acids, bases, salts

Question 1

phenolphthalein in acid

Answer 1

colourless

Question 2

phenolphthalein in alkali

Answer 2

pink

Question 3

methyl orange in acid

Answer 3

red

Question 4

methyl orange in alkali

Answer 4

yellow

Question 5

define an acid in terms of:

• ions in aqueous solution

- protons

Answer 5

• dissociates to form H+ ions in an aqueous solution

- proton donor

Question 6

define an alkali in terms of:

• ions in aqueous solution

- protons

Answer 6

• dissociates to form OH- ions in an aqueous solution

- proton acceptor

Question 7

base + acid

Answer 7

salt + water

Question 8

metal carbonate + acid

Answer 8

salt + water + carbon dioxide

Question 9

metal + acid

Answer 9

salt + hydrogen

Question 10

give three examples of compounds that can act as bases

Answer 10

• ammonia
• metal oxides
• metal hydroxides

Question 11

all compounds containing ??? will always be soluble

Answer 11

sodium, potassium, ammonium

Question 12

solubility of nitrates

Answer 12

all soluble

Question 13

solubility of chlorides

Answer 13

all soluble except silver and lead(II)

Question 14

solubility of sulfates

Answer 14

all soluble except barium, calcium and lead(II)

Question 15

solubility of carbonates

Answer 15

all insoluble except sodium, potassium, ammonium

Question 16

solubility of hydroxides

Answer 16

all insoluble except sodium, potassium, ammonium and calcium (ss)

Question 17

describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an insoluble reactant

Answer 17

insoluble base + acid (to make all soluble salts except Na,K,NH4)

1. measure acid into beaker
2. warm acid to speed up reaction
3. add solid until no more will dissolve
4. filter to remove excess solid
5. filtrate contains solution of soluble salt
6. heat solution until saturation point
7. leave overnight to form crystals
8. dry in a warm oven.

Question 18

describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an acid and alkali

Answer 18

soluble base + acid (to make all soluble salts with Na, K, NH4)

1. fill burette with acid
2. pipette base into conical flask
3. add indicator
4. add acid gradually until colour change
5. record volume added
6. repeat until 3+ concordant results
7. repeat using average volume of acid but no indicator
8. heat until saturation point
9. leave overnight to form crystals
10. dry in a warm oven

Question 19

describe an experiment to prepare a pure, dry sample of an insoluble salt, starting from two soluble reactants

Answer 19

soluble salt + soluble salt -> insoluble salt + soluble salt

1. mix 2 solutions
2. filter to isolate solid
3. wash with distilled water
4. dry in a warm oven