periodicity + reactivity

Question 1

carbonate test

Answer 1

react with acid to form CO2 gas - add nitric acid and bubble gas through limewater

Question 2

sulfate test

Answer 2

barium sulfate = insoluble

barium chloride/nitrate added - white ppt = positive

Question 3

which substance should you use in the sulphate test if you want to do the halide test after it?

Answer 3

barium nitrate

Question 4

basis for halide test

Answer 4

silver halides are insoluble

Question 5

halide test

Answer 5

• add silver nitrate to aqueous halide solution
• ppt = positive
• add aqueous ammonia to test solubility to tell colours apart

Question 6

colour of chloride ppt

Answer 6

white

Question 7

solubility of chloride ppt in NH3

Answer 7

soluble in DILUTE

Question 8

colour of bromide ppt

Answer 8

cream

Question 9

colour of iodide ppt

Answer 9

yellow

Question 10

solubility of bromide ppt in NH3

Answer 10

soluble in CONCENTRATED

Question 11

solubility of iodide ppt in NH3

Answer 11

insoluble in CONCENTRATED

Question 12

sequence of qualitative analysis tests

Answer 12

1) Carbonate
2) Sulfate
3) Halide

Question 13

test for ammonium ion

Answer 13

• NaOH added to solution
• ammonia gas produced (v soluble In water)
• mixture warmed and gas released
• test pH with moist pH paper - turn BLUE

Question 14

can ammonium nitrate conduct electricity?

Answer 14

yes

Question 15

benefits of using chlorine in water purification

Answer 15

• kills bateria

Question 16

disadvantages of using chlorine in water purification (3)

Answer 16

• chlorine is toxic
• is respiratory irritant
• can react with hydrocarbons forming chlorinated hydrocarbons - cause cancer

Question 17

why do halogen boiling points increase down the group [3]

Answer 17

• London forces (dipole-dipole interactions increase)
• because number of electrons increase
• therefore more energy to break intermolecular forces

Question 18

why is it important that a colorimeter is calibrated before use? how would you calibrate it [3]

Answer 18

• to provide reference values
• record values given by colorimeter for known concentrations
• plot graph so unknown concentrations can be worked out from a given reading from colorimeter

Question 19

melting point trend across p 2+3

– why?

Answer 19

increase between 1 and 4
decreases 4-5
low from 5-0

– because change from giant to simple molecular structures

Question 20

group 2 elements act as

Answer 20

REDUCING AGENTS

Question 21

solubility of group 2 oxides down the group

- pH?

Answer 21

increases,

increases - alkalinity increases

Question 22

uses of group 2 compounds as bases

Answer 22

• Ca(OH)2 added to field to raise soil pH

- antacids

Question 23

boiling point trends down halogens

- why?

Answer 23

INCREASES

- more electrons, more London forces, more energy required to break bonds

Question 24

benefits of chlorine in water treatment (1)

Answer 24

kills bacteria

Question 25

disadvantages of chlorine in water treatment (3)

Answer 25

• toxic gas
• react w organic haloalkanes to produce chlorinated hydrocarbons - carcinogens
• respiratory irritant

Question 26

halide test

Answer 26

+ aq. silver nitrate

= 3 coloured ppts