by adding aqueous sodium carbonate to an aqueous solution of a group II salt

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30
Q

Describe and explain the trend in solubility of group II carbonates

A

All are insoluble in water

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31
Q

What is the trend of thermostability of group II carbonates?

A

Increases down the group

Explanation:
- The ionic radius of group II ions increases from Be2+ to Ba2+, but the ionic charge remains constant
- The ionic character of the carbonates increases down from beryllium carbonate to barium carbonate due to reduction in polarizing power
- Due to increase in ionic character of the carbonates, their decomposition temperature increases down the group

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32
Q

What is the trend of hydrolysis of group II salts?

A
  • As the cationic radius increases from beryllium to barium, the charge density and polarizing power of the cations reduces as well
  • As the polarizing power decreases down the group, the degree of hydrolysis of group II also decrease
  • Be2+ ion with the highest polarizing power has its salts hydrolyzed in water forming acidic solutions
  • The high polarizing power of the beryllium ion results into formation of the strong Be–O bond that weakens the O–H bond in the complex
  • The solvent water molecules remove a proton from the complex, forming hydronium ions in the solution becomes acidic
  • A few magnesium and calcium salts are hydrolyzed in water forming slightly acidic solutions
  • Sr and Ba salts are not hydrolyzed in water
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33
Q

Define a complex

A

A complex is a compound or ion consisting of a Central metal ion or atom bonded to negatively charged ions or neutral molecules with lone pairs of electrons through coordinate bonding

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34
Q

What factors favor complex ion formation?

A
  1. small, highly charged cations
  2. Presence of empty orbitals on the Central metal ion or atom
  3. Lone pair of electrons on the ligands
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35
Q

Why does the ability to form complexes decrease down the group in group II?

A

This is because as ionic radius increases down the group, both the charge density and polarizing power decrease, and the ability of the cations to attract lone pairs of electrons from ligands reduces

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36
Q

What is a ligand?

A

A negatively charged ion or neutral molecule, with at least one lone pair of electrons, which it can donate to empty orbitals of a metal cation or atom

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37
Q

Define diagonal relationship

A

This is the trend in which elements in adjacent groups and periods of the periodic table at right angles to each other show similar chemical properties.

38
Q

Give examples of pairs of elements that exhibit diagonal relationship

A

Lithium and magnesium
Beryllium and aluminum
Boron and silicon

39
Q

Why does beryllium show anomalous behavior from the rest of the group II elements?

A
  1. Beryllium has high ionization energy compared to other group members
  2. Beryllium ion has a very small ionic radius compared to the rest of the group II cations. This results into high charge density and polarizing power that favors covalent bonding and high lattice energy resulting into low, solubility of beryllium compounds in water.
  3. Beryllium is much more electronegative compared to the rest of the group II members in this favors covalent bonding.
40
Q

Why do beryllium and aluminum show diagonal relationship?

A
  1. Both have similar electronegativity
  2. Both have similar polarizing power
  3. Both have high and similar ionization energy
41
Q

In which ways do beryllium and aluminum show diagonal relationship?

A
  1. Both metals are rendered passive by nitric acid (due to the formation of a protective layer)
  2. Both metals react with hot, concentrated, sodium hydroxide, liberating, hydrogen gas
  3. The oxide and hydroxide of both the beryllium and aluminum are amphoteric
  4. Their chlorides are polymeric, and when anhydrous readily dissolve in organic solvents, and are readily hydrolyzed by water, liberating, hydrogen chloride gas
  5. Both beryllium carbide and aluminum carbide give methane when reacted with water
  6. Similar complexes of beryllium and aluminum show similar stabilities
42
Q

In which properties do lithium and magnesium show diagonal relationship?

A
  1. On combustion, both lithium and magnesium form normal oxides
  2. Both magnesium and lithium and heated combine directly with nitrogen forming metal nitrides
  3. The carbonates, fluorides and phosphates of both lithium and magnesium are insoluble in water
  4. Both lithium and magnesium react with carbon forming ionic carbides
  5. Their hydroxides, nitrates, and carbonates are readily decomposed on heating
43
Q

How does magnesium react with air?

A
  • At ordinary temperature magnesium is not attacked by dry air.
  • It burns with a bright white flame on strong heating, forming a white ash consisting of magnesium oxide and magnesium nitride.
  • If to the products, a little water is added, and the mixture warmed ammonia gas is involved.
44
Q

How does magnesium react with dilute acids?

A

With dilute hydrochloric, sulphuric acid and nitric acid, magnesium readily liberate, hydrogen gas

45
Q

How does magnesium react with concentrated acids?

A

With concentrated sulphuric acid, magnesium liberates sulphur dioxide gas

46
Q

How does magnesium react with non-metals?

A

Hot magnesium vigorously reacts with several non-metals, including chlorine, sulphur, nitrogen, and phosphorus, forming a variety of compounds

47
Q

How can one prepare magnesium oxide?

A
  • Strong heating of magnesium carbonate
  • Strong heating of magnesium hydroxide
  • Strong heating of magnesium nitrate
48
Q

How is magnesium hydroxide prepared?

A

By precipitation, by adding aqueous sodium hydroxide to an aqueous solution of any soluble magnesium salt

49
Q

True or false
Magnesium hydroxide is only slightly soluble in water

A

True

50
Q

True or false
Magnesium hydroxide is acidic and does not react with acids

A

False
Magnesium hydroxide is basic, and readily reacts with acids forming a salt and water

51
Q

How is magnesium carbonate prepared?

A

By adding aqueous sodium hydrogen carbonate to aqueous magnesium sulphate

52
Q

Why is sodium hydrogen carbonate solution preferred to sodium carbonate solution in the preparation of magnesium carbonate?

A

Sodium hydrogen carbonate solution is much less hydrolyzed producing much fewer hydroxide ions than sodium carbonate when in solution

53
Q

How is anhydrous magnesium chloride prepared?

A

Heating magnesium in a stream of dry chlorine gas, or hydrogen chloride gas

54
Q

How are magnesium chloride crystals prepared?

A

Reacting excess magnesium metal, magnesium oxide, magnesium hydroxide, or magnesium carbonate with dilute hydrochloric acid, and filtering off the excess solid to obtain a solution of magnesium chloride, which is concentrated by evaporation and left a cool, forming crystals of the salt

55
Q

Why can’t anhydrous magnesium chloride be obtained directly by heating hydrated magnesium chloride?

A

The hydrated salt undergoes hydrolysis on heating to a basic compound

56
Q

How are magnesium sulphate crystals prepared?

A

Reacting, either excess magnesium metal, magnesium oxide, magnesium hydroxide, or magnesium carbonate with dilute sulphuric acid, and filtering of the excess solid to obtain a solution of magnesium sulphate which is concentrated by evaporation and left to cool to form crystals of the salt

57
Q

How does calcium react with air?

A
  • When exposed to air at room, temperature, calcium forms in succession, its oxide, hydroxide, and carbonate
  • When heated in air it burns with a brick red flame, forming a white solid, consisting of a mixture of calcium oxide and calcium nitride
  • Ammonia, gas is liberated when to the mixture warm water is added
58
Q

How does calcium react with water?

A

It readily reacts, liberating, hydrogen gas, and forming calcium hydroxide, which is only slightly soluble in water. Therefore, a white suspension is seen in the water.

59
Q

How does calcium react with hydrogen gas?

A

When heated in a stream of dry hydrogen gas it produces a colorless salt-like solid called calcium hydride

Calcium hydride, liberates, hydrogen gas when reacted with cold water

60
Q

How is calcium oxide/quicklime prepared?

A

Strongly heating calcium carbonate to about 1300K

61
Q

How does calcium oxide react with cold water?

A

If cold water is added to the oxide it produces a hissing sound, and the material swells cracks and crumbles into a white powder in an exothermic reaction, forming calcium hydroxide/slaked slime

62
Q

How is calcium hydroxide prepared?

A

Action of excess water on calcium oxide

63
Q

True or false calcium hydroxide is only slightly soluble in water

A

True

Forms a colorless solution of calcium hydroxide solution

64
Q

What is the action of carbon dioxide gas on calcium hydroxide solution (lime water)?

A
  • limewater turns milky due to the formation of insoluble calcium carbonate
  • However, if excess carbon dioxide is used the insoluble calcium carbonate, dissolves, forming a colourless solution consisting of calcium hydrogen carbonate, which is which is soluble in water
65
Q

How does calcium hydroxide react with acids?

A

Calcium hydroxide is strongly basic and reacts with acids forming a salt and water

66
Q

How is calcium carbonate prepared?

A
  • Calcium carbonate is prepared as a white precipitate by mixing hot solutions of calcium chloride and sodium carbonate
  • The precipitate is filtered, washed with hot distilled water and dried in a steam oven
67
Q

True or false
Calcium carbonate is soluble in water

A

False
It is practically insoluble

68
Q

What happens to calcium carbonate on heating?

A

Decomposes on heating, forming calcium oxide, and carbon dioxide (reversible reaction)

69
Q

How does calcium carbonate react with acids?

A
  • With dilute nitric acid or dilute hydrochloric acid, Calcium carbonate reacts readily liberating carbon dioxide gas.
  • With dilute sulphuric acid, the reaction stops after a short period of time due to formation of a coating of insoluble calcium sulphate on the calcium carbonate, preventing it from further acid attack
70
Q

How is calcium sulphate prepared?

A

Prepared as a white precipitate, by mixing moderately concentrated hot solutions of calcium chloride and sodium sulphate

71
Q

True or false
Calcium sulphate is soluble in water

A

False
Calcium sulphate is only sparingly soluble in water

72
Q

True or false
Calcium sulphate is soluble in water

A

False
Calcium sulphate is only sparingly soluble in water

73
Q

How can calcium chloride be prepared?

A
  • Reacting excess calcium carbonate with dilute hydrochloric acid and then filtering off the excess solid to obtain a solution of calcium chloride which is concentrated by evaporation and left to cool to form crystals of the salt
  • Anhydrous calcium chloride can be obtained by heating the hydrated salt to dryness
74
Q

What is the result of calcium carbide reacting with cold water?

A

It rapidly reacts with cold water forming calcium hydroxide and ethyne gas

75
Q

What is the result of magnesium ions reacting with sodium hydroxide solution?

A

White precipitate insoluble in excess alkali

76
Q

What is the result of magnesium ions reacting with ammonia solution?

A

White precipitate insoluble in excess ammonia

  • however this precipitate does not form in presence of ammonia chloride which suppresses ionization of ammonia solution leading to insufficient hydroxide ions to reach the solubility product of magnesium hydroxide
77
Q

What is the result of magnesium ions reacting with aqueous sodium carbonate/ aqueous ammonium carbonate?

A

White precipitate formed

78
Q

What is the result of magnesium ions reacting with sodium phosphate/ disodium hydrogen phosphate?

A
  • To test the solution, solid ammonium chloride is added followed by little sodium phosphate or disodium hydrogen phosphate solution
  • A white precipitate forms slowly, insoluble in ammonia but soluble in acids
79
Q

What is the result of calcium ions reacting with sodium hydroxide solution?

A

White precipitate insoluble in excess alkali

80
Q

What is the result of calcium ions reacting with ammonia solution?

A

No observable change in dilute conditions/ slight white precipitate

81
Q

What is the result of calcium ions reacting with aqueous sodium carbonate?

A

White precipitate formed

82
Q

What is the result of calcium ions reacting with dilute sulphuric acid?

A

White precipitate forms slowly

83
Q

What is the result of calcium ions reacting with ammonium oxaloate solution?

A

White precipitate insoluble in hot ethanoic acid but soluble in mineral acids

84
Q

What is the result of calcium ions reacting with sodium phosphate/ sodium hydrogen phosphate solution solution?

A

White precipitate forms

85
Q

What is the result of barium ions reacting with sodium hydroxide solution?

A

White precipitate insoluble in excess alkali

86
Q

What is the result of barium ions reacting with ammonia solution?

A

No observable change ( if all solutions are prepared in distilled water)

87
Q

What is the result of barium ions reacting with aqueous sodium carbonate?

A

White precipitate formed

88
Q

What is the result of barium ions reacting with dilute sulphuric acid?

A

A heavy white precipitate forms instantly

89
Q

What is the result of barium ions reacting with ammonium oxaloate solution?

A

White precipitate soluble in hot ethanoic acid in dilute mineral acids but not in sulphuric acid

90
Q

What is the result of barium ions reacting with sodium phosphate/ sodium hydrogen phosphate solution solution?

A

White precipitate forms

91
Q

What is the result of barium ions reacting with potass chromate solution?

A

A yellow precipitate formed, soluble in mineral acids but not dilute sulphuric acid forming an orange solution but insoluble in aqueous sodium hydroxide

UACE Chemistry (20 decks)

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