Ch6 Types of reaction- precipitation, acid-base and redox

Question 1

precipitation reaction

Answer 1

cation and anion in solution combine to form an insoluble substance that precipitates out as a solid

Question 2

Anions

Answer 2

negative ions

Question 3

Cations

Answer 3

positive ions

Question 4

Redox reaction

Answer 4

Electrons are transferred from one substance to another

Question 5

Rules of oxidation numbers

Answer 5

1. all elements in natural state have oxidation number 0
2. oxidation numbers of atoms of any molecule add up to 0
3. oxidation number of components of any ion add up to charge on that ion

Question 6

Oxidation order of priority

Answer 6

1. Group 1,2 and 3 oxi no’s are always +1,+2 and +3 respectively
2. oxidation number of fluorine is always -1
3. oxidation number of hydrogen is normally +1
4. oxidation number of oxygen is normally -2
5. the oxidation number of chlorine is usually -1

Question 7

oxidising agent

Answer 7

encourages oxidation- substance that receives electrons readily

e.g. group 7

Question 8

reducing agent

Answer 8

encourages reduction- substance that donates electrons readily

e.g. group 2

Question 9

Trends for redox down group 2

Answer 9

More likely to lose electron
More easily oxidised
Becomes better reducing agent

Question 10

Trends for redox down group 7

Answer 10

Less likely to gain an electron
Less easily reduced
Becomes worse oxidising agent

Question 11

Acids pH

Answer 11

below 7

Question 12

Alkali pH

Answer 12

above 7

Question 13

Strong Acid

Answer 13

proton donor that completely dissociates its ions in water

Question 14

Weak acid

Answer 14

proton donor that only partially dissociates into its ions in water

Question 15

Strong acid examples

Answer 15

Hydrochloric acid HCl
Sulfuric acid H2SO4
Nitric acid HNO3

Question 16

Weak acid examples

Answer 16

Phosphoric acid H3PO4
Ethanoic acid CH3COOH

Question 17

Base

Answer 17

reacts with H+ ion released by acid
proton acceptor

Question 18

Alkali

Answer 18

soluble base- can accept protons in solution
release OH- ions in water

Question 19

Alkali examples

Answer 19

Sodium hydroxide NaOH
Potassium hydroxide KOH
Ammonia NH3

Question 20

Role of water in acidity and alkalinity

Answer 20

water must be present for substances to act as acids and alkalis

Release H+ ions/ OH- ions when dissolved in water

Question 21

Salt

Answer 21

When an acid has one or more of it’s hydrogen ions replaced by either a metal ion or ammonium ion

Question 22

Different neutralisation reactions

Answer 22

• acid + alkali
• acid + base
• acid + carbonate
• acid + metal

Question 23

Sequence of ion tests

Answer 23

Carbonate
Sulfate
Halide

Question 24

Test for carbonate ions

Answer 24

Add dilute HCl
If effervescence is given off, CO2 gas has been given off and carbonate is present

Question 25

Test for Sulfate ions

Answer 25

Add solution of barium chloride(BaCl2)
If white precipitate is formed(BaSO4) a sulfate is present

Question 26

Test for ammonium ions

Answer 26

Warm NH4+ with dilute sodium hydroxide
NH3(g) is produced turning moist red litmus blue

Question 27

Reaction of acid + base/alkali

Answer 27

Produces salt and water

Question 28

Reaction of acid + carbonate

Answer 28

Produces salt, water and carbon dioxide

Question 29

Reaction of acid + metal

Answer 29

Produces salt and hydrogen gas

Question 30

Disproportionation reaction

Answer 30

When the same element both increases and decreases its oxidation numbers so that the element is simultaneously oxidised and reduced