8.1 - Group 2

Question 1

What are group 2 elements commonly referred too ?

Answer 1

Alkaline earth metals

Question 2

What are the ions forms by group 2 atoms ?

Answer 2

2+

Question 3

How many electrons will group 2 atoms lose to form ions ?

Answer 3

2

Question 4

In reactions are group 2 atoms reduced or oxidised ?

Answer 4

Oxidised

Question 5

In reactions what do group 2 elements later act as ?

Answer 5

Reducing agents

Question 6

How many electrons do they have in their S sub shell ?

Answer 6

2

Question 7

State the equation for the reaction of group 2 elements with oxygen

Answer 7

Group 2 element + oxygen —> metal oxide

Question 8

State the equation for the reaction of group 2 elements with water

Answer 8

Group 2 element + water —> alkaline hydroxide + hydrogen

Question 9

State the equation for the reaction of group 2 Elements with dilute acids

Answer 9

Metal + acid —> salt + hydrogen

Question 10

State the trend in reactivity down group 2

Answer 10

Reactivity increases down the group

Question 11

State the trend in ionisation energies down group 2 and state why

Answer 11

• ionisation energy decreases down the group because the attraction between the nucleus and outer electron decreases
• as a result of increasing atomic radius and increasing shielding

Question 12

State what occurs during the reaction of group 2 metal oxide and water

Answer 12

Hydroxide ions are released, forming alkaline solutions of the metal hydroxide

Question 13

State what occurs to the metal oxide and water reaction when the solution becomes saturated

Answer 13

Metal and hydroxide ions will form a solid precipitate

Question 14

How can you see from their reactions that reactivity increases down the group ?

Answer 14

Reactions will be faster and more vigorous

Question 15

Why does reactivity increase down group 2 ?

Answer 15

• atomic radius increases —> more shells
• increasing shielding —> more inner shells
• less nuclear attraction despite increased nuclear charge
  = less energy to remove outer electrons

Question 16

Show the reaction of magnesium with oxygen and explain what occurs

Answer 16

2Mg (s) + O2 (g) —> 2MgO (s)
0 ———————> +2 = oxidation
0 ————> -2 = reduction

The total changes in oxidation number balance :

• 2 Mg in 2Mg = each Mg increases by +2 = total increase = +4
• 2 O in O2 = each O decreases by -2 = total decrease = -4

Question 17

What is the general formula for group 2 elements with water

Answer 17

X (OH)2 + hydrogen gas

Question 18

Explain the reaction with Sr and water and state the balanced equation

Answer 18

Sr (s) + 2H2O (l) —> Sr(OH)2 (aq) + H2 (g)
0 —> +2 = oxidation
+1 ———————> 0 = reduction

Not all the hydrogen atoms are reduced :

• 1 Sr in Sr —> Sr increases by 2 = total increase = +2
• 4 H in 2H2O ——> 2 H decrease by 1 forming H2 = total decrease = -2
  2 H do not change forming Sr(OH)2

Question 19

Explain the reaction of Magnesium and diluted hydrochloric acid and state the equation

Answer 19

Mg (s) + 2HCl (aq) —> MgCl2 (aq) + H2 (g)
0 —> +2 = oxidation
+1 —> 0 = Reduction

The total changes I’m oxidation number balance :

• 1 Mg in Mg = Mg increases by 2 = total increase = +2
  2 H in 2HCl = each H decreases by 1 = total decrease = -2

Question 20

How does the solubility and alkalinity of group 2 hydroxides change down the group ?

Answer 20

Increases

Question 21

Give an example of group 2 oxide with water

Answer 21

CaO (s) + H2O (l) ———-> Ca^2+ ( aq) + 2OH- (aq)

Question 22

How does the pH of resulting solutions from group 2 hydroxides change down the group ?

Answer 22

Increases

Question 23

Explain the solubility of group 2 hydroxides in water ?

Answer 23

• increases down the group
• therefore resulting solutions contain more OH- (aq) ions and are more alkaline
• Mg(OH)2 is only very slightly soluble in water = solution has a low OH- (aq) concentration and a pH = 10
• Ba(OH)2 (s) is much soluble in water = solution has a greater OH- (aq) concentration and a pH = 13

Question 24

What is the trend in alkalinity in group 2 hydroxides ?

Answer 24

• solubility increases
• pH increases
• alkalinity increases

Question 25

How can you show this trend in an experiment ?

Answer 25

• add a spatula of each group 2 oxide to water in a test tube
• shake the mixture —> on this scale there is insufficient water to dissolve all of the metal hydroxide that forms = you will have a saturated solution of each metal hydroxide with some white solid undissolved at the bottom of the test- tube
• measure the pH of each solution —> the alkalinity will be seen to increase down the group

Question 26

What is the general use of group 2 compounds ?

Answer 26

Neutralising acids

Question 27

What is the group 2 compound calcium hydroxide used for ?

Answer 27

• used in agriculture to neutralise acidic soils by increasing their pH
• added to fields as limes by farmers —> increase pH
• calcium hydroxide neutralises acid in the soil forming neutral water

Question 28

What is the equation for the reaction of calcium hydroxide neutralising water to form neutral water ?

Answer 28

Ca ( OH)2 (s) + 2H+ (aq) —> Ca2+ (aq) + 2H2O (l)

Question 29

What are group 2 bases often used for in medicine ?

Answer 29

Often used as antacids to treat acid indigestion

Question 30

What are the group 2 compound’s magnesium hydroxide and calcium carbonate used for in medicine?

Answer 30

Used in antacids to treat acid indigestion by neutralising acids that cause indigestion eg. HCl

Question 31

What is milk of magnesia ?

Answer 31

Suspension of white magnesium hydroxide in water

Question 32

State the equation for magnesium hydroxide in antacids

Answer 32

Mg(OH)2 (s) + 2HCl (aq) —> MgCl2 (aq) + 2H2O (l)

Question 33

State the equation for calcium carbonate In antacids

Answer 33

CaCO3 (s) + 2HCl (aq) —> CaCl2 (aq) + H2O (l) + CO2 (g)