periodicity

Question 1

Group 2 compound + water?

Answer 1

= Metal hydroxide and hydrogen (gets quicker down the group)

Question 2

Metal hydroxide solubility?

Answer 2

Mg(OH)2 is the least soluble, Ba(OH)2 is the most

Question 3

Metal Sulfate solubility?

Answer 3

BaSO4 is insoluble, MgSO4 is most soluble

Question 4

Test for SO4 ions?

Answer 4

add HCL and BaCl2 to solution

- If SO4 present = white ppt (BASO4)

Question 5

F2, Cl2, Br2, I2?

Answer 5

F2 = pale yellow gas
Cl2 = Green gas
Br2 = Red brown liquid
I2 = Grey solid

Question 6

Uses Of BaSO4

Answer 6

Barium meal (opaque on Xrays)

Question 7

Use of CaO/ CaCO3

Answer 7

Scrubbing

Eg CaO + water + SO2 –> CaSO3 + water

Question 8

Uses of Ca(OH)2

Answer 8

Neutralises acidic soil

Question 9

Uses of Mg(OH)2

Answer 9

Anacid (neutralises stomach acid)

Question 10

Use of Chlorine?

Answer 10

NaOH + Cl2 –> NaClO + NaCl

Bleach

Question 11

Use of chlorine? - disproportionation

Answer 11

1) Cl2 + water –> 2H+ + Cl- + ClO- (these ions kill bacteria, so used in water treatment)
2) Cl2 + water –> 2H+ +2Cl- + 0.5 O2 (sunlight)

Question 12

Halide ion precipitates

Answer 12

AgCl = White ppt (dissolves in dilute Ammonia)
AgBr = Cream ppt (dissolves in c. ammonia)
AgI = yellow ppt (insoluble)

Question 13

Why is nitric acid added before halide ion identification?

Answer 13

To remove carbonate ions

Question 14

Use of magnesium solid?

Answer 14

1) Mg + TiO2 –> TiCl4 (carbon solid, Cl2, heat)
2) fractional distillation of TiCl4
3) TiCl4 + 2Mg –> Ti + 2MgCl

Question 15

Halides = H2SO4?

Answer 15

Eg NaX + H2SO4 –> NaHSO4 + HX

Question 16

What do HF and HCl reduce H2so4 to?

Answer 16

Nothing

Question 17

What does HBr reduce H2SO4 to?

Answer 17

SO2

Question 18

What does HI reduce H2S to?

Answer 18

SO2, H2s, S

Question 19

observations with reduction of H2SO4?

Answer 19

Br2 = orange fumes
SO2 = Choking gas
I2 = brown solid
S = yellow powder
H2S = rotten egg smell

Question 20

Flame test?

Answer 20

burn nichrome wire with unknown compound (clean wire with HCl first)
Ca 2+ = brick red flame
Sr 2+ = red flame
Ba 2+ = pale green flame

Question 21

Test for ammonium ions?

Answer 21

turns red litmus paper turns blue (have to make it into NH3 first by heating ammonium ions)

Question 22

Test for Carbonate ions?

Answer 22

Add HCl = fizz (bubble through limewater etc)

Question 23

test for OH-?

Answer 23

red litmus paper or universal indicator

Question 24

Period 2 oxides?

Answer 24

Na2O = Yellow flame
MgO = BWL / white powder
AL2O3
SiO2
P4O10 = BWL 
SO2/SO3 = Blue flame

Question 25

Why are aqueous period 2 oxides alkaline?

Answer 25

O2- + H20 –> 2OH-

• NaOH ( pH 12-13)
• Mg(OH)2 ( pH 9-10)

Question 26

Why does magnesium hydroxide have a lower ph than sodium hydroxide?

Answer 26

It isn’t as soluble so only partially dissociates

Question 27

Why is silicon oxide acidic?

Answer 27

it reacts with bases

Question 28

Water added to P4O10 or Sulfur?

Answer 28

P4O10 + water –> H3PO4
SO2 + water –> H2SO3
SO3 + water –> H2SO4

Question 29

What is aluminium?

Answer 29

Amphoteric (aluminium oxide reacts with acids and bases)

Question 30

SiO2 + alkalis?

Answer 30

Ca(OH)2 + SiO2 –> CaSiO3 + water

Na2O + SiO2 –> Na2SiO3

Question 31

Magnesium with water?

Answer 31

Mg + H2O (l) –> Mg(OH)2 + H2

Mg + H2) (g) –> MgO + H2

Question 32

Displacement with group 7?

Answer 32

KCl KBr KI
Cl2 X Br2 I2
Br2 X X I2
I2 X X X