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AQA A Level Inorganic Chemistry > 2. Group 2, alkaline earth metals > Flashcards

2. Group 2, alkaline earth metals Flashcards

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1
Q

What are the elements in group 2 called?

A

The alkaline earth metals

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2
Q

What is atomic radius?

A

The distance from the centre of the nucleus to the outer electrons

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3
Q

What happens to atomic radii down group II?

A

It increases

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4
Q

Why does atomic radius increase down group II?

A
  • more shells as you move down the group
  • so increased distance from nucleus
  • so atomic radius ↑
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5
Q

What is the first ionisation energy?

A

The enthalpy change when 1 mole of gaseous atoms forms one mole of positive gaseous atoms (by losing 1 mole of electrons)

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6
Q

What happens to first ionisation energy down group II?

A

Decreases

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7
Q

Why does first ionisation energy decrease down group II?

A
  • more shells down group
  • outer electrons so ↑ distance from nucleus
  • so increased shielding
  • so weaker attraction for outer electrons
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8
Q

What is melting point?

A

The point at which sufficient bonds are broken/loosened within the substance so that the solid and liquid phase are in equilibrium

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9
Q

What happens to the melting point down group II?

A

Decreases

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10
Q

Why does melting point decrease down group II?

A
  • Metals held by metallic bonds

* Atomic radii ↑ down group but same number of delocalised electrons = less attraction between metal ions and electrons

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11
Q

What is the irregularity in the trend that melting point decreases down group II?

A

Mg

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12
Q

Why is Mg an irregularity in the trend that melting point decreases down group II?

A

It has a different crystal structure from the other elements, which is less packed and therefore easier to separate

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13
Q

Which group II compounds react with water?

A

All of them

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14
Q

What do group II compounds react with water to produce?

A

The metal hydroxide and hydrogen

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15
Q

What is the rate of reaction when Mg reacts with water?

A

Very slow

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16
Q

What is the equation for the reaction of Mg with water?

A

Mg₍ₛ₎ + H₂O₍ₗ₎ → Mg(OH)₂₍ₐᵩ₎ + H₂₍𝓰₎

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17
Q

What happens when Mg is heated in steam?

A

It will burn to form an oxide

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18
Q

What is the equation for the reaction of Mg with steam?

A

Mg₍ₛ₎ + H₂O₍𝓰₎ → MgO₍ₛ₎ + H₂₍𝓰₎

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19
Q

For group II elements, from calcium to barium, how do they react with cold water down the group?

A

React with increasing vigour down the group

20
Q

Why do group II elements, from calcium to barium, react more vigorously with water down the group?

A
  • more likely to lose electrons
  • larger atom/more shells
  • greater distance from nucleus to outer electrons
  • ↑ shielding
  • easier to lose outer electrons
21
Q

What is solubility?

A

The maximum amount of solute that will dissolve in a given volume of solvent

(i.e. how easily it dissolves)

22
Q

How soluble is something when it is ‘sparingly soluble’?

A

Not very soluble

23
Q

Why is Mg(OH)₂ considered to be sparingly soluble?

A

A very small amount of it dissolves, giving a suspension of magnesium hydroxide in water (milk of magnesia)

24
Q

How is milk of magnesia formed?

A

Magnesium hydroxide is dissolved, giving a suspension in water

25
Q

How soluble is Mg(OH)₂?

A

Sparingly

26
Q

How soluble is Ca(OH)₂?

A

Quite - dissolves almost fully in water

27
Q

What happens when calcium hydroxide is added to water?

A

It dissolves almost fully to form lime water

28
Q

What happens when barium/strontium hydroxide are added to water?

A

They both dissolve to produce strongly alkaline solutions - OH- fully dissociates

29
Q

What happens when elements below barium in group II are added to water?

A

They dissolve easily and form clear solutions

30
Q

What happens to the solubility of the hydroxides down group II?

A

It increases

31
Q

What happens to the solubility of the sulphates down group II?

A

It decreases

32
Q

What is barium sulphate used to test for?

A

The presence of sulphate ions

33
Q

Why is barium sulphate used to test for sulphate ions?

A

Solubility of the sulphates decreases down group Ii

34
Q

What does barium chloride form in the presence of sulphate ions?

A

White precipitate

35
Q

How is the sulphate test carried out?

A
  1. Add HCl to solution being tested

2. Add aqueous barium chloride - if sulphate ions present, then white precipitate of barium sulphate forms

36
Q

Why is HCl added in the sulphate test?

A

Removes any other ions that could give a precipitate with barium chloride e.g. carbonate ions

37
Q

When HCl is added in the sulphate test, what is formed as a result?

A

CO₂ and H₂O

38
Q

What is the solubility of BaCl₂ like in water?

A

Very soluble

39
Q

Equation for sulphate test, with magnesium sulphate?

A

BaCl₂ + MgSO₄ → BaSO₄ + MgCl₂

40
Q

What is Mg(OH)₂ used for?

A
  • laxative - relieve constipation - ↑ water in intestines

* antacid - relieve indigestion and heart burn

41
Q

What is Ca(OH)₂ used for?

A

↑ PH level in the soil into the optimal range (6-7) - for plant growth and uptake of nutrients (also known as hydrated lime)

42
Q

What is BaSO₄ used for?

A
  • used in medical imaging of the gastrointestinal tract as it is opaque to X-rays
  • BaSO₄ solution ingested by patient, covers oesophagus, stomach and intestines
43
Q

Why is BaSO₄ used for barium meals?

A

Other Ba compounds are toxic, and other group II metal compounds are soluble

44
Q

What is CaO or CaCO₃ used for?

A

To remove SO₂ produced in burning fuels

45
Q

What is Mg used for?

A

In the extraction of Ti from TiCl₄:

TiO₂ converted to TiCl₄ by heating with carbon and chlorine. TiCl₄ then reduced by Mg

46
Q

Equation for reduction of TiCl₄ by Mg?

A

TiCl₄ + 2Mg → Ti + 2MgCl₂

AQA A Level Inorganic Chemistry (6 decks)

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