2.2- Group 2

Question 1

Give the trend of atomic radius down group 2

Answer 1

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

Question 2

Give the trend of melting points down group 2

Answer 2

Melting point decrease downthe group, the metallic bonding weakens as the atomic size increases, the distance between the positive ions and the delocalised electrons increases, therefore the electrostatic attractive forces between the positive ions and the delocalized electrons weaken

Question 3

Give the trend of 1st ionisation energies down a group

Answer 3

The outermost electrons are held more weakly becaue they are successively further away from the nucleus

The outer shell aslso becomes more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons

Question 4

Explain the group 2 reactions with oxygen, specifically Mg

Answer 4

The group 2 metals will burn in oxygen, and the reactivity of group 2 metals increase down a group

Mg burns with a bright white flame, and MgO is a white solid with a high melting point due to its ionic bonding

Mg will also react with oxygen without a flame, mg ribbon often has a thin layer of magenesium oxide on it whcih needs to be cleaned off by emery paper before doing reactions with the mg ribbon

Question 5

What are the reactions of the group 2 metals with water and what would you observe

Answer 5

Magnesium reacts in steam to prouduce magneisum oxide and hydrogen, the Mg would burn with a bright white flame

Mg will also react with warm water giving a different magenisum hyrdroxide product

The other group 2 metals react with cold waterr with increasing vigour down the group to form hydroxides

As you go down the group one would observe, fizzing, the metal dissolving, the solution heating up, and with calcium a white precipitate apprearing with less appearing as you go down a group

Question 6

Why can titanium not be extracted by carbon or electrolysis

Answer 6

Titanium cannot be extracted by carbon becaue titanium carbide would be formed rather that titanium, it cannot be extracted by electrolysis because it has to be very pure

Question 7

What are the steps in extracting titanium

Answer 7

TiO2 is converted to TiCl4 at 900c

The TiCl4 is purified by fractional distillation in an argon atmosphere

The Ti is extracted by Mg in an argon atmosphere at 500c

Question 8

Give the 2 equations for extracting titanium from TiO2

Answer 8

TiO2 + 2Cl2 + 2C > TiCl4 + 2 CO

TiCl4 + 2Mg > Ti + 2MgCl2

Question 9

Why is titanium expensive

Answer 9

. The expensive cost of Mg

. It is a batch process, makes expensive because the proces is slowerm energy is lost when the reactor is cooled after stopping

. Argon for the atmospherem, also need to remove the moisture as TiCl4 is susceptible to hydrolisis

. High temperature that is required in both of the steps

Question 10

What is the trend of solubility of hydroxides down group 2

Answer 10

Group 2 hydroxides become more soluble down the group, all the group 2 hydroxides when not soluble appear as white precipitate

Question 11

Give the usage for magneisum hydroxide and its solubility in water

Answer 11

Magenesium hydroxide is classed as insoluble in water

A suspension of magneisum hydroxide in water will appear slightly alkaline, so some hydroxide ions must have been produces

Magnesium hydroxide is used in medicine to reduce excess stomach acid and to also treat constipation

It is safe to use because it is so weakly alkaline

Question 12

Give the usage for calcium hydroxide and its solubility in water

Answer 12

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

It will appera more alkaline in water at a pH of 11 as it is more soluble, hence more hydroxide ions that are present

A solution of calcium hydroxide is called lime water, and is used as a test for carbon dioxide

Question 13

Give the solubility of barium hydroxide

Answer 13

Barium hydroxide would easily dissolve in water, the hydroxide ions that are present in the solution makes in strongly alkaline

Question 14

What is the general solublity of the group 2 sulfates as you go down

Answer 14

Group 2 sulfates become less soluble down the group, barium sulfate is the least soluble

Question 15

Explain how barium sulfate is used in medicine

Answer 15

If barium is used in medicine as a barium meal give to patients who needs x rays of their intestines, the barium absorbs the x rays and so the gut shows up on the x ray image, even through the compound is toxic it is sage to use here because of its low solubility, meaning it is not absorbed into the blood

Question 16

What happens when barium metal is reacted with sulfuric acid

Answer 16

It will only react slowly as the insoluble barium sulfate produced will cover the surface of the metal and act as a barrier to further attack

The same effect happens to a lesser extent with metals going up the group as the solublilty increasases

The same effect does not happen with other acids like HCL as they form soluble group 2 salts

Question 17

How do you test for the presence of a sulfate ion

Answer 17

Use BaCl2 that is acidified with hydrochloric acid

If it is added to a solution that contains sulfate ions a white precipitate of BaSO4 forms

Question 18

Why does HCl need to be used when using BaCl2

Answer 18

The HCl rects with carbonate impurities that are often found within saltws that would form a white barium carbonate precipitate which is a false result, you cannot use sulfuric acid as it contains sulfate ions and would also give a false result