3.4 - Acids, bases and salts

Question 1

Acid

Answer 1

H+ donor
Acids dissolve and then donate H+ ions into the water, causing a solution to have a pH less than 7 - acidic

Question 2

Alkali

Answer 2

OH- donor
Alkalis dissolve and then donate OH- ions into the water, causing a solution to have a pH more than 7 - alkaline

Question 3

Base

Answer 3

H+ acceptor
Bases dissolve and then accept H+ ions from the H2O molecules, but when an H2O molecule loses an H+ ion, what’s leftover is an OH- ion - this causes the solution to have a pH more than 7 - alkaline

Question 4

Difference between acidic/alkaline and acid/alkali

Answer 4

Acid or alkali refer to substances in terms of ions
Acidic or alkaline describes a solution in terms of pH

Question 5

Common acids

Answer 5

• Hydrochloric acid - HCl
• Nitric acid - HNO3
• Sulphuric acid - H2SO4
• Phosphoric acid - H3PO4
• Carbonic acid - H2CO3

Question 6

Common alkalis

Answer 6

• Sodium hydroxide - NaOH
• Potassium hydroxide - KOH
• Ammonium hydroxide - NH4OH
• (all soluble metal hydroxides)

Question 7

Common bases

Answer 7

• Ammonia - NH3
• (all metal oxides)
• (all metal hydroxides)

Question 8

Polyatomic ion definition

Answer 8

An ion that contains more than one atom

Question 9

Acid and base reaction

Answer 9

Acid + base —> salt + water

Question 10

Reaction between zinc oxide and sulphuric acid

Answer 10

Zinc oxide + sulphuric acid —> zinc sulphate + water

Question 11

Observations in an acid and base reaction

Answer 11

The base disappears as it is used up in the reaction
If the salt is soluble, it dissolves in the water to form a salt solution

Question 12

Ammonia and acid reaction

Answer 12

Ammonia + acid —> ammonium salt

Question 13

Reaction between ammonia and hydrochloric acid

Answer 13

Ammonia + hydrochloric acid —> ammonium chloride

Question 14

What are solubility rules used for

Answer 14

To determine if a salt is soluble in water or not

Question 15

Solubility rules - soluble

Answer 15

• all group 1 and ammonium salts
• all nitrates
• most halides (except silver and lead halides)
• most sulphates (except lead, barium and calcium sulphate)

Question 16

Solubility rules - insoluble

Answer 16

• silver halides, lead halides
• lead, barium and calcium sulphate
• oxides, hydroxides and carbonates

Question 17

Making soluble salts method

Answer 17

1. Heat the acid
2. Add the base
3. Filter excess base

Question 18

Making insoluble salts method

Answer 18

1. Filter out salt precipitate
2. Rinse with water
3. Pat dry with filter paper

Question 19

Crystallisation method

Answer 19

1. Heat salt solution
2. Allow solution to cool
3. Filter out crystals
4. Pat dry with filter paper

Question 20

Titration method

Answer 20

1. Perform titration to measure volume of acid and alkali that neutralise each other
2. Use phenolphthalein
3. Pink —> colourless
4. Swirl continuously

Question 21

Acid and carbonate reaction

Answer 21

Acid + carbonate —> salt + water + carbon dioxide

Question 22

Observations in an acid and carbonate reaction

Answer 22

Carbonate disappears as it is used up in the reaction
Fizzing as a gas (carbon dioxide) is produced
If the salt is soluble, it dissolves into the water to form a salt solution