Group 2 metals

Question 1

What happens to atomic radius as you go down group 2?

Answer 1

atomic radius increases due to more filled energy shells, so the outer electrons get further away from the nucleus

Question 2

What happens to ionisation energy as you go down group 2?

Answer 2

as you go down group 2 ionisation energy decreases, due to greater atomic radius and greater shielding, so electrons are attracted less strongly to the nucleus

Question 3

What happens to melting point as you go down group 2?

Answer 3

generally decreases down group 2, due to increased atomic radius. increased atomic radius decreases charge/size ratio of the ion which results in weaker metallic bonding, so less energy is required to break the metallic bonds

Question 4

How does Mg react with cold water?

Answer 4

very very slowly

Question 5

How does Mg react with steam?

Answer 5

reacts readily with steam

Question 6

What is the equation for Mg reacting with steam?

Answer 6

Mg(s) + H2O(g) –> MgO(s) + H2(g)

Question 7

How does Ca, St, Ba react with cold water?

Answer 7

vigorously

Question 8

What is the general equation for the reaction of Ca/St/Ba with cold water?

Answer 8

Xx(s) + 2H2O(l) –> Xx(OH)2 (aq) + H2(g)

Question 9

What is a property of Ca(OH)2?

Answer 9

is only sparingly soluble in water so is used as limewater to test for CO2 gas

Question 10

What happens to the solubility of group 2 hydroxides as you go down the group?

Answer 10

solubility of the hydroxides increases as you go down the group

Question 11

What does Ba(OH)2 form?

Answer 11

a colourless solution

Question 12

What is Mg(OH)2 described as in water?

Answer 12

sparingly soluble

Question 13

Why is it that the more soluble the hydroxide, the stronger the alkali?

Answer 13

higher concentration of OH- ions

Question 14

What is Mg (OH)2 used for?

Answer 14

as an indigestion medication/antacid as it is a weak alkali so will neutralise excess stomach acid without being corrosive

Question 15

What is Ca(OH)2 used for?

Answer 15

in farming as a soil as an additive to increase pH

Question 16

Why can titanium not be extracted by reduction with carbon?

Answer 16

because titanium carbide forms, which makes the metal brittle and useless

Question 17

What does reduction of titanium with more reactive metals cause?

Answer 17

impurity problems and it is difficult and expensive to eliminate the reducing agent from the titanium

Question 18

What is step 1 in obtaining Ti?

Answer 18

conversion of titanium(IV) oxide into titanium(IV) choride
-by reaction with chlorine and coke at 900C
-titanium(IV) chloride is a liquid at room temperature so can be purified by fractional distillation

Question 19

What is step 2 in obtaining Ti?

Answer 19

reduction of titanium(IV) chloride by adding a reactive metal
-usually sodium in the UK
-the temperature of the sodium is initially set at 550C but the exothermic reaction raises it to nearly 1000C during the reaction

Question 20

Why is step 2 carried out in an inert atmosphere of argon?

Answer 20

to prevent any contamination of the Ti with oxygen or nitrogen

Question 21

How is the sodium by-product removed?

Answer 21

washing with dilute HCl leaving granules of titanium behind)

Question 22

What else can be used as the reducing agent for the obtainment of Ti?

Answer 22

magnesium
high temp and inert argon atmosphere

Question 23

What happens to the solubility of the group 2 sulfates as you go down the group?

Answer 23

solubility of the sulfates decreases as you go down the group

Question 24

What is special about BaSO4?

Answer 24

it is insoluble in water

Question 25

How do we test for sulfate ions?

Answer 25

using a solution containing barium ions like BaCl2
-add dilute hydrochloric acid
-add BaCl2
-a white precipitate of BaSO4 is formed if there are sulfate ions present

Question 26

Why must the BaCl2 solution be acidified first before removing carbonate ions?

Answer 26

carbonate ions interfere with the test as they can also form a white precipitate of barium carbonate

Question 27

Why can’t you use sulfuric acid?

Answer 27

it contains sulfate ions so would form a white precipitate

Question 28

What is a medical use of BaSO4?

Answer 28

in a barium meal
-BaSO4 blocks xrays and is not toxic as it is insoluble in water and bodily fluids
-aqueous suspension of it is taken and it coats the digestive tissues so they show up on x-rays

Question 29

Why can’t other compounds of barium be used in a barium meal?

Answer 29

they’re poisonous