C9 - Group 2

Question 1

What happens to the atomic radius as you go down group 2?

Answer 1

It increases

Question 2

Why does atomic radius increase down a group?

Answer 2

Nuclear charge increases down the group, so does the number of shielding electrons therefore the effective nuclear charge remains constant.
The increase in radius is due to higher principal energy levels being filled, whose orbitals are located further from the nucleus

Question 3

What happens to the first ionisation energy down group 2?

Answer 3

It decreases

Question 4

Why does the first ionisation energy decrease down the group?

Answer 4

As it is easier to remove an electron
The nuclear charge increases down the group, but the number of shielding electrons and the distance of the valence electrons from the nucleus increase, which outweighs the increase in nuclear charge

Question 5

What happens to melting point down group 2?

Answer 5

The melting points of the elements decrease down group 2 apart form magnesium to calcium which increases

Question 6

Why does melting point decrease down a group?

Answer 6

The atomic radius increases which results in a weaker attraction between the positively charged metal ions and the delocalised electrons
so, less energy is required to break the metallic bonds and the melting point decreases

Question 7

What happens to the solubility of the group 2 hydroxides down the group?

Answer 7

The solubility of the group 2 hydroxides increases down the group

Question 8

How soluble are the Group 2 hydroxides?

Answer 8

Be(OH)2 = Insoluble
Mg(OH)2 = Sparingly soluble
Ca(OH)2 = Slightly soluble
Sr(OH)2 = Soluble
Ba(OH)2 = Soluble

Question 9

What is the use of Ca(OH)2?

Answer 9

In agriculture to raise the pH of the soil

Question 10

What is the use of Mg(OH)2?

Answer 10

Magnesium hydroxide is as an antacid in indigestion medicines for relief

Question 11

What happens to the solubility of the group 2 sulfates down the group?

Answer 11

The solubility of the group 2 sulfates decreases down the group

Question 12

How soluble are the Group 2 sulfates?

Answer 12

BeSO4 = Soluble
MgSO4 = Soluble
CaSO4 = Slightly soluble
SrSO4 = Insoluble
BaSO4 = Insoluble

Question 13

How do you test for sulphate ions?

Answer 13

Add a few drops of HCl in order to remove carbonate impurities, which would otherwise form a white precipitate
Add a few drops of barium chloride
If sulfates are present a white precipitate of barium sulfate will form

Question 14

What is the use of barium sulfate?

Answer 14

Barium sulfate is used as a radiocontrast agent to help take X-ray images of the digestive system

Question 15

How does reactivity change down group 2?

Answer 15

It increases as it is easier to remove outer electrons

Question 16

What happens when group 2 metals react with water?

Answer 16

They form metal hydroxides and hydrogen gas

Question 17

What happens when group 2 metal oxides react with water

Answer 17

They form metal hydroxides

Question 18

How does CaO or CaCO3 treat flue gases?

Answer 18

They can both be used to neutralise the acidic gases and remove sulfur dioxide from the flue gases
This makes them better for the environment

Question 19

What happens when group 2 metal carbonates are decomposed (thermal decomposition) ?

Answer 19

They form the metal oxide and carbon dioxide gas

Question 20

What happens to group 2 metal nitrates are decomposed (thermal decomposition)?

Answer 20

They form the metal oxide, nitrogen dioxide and oxygen.

Question 21

How is Mg used in the extraction of Ti?

Answer 21

TiCl4 + 2Mg = Ti + 2MgCl2
Displacement reaction

Question 22

What do precipitates does magnesium hydroxide form?

Answer 22

Mg(OH)2 forms a white precipitate

Question 23

Why do Sr(OH)2 and Ba(OH)2 never form a precipitate?

Answer 23

As they are fully soluble