Topic 3 - Chemical Changes

Question 1

Alkali

Answer 1

Soluble base

Question 2

Base

Answer 2

Reacts with acid to form a salt + water

Question 3

Litmus paper

Answer 3

Red - acidic
Purple - neutral
Blue - Alkali

Question 4

Methyl Orange

Answer 4

Red - acidic

Yellow - neutral + alkali

Question 5

Phenolphthalein

Answer 5

Colourless - acidic or neutral

Pink - alkali

Question 6

Disassociation

Answer 6

When in water they disassociate.

Question 7

Weak acid

Answer 7

Don’t fully disassociate. In a reversible reaction at equilibrium.

Question 8

Acid strength PH

Answer 8

Tells the proportion of disassociation.

Question 9

Acid concentration

Answer 9

Measures how much acid in one dm^3

Question 10

By increasing the concentration by a factor of 10.

Answer 10

The PH rises by 1.

Question 11

Make insoluble salt

Answer 11

Precipitation reaction

Question 12

Precipitation reaction

Answer 12

2 soluble salts picked and reacted

Question 13

Collect insoluble salt.

Answer 13

Dissolve 2 soluble salts. Add them together. Allow precipitate to form. FILTER. Swill out contents to collect all precipitate. Rinse all insoluble salt with water to remove soluble salts. Collect and dry.

Question 14

Make a soluble salt

Answer 14

Acid + insoluble base (BASHO)

Acid + alkali (soluble, BASHO)

Question 15

Soluble salt by acid and insoluble base

Answer 15

Choose the correct reactants by the ions you need.

1. Heat acid to increase rate of reaction
2. Add insoluble base in excess (ensuring there’s no leftover acid in product)
3. Filter excess solid to acquire a solution (salt + water)
4. Evaporate off water and allow it to crystallise.

Question 16

Soluble salt by acid + alkali (soluble base)

Answer 16

Titration - as there’s no visible sign that the reaction has finished.

Using a burette slowly add alkali to the acid until the chosen indicator changes colour.

Collect solution and evaporate.

Question 17

Cathode (negative)

Answer 17

Positive ions move to and are reduced (gain)

Question 18

Anode (positive)

Answer 18

Negative ions are attracted and oxidised (loss)

Question 19

Electrodes must be

Answer 19

Inert (graphite or platinum)

Question 20

Cathode in aqueous

Answer 20

If the metal is MORE reactive than hydrogen, HYDROGEN GAS IS FORMED

Question 21

Anode in aqueous

Answer 21

If HALIDE PRESENT, HALIDE GAS forms

If none OXYGEN GAS is formed

Question 22

Electrolysis of copper sulfate

Answer 22

Produces oxygen, copper is less reactive so copper forms.
Cu 2+ + 2e- -> Cu

4OH- -> O2 + 4H2O + 4 e-

Question 23

Inert electrodes

Answer 23

Cathode mass increases, reduction (Cu forms)

anode mass decreases, oxidation (Cu2+ forms), impurities sink