Chemical Changes

Question 1

Oxidation

Answer 1

oxygen reacts with a substance to make a new compound

Question 2

Reactions of metals with water

Answer 2

metal + water –> metal hydroxide + hydrogen`

Question 3

Please
Send
Charlie's
Monkeys
And
Charlie's
Zebra
In
Tiny
Lead
Handled
Cages
Securely
Guarded
Please

Answer 3

Potassium, Sodium ,Calcium , Magnesium, Aluminium, Carbon ,Zinc , Iron ,Tin , Lead , Hydrogen , Copper ,Silver, Gold

Question 4

OILRIG

Answer 4

Oxidation Is Loss of electrons

Reduction is Gain of electrons

Question 5

Magnesium Oxide

Answer 5

white

Question 6

Copper Oxide

Answer 6

green

Question 7

Iron hydroxide

Answer 7

rust

Question 8

metal + acid =

Answer 8

salt + hydrogen

Question 9

metal carbonate + acid

Answer 9

salt + carbon dioxide + water

Question 10

metal alkali + acid

Answer 10

salt + water

Question 11

If something is acidic it contains what

Answer 11

hydrogen ions

Question 12

If something is alkaline it contains what

Answer 12

hydroxide ions

Question 13

What happens when acids are added to aqueous solutions

Answer 13

they ionise to produce hydrogen ions

Question 14

Strong acids

Answer 14

completely dissociate

Question 15

Weak acids

Answer 15

partly ionise

Question 16

Strength

Answer 16

measure of hydrogen ions

Question 17

Concentration

Answer 17

grams or moles per dm³

Question 18

Neutralisation Reaction

Answer 18

H+(aq) + OH-(aq) arrow H2O(l)

Question 19

Electrolysis

Answer 19

the process of decomposing a liquid ionic compound by passing a direct electrical current through it

Question 20

PANIC

Answer 20

Positive Anode Negative is Cathode

Question 21

Cation

Answer 21

positive ion

Question 22

Anion

Answer 22

negative ion

Question 23

Cathode Half Equations

Answer 23

Na + e- arrow Na

Question 24

Anode Half Equations

Answer 24

2Cl- arrow Cl2 + 2e-

Question 25

Why is it electrolysis expensive ?

Answer 25

high temperature is needed to break ionic bonds as a lot of energy is needed to break bonds

Question 26

M.P of aluminium ore (brauxite)

Answer 26

2050 degrees celsius

Question 27

Electrolysis of Alumium

Answer 27

the ore is dissolved in a compound called cryolite which lowers the m.p to 700 degrees Celsius and makes it cheaper.

Question 28

Solution

Answer 28

it is dissolved in water

Question 29

Hydroxide ions….(when oxygen forms at the electrode)

4OH- arrow H20 + 02 + 4e-

Answer 29

give up electrons more easily than Sulfate ions so oxygen forms.

Question 30

Molten

Answer 30

means it has been melted

Question 31

Aqueous

Answer 31

it has been dissolved in water

Question 32

Electrolysis is Aqueous Solutions Cathode

Answer 32

is the metal electrolyte more reactive than hydrogen

if yes = then hydrogen gas is produced
if no = then that metal is produced (copper ,gold , silver or platinum)

Question 33

Electrolysis is Aqueous Solutions Anode

Answer 33

is the negative ion in the electrolyte a halide ?

if yes = then that halogen gas is produced at the ANODE !

if no = then oxygen gas is produced

Question 34

Neutralising an alkali with an acid, titration could be used to calculate the concentration of the alkali

Answer 34

The concentration of the acid to be added

The volume of the alkali

Question 35

If both the acid and alkali are strong, suitable indicators would be:

Answer 35

Methyl orange (yellow in alkali → red in acid).
Phenolphthalein (pink in alkali → colourless in acid).

Question 36

Titration

Answer 36

1) Use the pipette and pipette filler to add a measured volume of sodium hydroxide solution to a clean conical flask.
2) Add a few drops of indicator and put the conical flask on a white tile.
3) Fill the burette with hydrochloric acid and note the starting volume.
4) Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
5) Stop adding the acid when the end-point is reached (when the indicator first permanently changes colour). 6) Note the final volume reading.
Repeat steps 1 to 5 until concordant titres are obtained. More accurate results are obtained if acid is added drop by drop near to the end-point.