Chemical Changes

Question 1

What is oxidation?

Answer 1

When a substance gains oxygen

Question 2

What is reduction?

Answer 2

When a substance loses oxygen

Question 3

What is a displacement reaction?

Answer 3

A reaction where a more reactive metal displaces a less reactive metal from a compound

Question 4

How are unreactive metals found on Earth?

Answer 4

In their natural state

Question 5

How can metals less reactive than carbon be extracted?

Answer 5

Reduction with carbon. Carbon displaces the metal in a metal oxide

Question 6

How are metals more reactive than carbon extracted?

Answer 6

By electrolysis

Question 7

How is oxidation defined in terms of electron transfer?

Answer 7

loss of electrons

Question 8

How is reduction defined in terms of electron transfer?

Answer 8

gain of electrons

Question 9

What is the general equation for a reaction between metals and
acids?

Answer 9

Metal + acid → salt + hydrogen

Question 10

What is a redox reaction?

Answer 10

Redox reactions are reactions where both oxidation and reduction are taking place

Question 11

Which metals in the reactivity series will react with acid?

Answer 11

Those above hydrogen

Question 12

How is a soluble salt formed?

Answer 12

1) React the excess acid with some insoluble chemical (e.g. metal oxide)
2) Filter off the leftovers
3) Crystallise the product

Question 13

What are bases?

Answer 13

Bases are compounds that neutralize acids

Question 14

What are alkailis?

Answer 14

alkalis are soluble bases - produce hydroxide ions in aqueous solutions

Question 15

What are acids?

Answer 15

acids produce hydrogen ions in aqueous solutions

Question 16

What do acids produce in aqueous solutions?

Answer 16

Hydrogen ions (H+)

Question 17

What do alkalis produce in aqueous solutions?

Answer 17

Hydroxide ions (OH-)

Question 18

What is the pH scale?

Answer 18

The measure of acidity/alkalinity of a solution

Question 19

What is a strong acid?

Answer 19

A strong acid is completely ionized in aqueous solution

Question 20

What is a weak acid?

Answer 20

A weak acid is only partially ionized in aqueous solution

Question 21

What happens to pH as the concentration of H+ increases?

Answer 21

The pH decreases

Question 22

What is a concentrated acid?

Answer 22

Concentrated acid has lots of moles of acid per unit

Question 23

What is a dilute acid?

Answer 23

Dilute acid has a few moles of acid per unit

Question 24

What is electrolysis?

Answer 24

The passing of an electric current through ionic substances that are molten or in solution to break them down into elements

Question 25

What is an electrolyte?

Answer 25

The liquid/solution that conducts electricity

Question 26

What is a cathode?

Answer 26

The cathode is the negative electrode

Question 27

What is an anode?

Answer 27

The anode is the positive electrode

Question 28

What occurs at the cathode and what occurs at the anode during electrolysis?

Answer 28

Reduction occurs at the cathode Oxidation occurs at the anode

Question 29

Why is the manufacturing of aluminum expensive?

Answer 29

Lots of energy is needed to produce the current in electrolysis which makes this process expensive.

Question 30

What are the half equations in the extraction of aluminum?

Answer 30

Al^3+ + 3 e^− → Al (cathode) 2O^2− → O2 + 4e− (anode)

Question 31

Why is cryolite used in the electrolysis of aluminum?

Answer 31

It lowers the melting point of aluminum oxide, reducing energy costs

Question 32

What are the different reactions with acids?

Answer 32

MASH BAWS CAWSC

Question 33

What is MASH?

Answer 33

metal + acid → salt + hyrdrogen

Question 34

What is BAWS?

Answer 34

base + acid → + water + salt

Question 35

What is CAWSC

Answer 35

carbonate + acid → water + salt + CO2