AS - Group 2

Question 1

What are elements in Group 2 otherwise known as?

Why is this?

Answer 1

The Alkaline Earth metals

Because their oxides and hydroxides are alkaline

Question 2

What block of the periodic table do Group 2 elements belong to?

Answer 2

S block

Question 3

Are group 2 elements more or less reactive than group 1 elements?

Answer 3

Less

Question 4

Which element is not typical of the group and not considered in this topic?

Answer 4

Beryllium

Question 5

Why does atomic radius increase down group 2?

Answer 5

Because each element has an extra filled electron shell compared with the one above it

Question 6

How does electron arrangement change down group 2?

Answer 6

The elements all have electrons in an outer s-orbital. This becomes further away from the nucleus going down the group due to the extra inner shells.

Question 7

What is the structure of bonding in group 2 elements?

Answer 7

They all have a giant metallic structure surrounded by a sea of delocalised electrons from the outer electron shells.

Question 8

What happens to the melting points as you go down group 2?

Which is the anomaly and why?

Answer 8

Generally the melting point decreases.

This is because going down the group, the atoms get bigger so the outermost electrons are further from the nuclei. There is less attraction between the delocalised electron and nucleus so requires less energy to break this bond.

The anomaly is magnesium due to a change in the arrangement of metallic ions.

Question 9

What is the general trend of first ionisation energy of the elements going down group 2?

Explain why this is the case.

Answer 9

Decreases down the group.

Each element down group 2 has a extra electron shell compared to the one above so the inner shells shield the outer electrons from the attraction of the nucleus. The extra shell also means that the outer electrons are further away from the nucleus which also reduced the nucleus’ attraction. So it takes less energy to remove the outer electron.

Question 10

In all their reactions, how many electrons do elements from group 2 lose and what do they form?

Answer 10

Each loses 2 electrons to become an ion with a 2+ positive charge.

Question 11

What does a lower pH mean?

Answer 11

More acidic.

Question 12

In all their reactions, are group 2 elements oxidised or reduced and why?

Answer 12

Oxidised because they lose electrons.

Question 13

When a group 2 element is oxidised, what happens to it’s oxidation state?

Answer 13

It goes from 0 to +2

Question 14

When group 2 elements react with water, what is the trend in reactivity down the group?

Answer 14

Metals get more reactive going down the group.

Question 15

What do the group 2 metals produce when reacted with water?

Answer 15

A metal hydroxide and hydrogen.

Question 16

Why do the group 2 elements react more readily with water down the group?

Answer 16

Because their ionisation energy decreases.

Question 17

What is the trend in solubility of the group 2 hydroxides, going down the group?

Answer 17

They become more soluble down the group.

Question 18

In terms of solubility, what is magnesium hydroxide described as?

Answer 18

Sparingly soluble

Question 19

What properties make titanium metal useful?

What can titanium be used for?

Where is titanium found? What is the problem with this?

Answer 19

It’s strong, low density and has a high melting point so can be used in the aerospace industry and for making replacement hip joints.

It is commonly found in the Earth’s crust but is not easy to extract.

Question 20

Most metals are found in the Earth as oxides and can be extracted by reacting the oxide with carbon. Why can this method not be used for titanium?

How, instead, is titanium extracted?

Answer 20

Because the metal reacts with carbon to form titanium carbide, TiC, which makes the metal brittle.

Titanium oxide, TiO2, is first converted to titanium (IV) chloride, TiCl4, by heating it with carbon in a stream of chlorine gas. TiCl4 is the. Purified by fractional distillation before being reduced by magnesium in a furnace.

Question 21

What is the equation for the reaction of magnesium with titanium chloride?

Answer 21

TiCl4(l) + 2Mg(s) -> 2MgCl2(s) + Ti(s)

Question 22

How is magnesium hydroxide used in medicine why?

Answer 22

Used in some indigestion tablets as an antacid to neutralise excess stomach acid which can cause heartburn or indigestion.

Question 23

How does magnesium react with water and how does it react with steam?

What is formed when magnesium reacts with steam?

Answer 23

Very slowly with cold water but rapidly with steam.

Magnesium reacts with steam to form an alkaline oxide and hydrogen:

Mg(s) + H2O(g) -> MgO(s) + H2(g)

Question 24

What is calcium hydroxide sometimes called and what purpose does it have?

Answer 24

Slaked lime.

Can be used in agriculture to neutralise acidic soil to maintain the optimum pH level for the particular crops to grow.

Question 25

What are glue gases?

What can be used to remove acidic sulfur dioxide, which is harmful for the environment, from flue gases? What is the process for this?

Answer 25

Flue gases are the gases emitted from industrial exhausts and chimneys.

Powdered calcium oxide (lime, CaO) and calcium carbonate (limestone, CaCO3) can be used to remove sulfur dioxide in a process called wet scrubbing.

In this process, a slurry is made by mixing the CaO or CaCO3 with water. This is then sprayed onto flue gases producing the solid waste product, calcium sulfite.

Question 26

What are the equations for the reactions involved in wet scrubbing using CaO and CaCO3 respectively?

Answer 26

CaO(s) + 2H2O(l) + SO2(g) -> CaSO3(s) + 2H2O(l)

CaCO3(s) + 2H2O(l) + SO2(g) -> CaSO3(s) + 2H2O(l) + CO2(g)

Question 27

What is the trend in solubility for the sulfatos of the group 2 elements, going down the group?

Answer 27

Solubility decreases down the group.

Question 28

In terms of solubility, what is barium sulfato, BaSO4, described as?

Answer 28

Insoluble

Question 29

How is barium sulfato used in medicine?

Answer 29

It is taken by mouth as a barium meal, which is a suspension of barium sulfate. Barium sulfate is opaque to x-rays meaning that they won’t pass through it. When the patient drinks the barium meal, barium sulfate coats the tissues of the oesophagus, stomach and intestine making them show up on X-rays, showing the structure of the organs so that doctors can identify any problems.

Question 30

Barium compounds are highly toxic. Why is it safe to give a patient a barium meal?

Answer 30

Because barium sulfate is so insoluble so will not have any toxic affects on the patient.

Question 31

How is acidified barium chloride solution, BaCl2, used to test for sulfate ions?

Why does an acid need to be added first in this test?

Answer 31

Barium chloride must first be acidified using nitric or hydrochloric acid. Acidified barium chloride is then added to the solution in question, if sulfate is present then a white precipitate of barium sulfate is formed.

The addition of acid removes any present carbonate ions which would also produce a white precipitate (barium carbonate) which is indistinguishable from barium sulfate.