3.2.2 - GROUP 2 , AKALINE EARTH METALS

Question 1

What happens to the atomic radius down group 2

Answer 1

Increases, due to added electron shells

Question 2

What happens to the ionisation energy as you go down Group 2 and why

Answer 2

• decreases
• outer electron gets further from nucleus, electrostatic attraction reduced
• more electron shells, shielding increases

Question 3

What happens to the melting points as you go down Group 2 and why

Answer 3

• decreases
• size of atom increases
• in metallic lattice, delocalised electrons further away from the positive nucleus
• mass/charge ratio decreases

Question 4

State the equation for the reaction of a Group 2 metal and liquid water

Answer 4

M (s) + 2H2O (l) ➡️ M(OH)2 + H2 (g)

• produces a metal hydroxide and hydrogen gas

Question 5

State the equation for a Group 2 metal and steam

Answer 5

M (s) + H2O (g) ➡️ MO (s) + H2 (g)

• produces a metal oxide and hydrogen

Question 6

State the reactivity trend as you go down Group 2 and state why

Answer 6

Increases, due to decreased ionisation energy

Question 7

State the solubility trend of Group 2 metal hydroxides as you go down the group

Answer 7

• increases
  (Least soluble) Mg, Ca, Sr, Ba (most soluble)

Question 8

What happens to the solution the more soluble the hydroxide is and why

Answer 8

• becomes more alkaline (higher pH)
• when the hydroxide dissolves, it dissociate into OH- ions, making the solution alkaline

Question 9

Which solution is more alkaline and why
- Mg(OH)2
- Ba(OH)2

Answer 9

• Ba(OH)2
• because it is more soluble, so a larger amount dissolves
• more OH- ions present

Question 10

Why is Ca(OH)2 (lime) spread onto fields/soil

Answer 10

• acid rain can decrease the pH of soil too low for crops
• since it has low solubility, it can increase the pH of soil
• non-toxic

Question 11

Why is Mg(OH)2 (milk of magnesia) suitable as an indigestion remedy

Answer 11

• low solubility, so it’s pH isn’t too high
• can increase the pH of stomach, without damaging the oesophagus
• non-toxic

Question 12

Which 2 compounds are used to remove SO2 from chimney gases

Answer 12

• calcium oxide
• calcium carbonate

Question 13

State the solubility trend of Group 2 sulfates as you go down the group

Answer 13

• decreases
  (Most soluble) Mg, Ca, Sr, Ba (least soluble)

Question 14

How is barium sulfate used in medicine and why

Answer 14

• produces X-ray images of soft tissue after patient ingests a “barium meal”
• Ba ions have a high nuclear charge, absorb X-rays

Question 15

Why do barium meals not harm the patient, although Ba ions are highly toxic

Answer 15

• BaSO4 is insoluble
• cannot dissolve and cross into the bloodstream from the digestive system

Question 16

What would be seen on an X-ray if there was a leak in the patients digestive system after ingesting a barium meal

Answer 16

• BaSO4 would be seen in areas outside of the digestive system

Question 17

S

Question 18

State the 2 stages of extracting titanium from its ore

Answer 18

1. Ore reacted with Carbon and Chlorine gas, producing TiCl4 and CO
2. TiCl4 reacted with Mg under argon atmosphere at 1000°C for 2 days, producing 2MgCl2

Question 19

Why is Magnesium reacted with TiCl4 instead of Iron during the extraction of titanium from it’s ore

Answer 19

• a displacement reaction must occur
• Iron is less reactive than Tí, so would not displace it, instead
  TiCl4 + 2Mg ➡️ 2MgCl2 + Ti

Question 20

Why must the reaction of magnesium and titanium chloride be carried out under an argon atmosphere, during the extraction of titanium

Answer 20

• to prevent TiCl4 from reacting with O2 in the normal atmosphere and forming TiO2
• argon is inert, so no unwanted reactions