Chemical Changes(electrolysis)

Question 1

What ions make up an acid

Answer 1

H+

Question 2

What ions make an alkali

Answer 2

OH-

Question 3

PH ranges for alkali and acid

Answer 3

Acid less than 7
Strongest 1

Neutral - 7

Alkali- greater then 7
PH14 the strongest

Question 5

What can be used to measure PH

Answer 5

Universal indicator

PH probe

Question 6

What colour is methyll orange in an acid and alkali

Answer 6

Acid - red

Alkali - yellow

Question 7

Problem with using a universal indicator to test the PH

Answer 7

It doesn’t provide an exact PH value

People may disagree what colour the solution matches on the PH chart

Question 8

What colour is blue litmus paper in acid and alkali

Answer 8

Acid - stays red
Alkali - stays blue

Question 9

What does a low PH of acid mean

Answer 9

High concentration of H+ ions

Question 10

What happens when the PH increases by 1

Answer 10

The hydrogen ion concentration increases by 10

Question 11

What is a neutralisation reaction

Answer 11

Reaction between an acid and a base

H+ ions react with OH- ions to create water

Question 12

Concentrated vs dilute

Answer 12

Concentrated acids have more moles of acid per unit

Concentration of an acid isn’t the same as strength

Strength is if the acid has completely dissociated in water or not

Question 13

What is a base

Answer 13

Any substance which reacts with an acid to form salt and water only

Question 14

Test for hydrogen

Answer 14

Insert a lit splint in a test tube of gas

If squeaky pop is heard hydrogen is present

Question 15

Test for carbon dioxide

Answer 15

Bubble the gas through limewater

Limewater turns cloudy and milky

Question 16

What is an electrolyte

Answer 16

An ionic compound in its molten or aqueous state

Aqueous- dissolved in water

Question 17

Why can electrolytes carry a charge

Answer 17

An ionic compound in molten or aqueous state has mobile irons which can carry charge

Question 18

What is electrolysis

Answer 18

The splitting of ionic compound using electricity

Question 19

What are the electrodes and which ions go to which

Answer 19

Anode - positive and attract anions

Cathode - negative and attract cations

Question 20

What happens at the anode during electrolysis

Answer 20

The anions lose electrons to form there elements

Question 21

What happens at the cathode during electrolysis

Answer 21

Cations gain electrons to form there element

Question 22

What process happens at each electrode

Answer 22

Anode - oxidation

Cathode - reduction

Question 23

What is formed at each electrode

Answer 23

Cathode - metal or hydrogen
Anode - non metal

Question 24

How do you know is metal or hydrogen will form at the cathode(negative electrode)

Answer 24

If hydrogen is above the metal in reactivity series the metal will form

If the metal is more reactive then hydrogen then hydrogen will form

Question 25

What is formed at each electrode during electrolysis of copper chloride

Answer 25

Positive(anode) : chlorine Negative (cathode) :copper

Question 26

Half equations of copper chloride

Answer 26

Anode - Cl- — cl2 +2e- Cathode - Cu2+ + 2e- — cu

Question 27

What does oxidation mean

Answer 27

Loss of electrons

Question 28

What does reduction mean

Answer 28

Gain of electrons

Question 29

How electrolysis of copper surface can be used to purify copper

Answer 29

Place 2 copper electrodes into copper sulfate solution The anode should be impure and cathode pure Connect to a power supply The copper in the impure anode is pulled towards the cathode to form pure copper Impurities form as sludge below the anode Cu2+ ions remain in the solution