Group 2 Flashcards by Joyston De Souza

Features of atomic radius in Group 2 elements (2)

Atomic radius increases down the group.
Because the atoms have more
shells of electrons making the atom bigger.

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Features of melting points in group 2 atoms (4)

Melting points decrease down the group.
The metallic bonding weakens as the atomic size increases.
The distance between the positive ions and delocalized electrons increases.
Therefore the electrostatic
attractive forces between the positive ions and the delocalized electrons Weaken

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Features of 1st ionisation energy (2)

The outermost electrons are held more weakly because they are successively further from the nucleus in additional shells.
In addition, the outer shell electrons become more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons.

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Reactivity

Increases as you go down the group

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Magnesium reactions with oxygen and what are the observations

Observations: Mg burns with a white flame and MgO appears as a white powder

2Mg + O2 –> 2MgO

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Mg and MgO reaction with HCl

Mg + 2HCl–>MgCl2 + H2
MgO + 2HCL –>MgCl2 + H2O

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Magneisum reaction with steam and warm water

Steam:
Mg(s)+ H2O(g)–>MgO(s)+ H2 (g)

Warm water:
Mg + 2H2O–>Mg(OH)2 + H2

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The other group 2 metals will react with cold water with
increasing vigour down the group to form hydroxides. and what are the observations

Ca + 2H2O (l)Ca(OH)2 (aq)+H2 (g)
Sr+2 H2O (l) Sr(OH)2 (aq) + H2(g)
Ba+ 2H2O (l) Ba(OH)2(aq) + H2(g)

One would observe: fizzing, (more vigorous down group) the metal dissolving, (faster down group) the solution heating up (more down group) with calcium a white precipitate appearing
(less precipitate forms down group with
other metals)

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Why can titanium not be extracted with carbon

Titanium cannot be extracted with carbon because titanium carbide (TiC) it is formed rather than titanium

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Why is titanium expensive

Titanium is expensive because:
1. The expensive cost of the magnesium
2. This is a batch process which makes it expensive because the
process is slower (having to fill up and empty reactors takes
time) and requires more labour and the energy is lost when the
reactor is cooled down after stopping
3. The process is also expensive due to the argon, and the need to
remove moisture (because TiCl4
is susceptible to hydrolysis).
4. High temperatures required in both steps

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Titanium reactions

TiO2 + 2 Cl2 + 2 C –>TiCl4 + 2 CO

TiCl4 + 2Mg –>Ti + 2 MgCl2

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Flue gas desulfurisation

SO2 + CaO  CaSO3

Neutralisation reaction
The calcium sulfite which is formed can be used to make calcium sulfate for plasterboard.

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Solubility of Hydroxides

Group II hydroxides become more soluble down the group. All Group II hydroxides when not soluble appear as white precipitates

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What is the simplest ionic equation for formation of Mg(OH)2(s)

Mg2+(aq) + 2OH-(aq) –> Mg(OH)2 (s).

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Features of Calcium hydroxide

Calcium hydroxide is classed as partially soluble in water and will appear as a white precipitate It is used in agriculture to neutralise
acidic soils.
Can be used to test for carbon dioxide (Limewater)
- Ca(OH)2 + CO2 –> CaCO3 +H2O

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Use of Mg(OH)2 and reaction with HCl

Neutralises excess acid in the stomach to treat constipation

Mg(OH)2 + 2HCl –> MgCl2 + 2H2O
It is safe to use because it is so weakly alkaline. It is
preferable to using calcium carbonate as it will not
produce carbon dioxide gas

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Solubility of sulfates

Group II sulfates become less soluble down the group. BaSO4
is the least soluble.

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An equation for the formation of the precipitate can be written as a full equation or simplest ionic equation.

Full equation :
SrCl2(aq) + Na2SO4 (aq)  2NaCl (aq) + SrSO4 (s)

Ionic equation:
Sr2+(aq) + SO4^2-(aq)  SrSO4
(s)

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Use of Barium sulfate

The barium absorbs the x-rays and so the gut shows up on the x-ray image.

Even though barium compounds are toxic, it is safe to use here because barium sulfate’s low solubility means it is not absorbed into the blood.

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Barium reaction with H2SO4

Ba + H2SO4 –> BaSO4 + H2

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Testing for presence of a sulfate ion and give the simplest ionic equation

BaCl2 solution acidified with hydrochloric acid is used as a reagent to test for sulfate ions.

If acidified barium chloride is added to a solution that contains sulfate ions a
white precipitate of barium sulfate forms

Simplest ionic equation
Ba2+ (aq) + SO4^2-(aq) –> BaSO4
(s)

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What is the trend in atomic radius down Group 2, and why? (4)

Atomic radius increases.
The number of principal energy levels increases.
There is more shielding.
Weaker attraction between the nucleus and outer electrons.

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What is the trend in first ionisation energy down Group 2, and why? (3)

First ionisation energy decreases.
The number of principal energy levels increases, causing more shielding.
Weaker attraction between the nucleus and the outer electron.

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What is the trend in melting point down Group 2, and why? (3)

Study These Flashcards

Melting point decreases.
The size of the atom/ion increases.
Weaker electrostatic attraction between positive ions and delocalised electrons.

What happens when Group 2 elements react with water? (2)

The metal atom loses electrons and becomes a metal 2+ ion

Why does reactivity increase down Group 2? (3)

- Atoms become larger. - The distance between the nucleus and outer electron increases. - There is more shielding

How does the reactivity of Group 2 elements with water change down the group? (2)

- Reactivity increases - The reaction becomes more vigorous

What is the reaction of magnesium with liquid water? (2)

- Mg (s) + 2H₂O (l) → Mg(OH)₂ (s) + H₂ (g) - Very slow reaction

What is the reaction of magnesium with steam? (2)

- Mg (s) + H₂O (g) → MgO (s) + H₂ (g) - Very fast reaction

What is the reaction of calcium with water? (2)

Ca (s) + 2H₂O (l) → Ca(OH)₂ (s) + H₂ (g)

What is the reaction of strontium with water? (2)

Sr (s) + 2H₂O (l) → Sr(OH)₂ (aq) + H₂ (g)

What is the reaction of barium with water? (2)

Ba (s) + 2H₂O (l) → Ba(OH)₂ (aq) + H₂ (g

What is the least soluble group 2 hydroxide? (1)

Mg(OH)2 (basically insoluble)

What is the most soluble group 2 hydroxide? (1)

Ba(OH)2

What happens to the solubility of group II hydroxides in water down the group? (1)

Solubility in water increases down the group

What happens to the pH of group II hydroxides as a base down the group? (1)

The pH increases down the group because there are more hydroxide ions in the solution.

What is observed when sodium hydroxide is added to magnesium chloride? (2)

- White ppt - Because magnesium hydroxide is insoluble in water

Write the ionic equation for the reaction between magnesium chloride and sodium hydroxide. (2)

Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s)

What is observed when sodium hydroxide is added to barium chloride? (1)

No precipitate is seen because barium hydroxide is soluble in water

What is the test for hydroxide ions? (2)

- Magnesium chloride solution is added to a solution containing hydroxide ions - A white precipitate of Mg(OH)₂ is formed

What is the test for magnesium ions? (2)

- Sodium hydroxide solution is added to a solution containing magnesium ions - A white precipitate of Mg(OH)₂ is formed

What is the most soluble group 2 sulfate? (1)

MgSO4

What is the least soluble group 2 sulfate? (1)

BaSO4 (insoluble)

What happens to the solubility of group II sulfates in water down the group? (1)

Decreases down the group

How do you test for sulfate ions? (2)

- Add acidified barium chloride solution to a solution containing sulfate ions - A white precipitate of BaSO₄ is formed

How do you test for barium ions? (2)

- Add sulfuric acid to a solution containing barium ions. - A white precipitate of BaSO₄ is formed

Why must an unknown solution be acidified with HCl or HNO₃ before testing for barium ions? (2)

Acidification removes carbonate ions that could interfere with the test

Why is H₂SO₄ not used to acidify the solution before testing for barium ions? (2)

- H₂SO₄ contains sulfate ions - Which would form a white precipitate and interfere with the test

What are the two reactions for the extraction of titanium by magnesium? (2)

- TiO₂(s) + 2Cl₂(g) + 2C(s) → TiCl₄(g) + 2CO(g) - TiCl₄(g) + 2Mg(l) → Ti(s) + 2MgCl₂(l)

What is the condition needed for the extraction of titanium by magnesium? (1)

Very high temperatures (600-900°C)

What is the use of Ca(OH)₂ in agriculture? (1)

Ca(OH)₂ is used to neutralise acidic soils

What is the ionic equation for Ca(OH)₂ neutralising acids? (2)

H⁺ + OH⁻ → H₂O

What is Mg(OH)₂ used for in medicine? (2)

- Known as 'milk of magnesia' - Used to neutralise stomach acid (HCl) and treat indigestion.

What are the uses of CaO and CaCO₃ in flue gas desulfurisation? (3)

- CaO and CaCO₃ are used to neutralise SO2 - Which can cause acid rain - Thus preventing its emission

Why can CaCO₃ not be used to treat indigestion? (1)

It produces CO₂ gas

What is the equation for CaO neutralising SO₂? (1)

CaO + SO₂ → CaSO₃

What is BaSO₄ used for in diagnostic medicine? (2)

- Used as a barium meal before x-rays or CT scans - To identify damaged or diseased areas of the digestive tract

Why is BaSO₄ safe to use despite barium being toxic? (2)

BaSO₄ is safe because it is insolublem

Group 2 Flashcards

(58 cards)