Topic 4- Inorganic chemistry and the periodic table

Question 1

What are group 2 elements?

Answer 1

Group 2 are metals that form 2+ ions when they react. All group 2 metals have electron configurations that end s 2

Question 2

Trends of Group 2 elements

Answer 2

The atomic radius increases when you go down group 2. This means the first ionisation energy decreases when we go down group 2 because there is more shielding meaning weaker attraction between the nucleus and outer electrons.
This makes it easier to remove the outer electron and so less energy is required

Question 3

What happens when group 2 elements react with water?

Answer 3

Group 2 elements react with water to form bases. The reaction with water to form metal hydroxides. The reactivity increases with water when you go down. When magnesium reacts with steam more vigorously and forms magnesium oxide instead of hydroxide

Question 4

What happens when group 2 elements react with oxygen?

Answer 4

Group 2 elements react with oxygen to form a base. The reaction with oxygen to form metal oxides. Group 2 oxides are white solids

Question 5

What happens when group 2 elements react with chlorine?

Answer 5

Group 2 elements react with chlorine to form chlorides. Reaction with chlorine to form metal chlorides.

Question 6

What happens when group 2 oxide react with water?

Answer 6

Group 2 oxides form bases when reacted with water. Alkaline solutions formed when added to water

Question 7

What is the trend in solubility of group 2 hydroxides?

Answer 7

They become more strongly alkaline as you go down the group as the hydroxides become more soluble

Question 8

What is the trend in solubility of group 2 sulfates?

Answer 8

Group 2 sulfates solubility decreases when you go down the group

Question 9

What is the test for carbon dioxide?

Answer 9

Lime water turns cloudy as white precipitate form when carbon dioxide is present

Question 10

What is the test for hydrogen?

Answer 10

Hydrogen ignites in the air. If hydrogen I present in a test tub a lighted splint creates a squeaky pop

Question 11

What is the test for oxygen?

Answer 11

A glowing splint will re-ignite in the presence of oxygen

Question 12

What is thermal stability?

Answer 12

Thermal stability is a measure of the extent to which a compound decomposes when heated

Question 13

What happens when a Group 2 carbonate thermally decomposes?

Answer 13

The carbonate breaks down into metal oxides and carbon dioxide

Question 14

What happens when a group 2 nitrate thermally decomposes?

Answer 14

The nitrate breaks down into metal oxides, nitrogen dioxide and oxygen if brown fumes are observed. If not the nitrate breaks down into metal nitrate and oxygen

Question 15

What are the trends in thermal stability?

Answer 15

Carbonates and nitrates become more thermally stable as you go down group 2

Question 16

Why do carbonates and nitrates become more thermally stable as we go down group 2?

Answer 16

Near the top of group 2 elements have a high charge density which means the charge is less spread over an area. This distorts the electron cloud of the nitrate and carbonate so it is less stable. When you go down the group there is a low charge density so it is more thermally stable

Question 17

What are the trends in thermal decomposition in group 1 carbonates?

Answer 17

Group 1 carbonates thermally decompose and are more thermally stable than group 2 compounds. Except for lithium carbonate which has a high charge density which distorts the electron cloud making it less stable

Question 18

What are the trends in thermal decomposition in group 1 nitrates?

Answer 18

Group 1 nitrates break down into nitrites and oxygen. Except for lithium nitrate which decomposes to form lithium oxide, nitrogen dioxide and oxygen

Question 19

How do you conduct the flame test?

Answer 19

• Dip nichrome wire in concentrated HCL
• Dip into the sample
• Hold the end of the wire in the flame and observe the colour

Question 20

What is the flame test?

Answer 20

The flame test is a chemical test that identifies the presence of a cation in a compound

Question 21

Flame test colours

Answer 21

Lithium- red
Sodium- yellow 
Potassium- lilac 
Rubidium- red/purple 
Caesium- violet
Beryllium- no colour 
Magnesium- no colour
Calcium- red
Strontium- red
Barium- green

Question 22

What cause the colour in the flame test?

Answer 22

When electrons absorb energy they get excited and move to a higher energy level. This movement is immediately followed by the electrons moving to a lower energy level (ground state) which releases energy. This energy corresponds to the radiation in the visible light spectrum hence a colour is seen.

Question 23

What is the test for ammonium ions?

Answer 23

Ammonium ions is added to sodium hydroxide to form ammonia which has pungent smell but it turns damp red litmus paper blue

Question 24

Halide displacement reactions?

Answer 24

• chlorine displaces bromine and iodine
• bromine displaces iodine but not chlorine
• iodine doesn’t displace either chlorine or bromine

Question 25

What happens when sulphuric acid is added to sodium chloride?

Answer 25

Misty fumes - hydrogen chloride

Question 26

What happens when sulphuric acid is added to sodium bromide?

Answer 26

Mist fumes- hydrogen bromide
Brown fumes- bromine
Colourless gas choking smell- sulfur dioxide

Question 27

What happens when sulphuric acid is added to sodium iodide?

Answer 27

Misty fumes- hydrogen iodide
Purple fumes or black solid- iodine
Yellow solid- sulfur
Colourless gas rotten egg smell- hydrogen sulfide

Question 28

Halide ions in nitrate solution

Answer 28

Chlorine ions- white precipitate
Bromine ions- cream precipitate
Iodine ions- yellow precipitate