Reacitvity Trends p

Question 1

Physical properties of group 2

Answer 1

Reasonably high melting and boiling pants

Light metals with LOW densities

Form colourless white compounds

Question 2

Ionisation energy - group 2

Answer 2

Decreases as you go down the group

More shielding, greater atomic radius

Ionisation energy decreases
MORE REACTIVE

Question 3

Reducing agents - group2.

Answer 3

Each group2. Element has 2 outer shell electrons

Group 2 metals loose 2 electrons to a 2+ ion, the other species gain and is reduced

Question 4

Redox reaction with oxygen (group 2)

Answer 4

React vigorously with oxygen to form a metal oxide ( general formula of MO)

2Mg + O2 — 2 Mg O

Question 5

Redox reactions with water ( group2 )

Answer 5

React with water to form an alkaline hydroxide
General formula M( OH)2
Hydrogen gas formed
Be- doesn’t react

Mg + H20 —- Mg(OH)2 + H2

Question 6

Redox reactions with dilute acids( group 2)

Answer 6

Form a salt and hydrogen gas
Exception of be

E.g. Mg + 2HCl— Mgcl 2 + H2

Question 7

Group 2 oxides/hydroxides as bases?

Answer 7

Metals are bases( most are soluble so they’re alkalis too)

The group2 oxides react with H20=- metal hydroxides , which dissolve. Make the solution STRONGLY alkaline - releasing OH- ions

Question 8

What is an exception for oxides of group2 metals

Answer 8

Magnesium oxide reacts SLOWLY and the hydroxide isn’t very soluble

Question 9

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

Answer 9

Solubility INCREASES
Resulting solutions contain more OH- IONS, AND ARE more alkaline
Mg(OH)2 - slightly soluble in h20, the solution has a low OH- concentration and a ph of 10
Ba( OH)2 - more soluble in h20- solution has a greater OH- concentration and a ph - 13

SOLUBILTIY, PH AND ALKLAINITY INCREASES

Question 10

Group2 compounds( bases) in agriculture

Answer 10

Calcium hydroxide( Ca(OH)2), added to fields as lime my farmers to increase the Ph of acidic soils 
The calcium hydroxide neutralises acids in the soil forming water

Question 11

Medicine - group2 compounds as bases

Answer 11

Group 2 bases often used for antacids for relating acid indigestion
Many indigestion tabs use magnetism hydroxidea nd calcium carbonates -

Acid in stomach = Hcl
Mg(OH)2 + 2HCl—– 2H20 + MgCL

Question 12

The halogens- chlorine

Answer 12

Green gas, Poisionesss in high concentrations

Question 13

Flurorine

Answer 13

Pale yellow gas

Question 14

Bromine

Answer 14

Red liquid that goes off dense brown Poisionesss fumes

Question 15

Iodine

Answer 15

Shiny grey solid - sublimes to purple gas

Question 16

Trend in melting and boiling point - halogens

Answer 16

More electrons as you descend
Stronger London dispersion forces between the molecules
More energy required to break these intermolecular forces
Boiling point INCREASES

Question 17

Trends in reactivity

Answer 17

Halogen atoms react by gaining an electon in p subs hell to form 1- ion
- they are REDUCED - oxidise another substance
- DESCENDING the group, atomic radius increases, outer electrons are further from the nucleus, outer shell electrons are also shielded move from the attraction of the positive nucleus because of inner electrons
Harder for large atoms to attract electron = less reactive

Question 18

Halogen- halide displacement, what happens hen a halogen is added to a halid in a solution

Answer 18

If the halogen is MORE reactive - reaction takes place,
Halogen displaces the halide for the solution

Chlorine displaces both bromine and iodine, but iodine doesn’t displace ether

Question 19

Chlorine in h20 and organic solvent?

Answer 19

Pale green

Question 20

Bromine in h20 and organic solvent?

Answer 20

Orange

Question 21

Iodine in water and organic solvent

Answer 21

Brown in h2o

Purple in organic solvent

Question 22

Fluorine

Answer 22

Pale yellow gas

Reacts with almost any substance

Question 23

Astatine

Answer 23

Rare

Radioactive - decays rapidly

Question 24

Disproportion - halogens

Answer 24

Redox reaction
Same element oxidised an deduced

Reaction of heroine wit h20 and cold, dilute sodium hydroxide

Question 25

Chlorine + sodium hydroxide

Answer 25

BLEACH 2NaOH+ Cl2 --- NaClO + NaCl 2 + H20

Question 26

Chlorine+ water

Answer 26

Cl2+ h20 -- Hcl+ Hcl0 | Hcl0+ H20-- Clo- + H30+ aqueous caloric acid ionises to make chlorite ions that kill bacteria

Question 27

Chronicled water- PROS

Answer 27

Kills disease-causing microorganism Some chlorine remains in H20- prevents reinfect ion further down the supply Prevents algae growth, eliminating bad smell and taste, removing discolouration caused by organic compiunds

Question 28

Cons of chlorinated water

Answer 28

Harmful if breathed in ( gas)- respiratory irritant Liquid form = chemical burn If reacts with organic compounds- chlorinated hydrocarbons( CANCER CAUSING)

Question 29

Alternatives to chlorinated water

Answer 29

Purification tablets UV light- ineffective in cloudy water and won't stop water being infected further own the line, BUT kills microorganism by DNA damaging OZONE- Strong oxidising agent, kills microorganisms

Question 30

Carbonate ion?

Answer 30

CO3 ... 2-

Question 31

Carbonate ion test

Answer 31

Add dilute acid e.g, Hcl to form CO2 Bubble the gas through lime water and it will turn CLOUDY( ca(Oh)2) Co2 forms a fine white precipitate of calcium carbonate, whihc is what turns the water Cloudy ( carbonate+ acid-- co2 and water)

Question 32

Sulphate ion?

Answer 32

So4 2-

Question 33

SULFATE ion test

Answer 33

Most Sulphates are soluble in water BUT barium sulphate is insoluble - forms a white precipitate Add dilute Hcl( ensure carbonate ions are removed ) and barium chloride Ba 2+. + SO4 2- -------BaSO4

Question 34

Halide ions test

Answer 34

Most halides are soluble in h2o but silver halides are INSOLUBLE Aqueous silver ions react with aqueous halide ions to produce precipitates of silver halides Add aqueous silver nitrate( Ag No3) to an aqueous solution fo a halide add aqueous ammonia if the colour is hard to distinguish

Question 35

Chloride , bromine and iodine colours- halide test

Answer 35

Chlorine- white, soluble in dilute NH3 Bromine- cream, soluble in concentrated NH3 Iodine - yellow, insoluble in concentrated NH3

Question 36

Ammonia

Answer 36

Nh3

Question 37

Ammonium ions

Answer 37

NH4 +

Question 38

Ammonium ions test

Answer 38

Ammonia gas ( NH3) is alkaline, so you can check for it suing a damp piece of red litmus paper - turns it red Add naOH and warm the mixture NH4 + + OH- ----- NH3 + H20

Question 39

False positives?

Answer 39

Barium carbonate is a white and insoluble in h20, Oslo if you carry out the SULFATE test on a carbonate, youll get a white precipitate too, barium sulphite = same m need to ensure there's no carbonate first Silver carbonate and silver sulphate are both insoluble in h20 - form as precipitates in. This test( AgNO3 forming white precipitate)

Question 40

Order of tests

Answer 40

Carbonate, sulphate then halide

Question 41

Mixture of ions - describe doing tests and why it works in this order

Answer 41

1. CARBONATE test= if you see bubbles, continue adding dilute nitric acid until bubbling stops, all carbonate ions removed 2. SULFATE test = add an excess of Ba(NO3)2, any sulphate ins present will precipitate as barium SULFATE- filter solution to remove 3. HALIDE test= Add AgNO3, any carbonate or sulphate ions initially present have been removed