Topic 3 - Chemical Changes Flashcards Preview

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Flashcards in Topic 3 - Chemical Changes Deck (23):
1

Alkali

Soluble base

2

Base

Reacts with acid to form a salt + water

3

Litmus paper

Red - acidic
Purple - neutral
Blue - Alkali

4

Methyl Orange

Red - acidic
Yellow - neutral + alkali

5

Phenolphthalein

Colourless - acidic or neutral
Pink - alkali

6

Disassociation

When in water they disassociate.

7

Weak acid

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

8

Acid strength PH

Tells the proportion of disassociation.

9

Acid concentration

Measures how much acid in one dm^3

10

By increasing the concentration by a factor of 10.

The PH rises by 1.

11

Make insoluble salt

Precipitation reaction

12

Precipitation reaction

2 soluble salts picked and reacted

13

Collect insoluble salt.

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.

14

Make a soluble salt

Acid + insoluble base (BASHO)

Acid + alkali (soluble, BASHO)

15

Soluble salt by acid and insoluble base

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.

16

Soluble salt by acid + alkali (soluble base)

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.

17

Cathode (negative)

Positive ions move to and are reduced (gain)

18

Anode (positive)

Negative ions are attracted and oxidised (loss)

19

Electrodes must be

Inert (graphite or platinum)

20

Cathode in aqueous

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

21

Anode in aqueous

If HALIDE PRESENT, HALIDE GAS forms
If none OXYGEN GAS is formed

22

Electrolysis of copper sulfate

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

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

23

Inert electrodes

Cathode mass increases, reduction (Cu forms)

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