2.1.4 Acids 2.1.5 Redox

Question 1

Name the common acids

Answer 1

HCl
H2SO4
HNO3
CH3COOH

Question 2

Name the common alkalis

Answer 2

NaOH
KOH
NH3

Question 3

What do acids do when dissolved in water

Answer 3

Release hydrogen ions as protons H+

Question 4

What do alkalis do when dissolved in water

Answer 4

Release hydroxide ions, OH-

Question 5

What is a strong acid

Answer 5

Completely dissociates/ionises in aqueous solution, releases all its hydrogen atoms into solution.

Question 6

Examples of strong acids

Answer 6

HCl
H2SO4
HNO3

Question 7

What is a weak acid

Answer 7

Partially dissociates/ionises in aqueous solution, only releases small proportion of available H atoms into solution as H+

Question 8

Examples of weak acids

Answer 8

CH3COOH

Question 9

Examples of bases

Answer 9

Metal oxides
Metal hydroxides
Metal carbonates
Ammonia

Question 10

What is a neutralisation reaction?

Answer 10

H+ and OH- react to form H20
Reaction between acid and base to form salts

Question 11

What does acid + metal oxide make

Answer 11

Salt + water

Question 12

What does metal hydroxide + acid make

Answer 12

Salt + water

Question 13

What does acid + alkali make

Answer 13

Salt + water

Question 14

What does acid + metal carbonate make

Answer 14

Salt + water + carbon dioxide

Question 15

What can titrations be used for

Answer 15

Finding concentration of a solution
Identification of unknown chemicals
Finding purity of a substance

Question 16

How to prepare a standard solution

Answer 16

Weigh solid accurately
Dissolve solid in beaker using distilled water, less than needed to fill volumetric flask
Transfer solution to volumetric flask
Rinse beaker into flask
Fill flask to graduation line, bottom of meniscus lines up with mark, view from eye level
Slowly invert flask to mix solution

Question 17

How to carry out an acid-base titration

Answer 17

Add measured volume of one solution to conical flask using a pipette
Add other solution to burette, record initial reading
Add a few drops of indicator to solution in the conical flask
Run solution in the burette into conical flask, swirl flask throughout.
Indicator changes colour at the end point of the titration.
Record final burette reading, work out titre.
Repeat titration accurately, adding solution drop wise as end point is approached.
Further titrations carried out until 2 accurate titres are concordant (within 0.10cm3)

Question 18

What is the oxidation number for elements

Answer 18

0

Question 19

What is the oxidation number for oxygen in compounds

Answer 19

-2

Question 20

What is the oxidation number for hydrogen in compounds

Answer 20

+1

Question 21

What is the oxidation number for fluorine in compounds

Answer 21

-1

Question 22

What is the oxidation number for ions

Answer 22

The same as the ionic charge

Question 23

What are the exceptions for the oxidation number rules in compounds

Answer 23

Hydrogen is -1 in metal hydrides
Oxygen is -1 in peroxides
Oxygen is +2 when bonded to fluorine

Question 24

What is the sum of oxidation numbers in a compound

Answer 24

The total charge

Question 25

Oxidation in terms of electron transfer

Answer 25

Loss of electrons

Question 26

Reduction in terms of electron transfer

Answer 26

Gain of electrons

Question 27

Oxidation in terms of oxidation number

Answer 27

Increase in oxidation number

Question 28

Reduction in terms of oxidation number

Answer 28

Decrease in oxidation number

Question 29

Redox reaction of zinc and dilute hydrochloric acid

Answer 29

Zn(s) + 2HCl (aq) -> ZnCl2(aq) + H2 (g) Zinc goes from 0 to +2, oxidation Hydrogen goes from 1+ to 0, reduction

Question 30

Redox reaction of aluminium with dilute sulfuric acid

Answer 30

2Al (s) + 3H2SO4 (aq) -> Al2(SO4)3 (aq) + 3H2 (g) Aluminium goes from 0 to +3, oxidation Hydrogen goes from +1 to 0, reduction