3.2.2 Group 2, the alkaline earth metals

Question 1

why are the group 2 Metals called the alkali earth metals

Answer 1

their oxides and hydroxides are alkaline

Question 2

describe the electron arrangement of all the group 2 metals

Answer 2

all have 2 outer electrons in their s orbital

Question 3

describe how atomic radius changes

Answer 3

going down group it increases, each element below has an extra filled main level of electrons

Question 4

describe and explain the trend in melting point - group 2

Answer 4

. going down group electrons are further away from positive nuclei
. so strength of metallic bond decreases going down group
. therefore decrease in mp going down group
. mg has lowest mp and is an anomaly

Question 5

describe and explain the trend in ionisation energies

Answer 5

both the first and second ionisation energies decrease going down group
. as outer 2 electrons get further away from nucleus and so less attracted

Question 6

how does reactivity change in the group 2

Answer 6

increases going down group, as the first and second ionisation energies decrease

Question 7

how do the group 2 metals react with water

Answer 7

each forms a metal hydroxide and hydrogen with cold water
. mg reacts slowly with cold water but rapidly with steam to form MgO and hydrogen
. same reactions but getting more vigorous going down group

Question 8

what are the uses of magnesium hydroxide

Answer 8

milk of magnesia - used to neutralise excess stomach acid to treat heartburn and indigestion

Question 9

what are the uses of calcium hydroxide

Answer 9

slaked lime - used to treat acidic soil in agriculture so soil had optimum pH for plant growth

Question 10

how is Mg used to extract Ti

Answer 10

. Titanium oxide reacted with Cl and coke (carbon) to form TiCl4 and CO
. Titanium chloride reduced to Titanium by reaction with Magnesium, which displaces the Ti to form MgCl2

Question 11

how are CaO and CaCO3 used in power stations

Answer 11

used to remove SO2 from flue gases
An alkaline slurry made from calcium oxide (lime) and water is sprayed into to the flue gas to form calcium sulfite which can be further oxidized to form calcium sulfate also known as gypsum
- gypsum is a sale-able product and is used to make builders’ plasterboard and plaster
CaO (s) + 2H20 (l) + SO2 (g) —-> CaSO4*2H20(s)

Question 12

how do all the group 2 hydroxides look

Answer 12

white solids

Question 13

what is the trend in the solubility of the G2 hydroxides

Answer 13

going down the group they become more soluble
. Mg(OH)2 is sparingly insoluble
. calcium hydroxide is more soluble
. strontium hydroxide is more soluble
. barium hydroxide dissolves to produce a strongly alkaline solution of Ba2+ ions and OH- ions

Question 14

describe the trend on the solubility of the G2 sulphates

Answer 14

. become less soluble going down the group
. Barium sulphate is insoluble

Question 15

what are some uses of barium sulphate

Answer 15

Barium sulphate is insoluble, so can be ingested to outline the gut in medical X-rays
. can also use it to test for sulphate ions: acidify a solution using HCl then add BaCl2, if sulphate ions are present a while precipitate will form - the insoluble barium sulphate

Question 16

why is the solution acidified in the test for sulphate ions with BaCl2

Answer 16

the acid removes carbonate ions as CO2 as barium carbonate is also a white precipitate

Question 17

do the metals effervesce when added to water

Answer 17

They release hydrogen gas

Question 18

Explain why calcium has a higher melting point than strontium

Answer 18

1. The delocalised electrons are closer in calcium
2. So there is stronger metallic bonding

Question 19

State why sulfuric acid should not be used to acidify the barium chloride

Answer 19

Contains sulfate ions so would form a white precipitate

Question 20

State how barium sulfate is used in medicine. Explain why this use is possible, given that solutions containing barium ions are poisonous

Answer 20

1. Barium meal given and used as a contrast medium for X-rays
2. Barium sulfate is insoluble

Question 21

State why magnesium hydroxide solution could not be used in the titration of weak acids

Answer 21

it is insoluble

Question 22

Use your knowledge of the reactions of Group 2 metals with water to explain why water should not be used to put out a fire in which magnesium metal is burning

Answer 22

1. Hydrogen would be produced
2. Which is flammable and so has a risk of explosion

Question 23

Describe and explain the trend in reactivity of the group 2 metals with cold water

Answer 23

1. Reactivity increases down the group
2. The outer electrons are more easily lost down the group
3. Due to the increased distance and shielding

Question 24

Group 2 - alkaline metals

Answer 24

Form 2+ ions
Ar increases as you go down as extra electron shells
Reactivity increases as go down as more shielding so easier to loose electrons
Ionisation energy decreases
Melting point decreases as intermolecular forces have to act over a much greater distance

Question 25

Reactions between water and alkaline metals

Answer 25

Redox reaction form metal hydroxides and hydrogen gases
Eg Mg is oxidised
Mg reacts slowly but fast with steam
Bright white flame to make a bright white powder

Question 26

Flue gas removal equation

Answer 26

Ca0 +2h20 +so2 → caso3 +2h20

Question 27

mg reaction with steam

Answer 27

Mg(S) + H2O(g) -> MgO(s) +H2(g)