Chapter 11 Acids and Bases - Only Alkali

Question 1

What are alkali/bases

Answer 1

Substances that consist of one or more replaceable hydroxide (OH-) ions and are proton acceptors

Question 2

Difference between bases and alkali

Answer 2

Bases are generally insoluble oxides and hydroxides of metal

Alkali are metal soluble hydroxides (soluble bases)

Question 3

Properties of Alkali

Answer 3

Bitter in taste
Corrosive
Proton acceptors
OH- donors

Question 4

Differentiate between a strong and weak base
pH levels

Answer 4

Strong alkalis completely dissociate into ions in water producing lots of OH- ions
pH: 12-14

Weak alkalis partially dissociate into ions in water producing OH- ions
pH: 11-8

Question 5

Indicator colour changes
Litmus
Methyl Orange
Thymolphthalein
Phenolphthalein

what pH range are alkalis

Answer 5

Red litmus - Blue
Methyl Orange - Yellow
Thymolphthalein - Blue
Phenolphthalein - Pink/purple

pH: 8 (weak) - 14 (strong)

Question 6

Colour of universal indicator in alkalis

Answer 6

pH 8: Greenish-blue
pH 10: Blue
pH 12: Violet
pH 14: Dark purple

Question 7

Typical reactions of bases

Answer 7

Base + acid —> salt + water (+ CO2 when base is a metal carbonate)

Base + ammonium salt —> salt + ammonia gas + water

Question 8

describe the decomposition for a group 1 nitrate
eg sodium

Answer 8

2NaNO3 —> 2NaNo2 +O2

Question 9

describe the decomposition for a group 2 nitrate
eg magnesium

Answer 9

2Mg(NO3)2 –> 2MgO + 4NO2 + O2