chapter 8

Question 1

Alkali metal common properties

Answer 1

• they are all reactive metals. Have to be stored under oil to stop them from reacting with oxygen and water vapor in the air
• they are soft and can be cut with a knife
• Like all metals, they form positive ions. The metals of group 1 form ions with a single positive charge
• as a result, the form compounds that have similar formula
• they all react strongly and directly with non metals to form salts. These salts are all white, crystalline, ionic solids that dissolve in water

Lithium least reactive - caesium most reactive

Question 2

Group 1 reaction with water

Answer 2

Reaction spontaneously with water to produce hydrogen gas and the metal hydroxide (exothermic)

Question 3

Lithium reaction with air and water and flames

Answer 3

Water: reacts steadily (metal doesn’t melt and hydrogen doesn’t ignite)
Air: tarnishes slowly to give a layer of oxide
Flame: red

Question 4

Sodium reaction with air and water and flames

Answer 4

Water: reacts strongly (melts, if sodium free to move - hydrogen doesn’t not usually ignite. For sure ignites is sodium is restricted
Air: tarnished quickly to give a layer of oxide
Flame: yellow

Question 5

Potassium reaction with air and water and flames

Answer 5

Water: reacts violently
Air: tarnishes very quickly to give a layer of oxide
Flame: lilac

Question 6

Group 2 metals

Answer 6

Alkaline earth metals less reactive than group 1 but take part in a large range of reactions (produce characteristic flame colours

Magnesium - no colour
Calcium - brick red
Strontium - scarlet
Barium - Apple green

Question 7

Study tip

Answer 7

Magnesium is so reactive that when it burns it can react with nitrogen in the air as well as oxygen

Burning magnesium can reduce carbon dioxide to carbon if it is lowered into a gas jar of the gas

Question 8

Trends in reactivity

Answer 8

Reactivity of group 1 and 2 both increase downwards

Magnesium reacts very slowly when placed in cold water but much more vigorous reaction is obtained of stem is passed over heated magnesium

Question 9

Aluminum

Answer 9

Aluminum is the most common metal in the earths crust

Ore - bauxite

Electrolysis of motel aluminum oxide produces aluminum at the cathode

Question 10

Aluminum usefulness

Answer 10

• Light, strong and has good electrical conductivity, low density and good conductivity has lead to the use in overhead power lines
• It is usually alloyed with other metals such as copper
• It is protected from corrosion by the stable layer of aluminum oxide that forms on its surface example: used for window frames because they resist weathering

Question 11

The emit reaction

Answer 11

• The High reactivity of aluminum is used to extract some metals from their oxides in small quantities
• Reaction is used to weld together damaged railway lines Example of reduction-oxidation and is known as the term it reaction

Question 12

Analytical test for aluminum ions

Answer 12

Aluminum ions don’t give characteristic colour in the flame test. Must be detected by some other methods

If aluminum salt is dissolved in water and sodium hydroxide solution is added - a white ppt is formed

Others metal ions such as calcium and magnesium giving a white ppt so the test inconclusive. By adding excess sodium hydroxide the aluminum ppt will dissolve

Question 13

Coloured compounds

Answer 13

Group 1,2,3 usually give white ppt and dissolve in water giving a colourless solution