Alkaline earth metals (group 2) 9

Question 1

size

Answer 1

increase down a group

Question 2

melting point

Answer 2

high (decrease apart from Mg)

sea of delocalised electrons are further way from the positive nucleus

Question 3

reaction with water

Answer 3

more reactive going down the group
redox reaction

Mg(s) +2H20(l) —— Mg(OH)2 (aq) + H2 (g)

(magnesium hydroxide is milk of magnesia and is used to neutralise excess stomach acid)

Mg(s) +H20(g) —— MgO + H2(g)

(reacts rapidly wth stream)

Question 4

hydroxide

Answer 4

magnesium hydroxide = (insoluble)
calcium hydroxide = (sparingly soluble) = limewater
strontium hydroxide= (more soluble)
barium hydroxide = dissloves = strong alkaline solution

Question 5

sulfate

Answer 5

less soluble going down the group

barium sulphate = outline the gut in x-ray (insoluble)

Question 6

test for sulphate ions

Answer 6

acidified with nitric/hydrochloric acid
if a sulphate is present a white precipatiate is formed

adding acid removes carbonate ion as carbon dioxide

Question 7

atomic radius

Answer 7

decrease across a period

Question 8

Na / Mg / Al

Answer 8

metals
metallically bonded
more delocalised electrons (stronger bonds)
(increased positive charge=more delocalised electrons = decreasing radius)

Question 9

Si

Answer 9

macromolecular
strong covalent bonds
lots of energy needed to break the the bonds = high melting point

Question 10

p / S /Cl

Answer 10

melting point depends on the van Der walls
more molecules= more van der walls
weak and easy to overcome

Question 11

Ar

Answer 11

noble gas

Question 12

general trend in first ionisation energy

Answer 12

general trend = increase

increasing attraction between the outer shell electrons na the nucleus, due to the number of protons

Question 13

alkaline earth metals

Answer 13

atomic radius= increase = more shells
first ionisation energy = decrease
reactivity = lose on electron = positive ion
melting point = generally decrease

Question 14

atomic radii of the group 2 elements

Answer 14

increase
another full shell added each time
shells repel each other

Question 15

melting point of group 2

Answer 15

decrease
attract of the positive decrease because the distance increase
delocalised electron further from nucleus
strength of metallic bonds decrease

Question 16

ionisation energy of group 2
Be 900
Mg 738
Ca 590
Sr 550
Ba 503

Answer 16

decrease
easier to lose an electron
distance increase so the delocalised electrons further away, so is easier to remove

Question 17

magnesium

uses and reasons

Answer 17

extraction of titanium
reduces
added to iron to remove sulphur
more reactive so would displace the iron

Question 18

magnesium hydroxide Mg(OH)2

uses and reasons

Answer 18

treating acid indigestion
increase water (reduces acid)

Question 19

claim hydroxide Ca(OH)2

uses and reasons

Answer 19

neutralise the soil

strong base

Question 20

calcium hydroxide solution Ca(OH)2 (aq)

uses and reasons

Answer 20

limewater

test fro carbon dioxide

Question 21

Barium sulfate BaSO4

Answer 21

main source of commercial barium
test for sulfate ions

coats the inside of intestines so they show up better on the x-ray

Question 22

uses go magnesium in the extraction of titanium from TiCl4

Answer 22

TiCl4 (l) + 2Mg(s) —- 2MgCl2 (s) + Ti (s)

used in the aerospace industry and in replacement of hips

Question 23

explain how BaSO4 is insoluble

Answer 23

white precipitate

insoluble

Question 24

lime kilns

Answer 24

CaCO3 (s)—- CaO(s) + CO2(g)
uses 25 tones of limestone
unlike to be 100% pure
lime (CaO) and slaked lime (Ca(OH)2) used to neutralised soil
CaO(s) + 2HCl (aq) —– CaCl2 (aq) + H20 (l)
Ca(OH)2 (s) + 2HCl (aq) —– CaCl2 (aq) + 2H2O (l)

Question 25

test for sulfate ions

Answer 25

use acidified BaCl2