Topic 3: Electrolysis, Chemical changes

Question 1

Magnesium + oxygen ~ magnesium oxide

Answer 1

2Mg + O2 ~ 2MgO

Question 2

Oxidation?

Answer 2

This is when oxygen is gained by a compound during a reaction

Question 3

What happens to electrons in oxidation?

Answer 3

In oxidation you loose electrons

Question 4

What happens to electrons in reduction?

Answer 4

In reduction you gain electrons

Question 5

What charge is the anode?

Answer 5

Positive +

Question 6

What charge is the cathode?

Answer 6

Negative -

Question 7

What charge is the anions?

Answer 7

Negative -

Question 8

What charge is the cations?

Answer 8

Positive +

Question 9

What does the anode attract?

Answer 9

Anions

Question 10

What does the cathode attract?

Answer 10

Cations

Question 11

What happens to metals in electrolysis?

Answer 11

They have a positive charge so they go to the negative electrode (cathode) if they are more reactive then hydrogen (group 1, 2 and aluminium)

Question 12

What happens to non-metals in electrolysis?

Answer 12

They have a negative charge so they attract to the positive electrode (anode)

Question 13

Differences in acids and alkalis in aqueous solutions?

Answer 13

Acids produce H+ ions

Alkalis produce OH- ions

Question 14

PH scale?

Answer 14

7 is neutral
Below 7 is acidic
Above seven is alkali

Question 15

Indicator phenolphthalein?

Answer 15

Alkaline= pink 
Acidic= colourless

Question 16

Methyl orange indicator?

Answer 16

Alkaline= yellow
Acidic= red

Question 17

Litmus solution indicator?

Answer 17

Alkaline= blue
Acidic= red

Question 18

Litmus paper indicator?

Answer 18

Blue paper goes red when acidic, stays blue when alkaline

Red litmus paper stays red in acidic, goes blue when alkaline

Question 19

What happened as PH decreases?

Answer 19

If PH decreases by one unit, H+ increases by factor of 10

Question 20

Test for hydrogen?

Answer 20

Burning splint held at end of test guide of gas. Makes a ‘squeaky pop’ sound of hydrogen is present

Question 21

Test for carbon dioxide?

Answer 21

If you bubble the gas in limewater (calcium hydroxide solution) and it will turn milky or cloudy

Question 22

Soluble salts?

Answer 22

Sodium, potassium, ammonium, nitrates, chlorides(all except silver and lead), sulfates(all except lead barium and calcium)

Question 23

Insoluble salts?

Answer 23

Carbonates(all except sodium, potassium, ammonium), hydroxides(all except sodium, potassium, ammonium)

Question 24

Mixtures being separated?

Answer 24

Mixtures are easily separated, unlike compounds because there’s no chemical bond between the different parts. The different parts of either compounds or elements can be separated by physical methods: filtration, crystallisation or distillation, or chromatography. Different parts within a mixture will still have their separate properties

Question 25

Chromatography?

Answer 25

Used to separate mixtures, eg.dyes in an ink. Draw a line near the bottom of filter paper in pencil.Add a spot of the ink to the line and place bottom of beaker in solvent.Most dissolve well in water but some need ethanol.Make sure ink isn’t touching the solvent as the ink shouldn’t dissolve into the solvent .Place a lid to stop solvent evaporating.Solvent seeps up paper, carrying the ink with it .Each dye will move at a different rate and therefore separate, each dye makes a spot. Insoluble inks will stay at the baseline. When the solvent has nearly reached the top of the paper take it out. End results is a pattern of spots- chromatogram

Question 26

Filtration?

Answer 26

Separates insoluble solids from liquids. It can also be used in purification. Filter paper is folded into a cone and solid is left in the filter paper because the liquid will seep through the filter paper and into the beaker

Question 27

Evaporation?

Answer 27

Separate a soluble solid/salt from a solution. Pour solution into an evaporating dish. Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually, crystals will form. Keep heating until all you have left are dry crystals

Question 28

Crystallisation?

Answer 28

For separating a salt that decomposes(breaks down when heated) from a liquid. Pour the solution into an evaporating dish and gently heat the solution. Some of the liquid will evaporate and the solution will get more concentrated. Once some of the solvent has evaporated, or you see crystals start to form remove the dish from the heat and leave to cool.
Salt should start to form crystals. Leave them in a warm place to dry.