Chapter 8 Reactivity Trends

Question 1

Group 2 redox reactions with oxygen

Answer 1

• react with oxygen to form a metal oxide with the general formula MO M2+ and O2-

Question 2

Group 2 redox reactions with water

Answer 2

• react with water to form an alkaline hydroxide with the general formula M(OH)2 and Hydrogen gas
• reactivity increases down the group

Question 3

Redox reactions with dilute acids

Answer 3

• metal + acid > salt + hydrogen

- reactivity increases down the group

Question 4

Trends of group 2

Answer 4

-ionisation energy decreases down the group
- hydroxide solubility increases, ph increases, alkalinity increases down the group
-

Question 5

Group 2 oxides

Answer 5

• Reacts with water to form metal hydroxides

Question 6

Uses of group 2 compounds

Answer 6

• calcium hydroxide is added to fields as lime by farmers to increase the pH of acidic soils forming neutral water
• used as antacids for treating acid indigestion

Question 7

Reducing agent

Answer 7

A reagent that reduces (adds electron to) another species.

Group 2 elements

Question 8

oxidising agent

Answer 8

A reagent that oxidises (takes electrons from) another species.

Question 9

disproportionation

Answer 9

A redox reaction in which the same element is both oxidised and reduced.

Question 10

Reaction of chlorine with water

Answer 10

Cl2 (aq) + H2O(l) > HClO(aq) + HCl(aq)

Question 11

Reaction of chlorine with cold, dilute aqueous sodium hydroxide

Answer 11

Cl2(aq) + 2NaOH(aq) > NaClO(aq) +NaCl(aq) + H2O(l)

Question 12

Benefits and risks of chlorine use

Answer 12

• kills bacteria to make water safe to drink
  ~ Toxic gas- respiratory irritant
  ~ react with organic hydrocarbons to form chlorinated hydrocarbon- carcinogenic

Question 13

Carbonate test

Answer 13

1. Add dilute nitric acid to solid/solution to be tested
2. Bubble any gas produced through lime water
3. CO2 reacts to form a fine white
   precipitate of calcium carbonate
   CO2 + Ca(OH)2 > CaCO3 + H2O

Question 14

Sulfate test

Answer 14

1. Add barium nitrate to solution
2. BaSO4 a white precipitate is formed if sulphates are present
   Ba2+ + SO42- >BaSO4

Question 15

Halide test

Answer 15

1. Add aqueous silver nitrate to an aqueous solution of a halide
2. Silver halides form different coloured precipitates
3. Cl- white Br-cream I- yellow
4. Add aqueous ammonia to test the solubility of the precipitate
5. Cl- soluble in dilute NH3 Br- soluble in conc. NH3 I- insoluble in conc. NH3

Question 16

Sequence of ion tests

Answer 16

1. Carbonate
2. Sulfate
3. Halides