group 2

Question 1

why are group 2 known as alkaline earth metals

Answer 1

• they react with water to form alkalis (metal hydroxides) and hydrogen.

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Question 2

write an equation for the first ionisation energy of magnesium .

Answer 2

Mg (g) —> Mg+ (g) + e-

Question 3

what happens to the first ionisation energy as you go down group 2? why?

Answer 3

• decreases as number of filled electron shells increases down group —> increased shielding, increased atomic radius —> weaker force between outer electron and nucleus —> less energy needed to remove electron

Question 4

how does reactivity with water change as you go down group 2?

Answer 4

• increases (Mg lease —> Ba most)
• outer electrons get further away from nucleus , reducing nuclear attraction
• electron shielding increases, further reduces attraction between positive nucleus + outer electrons
• outer two electrons more easily lost to form +2 ions .

Question 5

write an equation for the reaction of Barium and water.

Answer 5

• Ba (s) + 2H2O (l) —> Ba(OH)2 (aq) + H2 (g)
• metal + water —> metal hydroxide + hydrogen

Question 6

write an equation for the reaction of magnesium and steam .

Answer 6

• Mg (S) + H2O (g) —> MgO (s) + H2 (g)

Question 7

What’s the trend in hydroxide solubility down group 2?

Answer 7

• Increases down the group
• Mg(OH)2 is almost insoluble
• Ba(OH)2 creates strong alkaline solution.

Question 8

what’s the trend in sulphate solubility down group 2?

Answer 8

• decreases down group
• MgSO4 is soluble
• BaSO4 is insoluble

Question 9

What’s the equation when calcium oxide neutralises hydrochloric acid to form a salt and water ? (bases which neutralise acids)

Answer 9

• CaO + 2HCl —> CaCl2 + H2O

Question 10

what’s the trend in melting point down group 2 ? why?

Answer 10

• decreases down group
• because sea of delocalised electrons is further from the positive charge of the nucleus —> weaker metallic bonds/ forces of attraction which take less energy to weaken.

Question 11

what’s the trend in atomic radius down group 2?

Answer 11

• increases as more occupied electron shells down the group .

Question 12

write the equation for the extraction of Titanium using Magnesium.

Answer 12

• TiO2 + 2Cl2 + C —> TiCl4 + CO2
• TiCl4 (l) + 2Mg (s) —> 2MgCl2 (s) + Ti (s)

Question 13

what are flue gases ?

Answer 13

• gases produced by power stations which are harmful to environment

Question 14

how can CaO or CaCO3 be used to remove flue gases? write equations

Answer 14

• CaCO3 (s) + SO2 (g) —> CaSO3 (s) + CO2 (g)
• CaO (s) + SO2 (g) —> CaSO3 (s)

Question 15

what is Ca(OH)2 used for ? write an equation related to one of its uses.

Answer 15

• used to neutralise soil
• Ca(OH)2 (aq) + 2HCl (aq) —> 2H2O (l) + CaCl2 (aq)

Question 16

what is Mg(OH)2 used for ?

Answer 16

• milk of magnesia - antacid to treat indisgestion, heartburn , wind etc

Question 17

what’s a use for BaSO4? why is it safe ?

Answer 17

• in barium metals to outline gut in x-rays Ba2+ is toxic but is fine as barium sulphate is insoluble .

Question 18

how can BaCl2 be used to test for sulfate ions?

Answer 18

add your sample with HCl first to acidify the solution, then add BaCl2 . white precipitate will form if sulfate ions are present

• Ba^2+ + SO4^2- —> BaSO4

Question 19

how are group 2 compounds neutralise acids?

Answer 19

1) as antacids = magnesium hydroxide and calcium carbonate used in indigestion tablets to neutralise excess stomach acid.

2) calcium hydroxide (slaked lime) used in farming to neutralise acidic soils