Module 2: Group 2 (Alkaline Earth Metals) Flashcards

1
Q

What is the trend in atomic radius down group 2 & why?

A
  • Increases
  • Atomic number increases & shielding increases.
  • Extra electron shells are added increasing distance between nucleus & outer electrons.
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2
Q

What is the trend in first ionisation energy down group 2 & why?

A
  • Decreases
  • Each element has an extra electron shell compared to the one above (greater atomic radius).
  • Electrons lost more easily due to increased shielding.
  • Electrostatic attraction between nucleus & outer electrons decreases.
  • The increasing positive charge of nucleus (due to extra protons) is overridden by the effect of the extra shells.
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3
Q

What is the trend in reactivity down group 2 & why?

A
  • Increases
  • React to lose electrons & form positive ions.
  • Energy needed to form positive ions falls due to decrease in ionisation energy.
  • Leads to lower Ea & faster reactions.
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4
Q

What is the trend in melting point down group 2 & why?

A
  • Decreases
  • Greater shielding & atomic radius offsetting greater nuclear charge.
  • Metal ions increase in size so less energy required to break metallic bonds.
  • Weaker electrostatic forces of attraction between positive ions & delocalised electrons.
  • Drop with Mg as sudden change in crystal structure.
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5
Q

What is the type of bonding found between group 2 atoms?

A

Metallic bonding

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6
Q

What is the trend in reactivity of group 2 metals with water?

A
  • Increase.
  • React with increasing vigour.
  • Ionisation energy decreases.
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7
Q

What is produced when group 2 metals react with water?

A

Metal hydroxide & hydrogen

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8
Q

What is the general reaction for a group 2 metal with water?

A

M (s) + 2H2O (l) –> M(OH)2 (aq) + H2 (g)

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9
Q

What is the reaction of Mg with cold water?

A

Mg (s) + 2H2O (l) –> Mg(OH)2 (aq) + H2 (g)

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10
Q

How does Mg react with cold water?

A

Very slowly

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11
Q

How does Mg react with steam

A

Rapidly

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12
Q

What is the reaction of Mg with steam?

A

Mg (s) + H2O (g) –> MgO (s) + H2 (g)

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13
Q

What is the reaction of MgO with cold water?

A

MgO (s) + H2O (l) –> Mg(OH)2 (aq)

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14
Q

What is the reaction of Ca with cold water?

A

Ca (s) + H2O (l) –> Ca(OH)2 (aq) + H2 (g)

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15
Q

What is the reaction of Mg with dilute HCl?

A

Mg (s) + HCl (aq) –> MgCl2 (aq) + H2 (g)

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16
Q

What is the reaction of Ca with dilute H2SO4?

A

Ca (s) + H2SO4 (aq) –> CaSO4 (s) + H2O (l)

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17
Q

What is observed when Mg is reacted with dilute HCl?

A
  • Exothermic reaction
  • Vigorous bubbling
  • Effervescence
  • Warm test tube
  • White precipitate
18
Q

What is observed when Mg is reacted with dilute H2SO4?

A
  • Exothermic reaction
  • Hydrogen gas given off
19
Q

What is observed when Ca is reacted with dilute HCl?

A
  • Exothermic reaction
  • Effervescence
  • Warm test tube
  • Vigorous reaction
20
Q

What is observed when Ca is reacted with dilute H2SO4?

A
  • Exothermic reaction
  • White precipitate
  • Limited reaction
21
Q

Why is their a limited reaction when Ca reacts with H2SO4 compared to Mg?

A

CaSO4 is less soluble compared to MgSO4.

22
Q

What is the trend in solubility of hydroxides?

A

Solubility increases down the group.

23
Q

What is the least soluble hydroxide?

A

Mg(OH)2

24
Q

What is the most soluble hydroxide?

A

Ba(OH)2

25
Q

What is the trend in solubility of sulfates?

A

Solubility decreases down the group.

26
Q

What is the solubility of Mg(OH)2 in water?

A

Sparingly soluble

27
Q

What is the solubility of BaSO4 in water?

A

Insoluble in water

28
Q

What is the use of BaSo4?

A
  • Used in medicine as barium meals.
  • Aid in diagnosing problems with oesophagus, stomach or intestines.
  • Insoluble, so can’t be absorbed into the bloodstream.
29
Q

What is the test for sulfate ions?

A
  • Add dilute HCl.
  • Add solution of BaCl2
  • If sulfate is present, white precipate is produced.
  • Ba2+ (aq) + SO4^2- (aq) –> BaSO4 (s)
30
Q

Why is dilute HCl added when testing for sulfates?

A

To remove any carbonate ions present that may disrupt results & form a white precipitate of BaCO3.

31
Q

What is the process of using Mg to extract Ti from its ore?

A
  • Titanium (IV) oxide (TiO2) is converted to titanium (IV) chloride (TiCl4) by heating it with carbon in a stream of chlorine gas.
  • TiCl4 is then purified by fractional distillation.
  • Then reduced by magnesium in a furnace at
32
Q

What are the equations for the extraction of Ti using Mg?

A
  • TiO2 (s) + 2Cl2 (g) + 2C (s) –> TiCl4 (g) + 2CO (g)
  • TiCl4 (g) + 2Mg (l) –> Ti (s) + 2MgCl2 (l)
33
Q

What are the conditions for titanium extraction & why?

A
  • Reaction heated under high temperature & inert conditions.
  • Mg may react with air & produce inaccurate results
34
Q

Why is titanium more expensive to produce?

A
  • Titanium requires a series of reactions to extract it from its ore.
  • Made in batches which is time consuming & expensive.
35
Q

What are the properties & use of Mg(OH)2?

A
  • Sparingly soluble.
  • Sold as ‘Milk of Magnesia’ in water solution.
  • Used in indigestion tablets as an antacid to neutralise excess stomach acid.
36
Q

What are the properties & use of Ca(OH)2?

A
  • Sparingly soluble.
  • Solution used as lime-water.
  • Used in agriculture to neutralise acidic soils.
37
Q

What is wet scrubbing?

A

The process of removing acidic sulfur dioxide from flue gases by reacting them with an alkali.

38
Q

Name two alkalis that can be used in wet scrubbing?

A
  • Calcium oxide (Lime, CaO).
  • Calcium carbonate (Limestone, CaCO3).
39
Q

What is the process of removing SO2 from flue gases (west scrubbing)?

A
  • A slurry is made by mixing CaO or CaCO3 with water.
  • This is sprayed onto the flue gases.
  • SO2 reacts with the alkaline slurry to produce a solid, waste product of CaSO3.
40
Q

What are the equations for the removal of SO2 from flue gases (wet scrubbing)?

A
  • CaO (s) + 2H2O (l) + SO2 (g) –> CaSO3 (s) + 2H2O (l).
  • CaCO3 (s) + 2H2O (l) + SO2 (g) –> CaSO3 (s) + 2H2O (l) + CO2 (g).