C1- Chemical Changes

Question 1

What numbers are on the pH scale?

Answer 1

0-14

Question 2

Which pH numbers are acidic?

Answer 2

0-6

Question 3

Which pH numbers are neutral?

Answer 3

7

Question 4

Which pH numbers are alkaline?

Answer 4

8-14

Question 5

Give examples of a weak, medium and strong acid

Answer 5

Normal or acid rain
Lemon or vinegar
Car battery or stomach acid

Question 6

Give examples of a weak, medium and strong alkali

Answer 6

Washing up liquid
Pancreatic juice
Bleach

Question 7

Give an example of a substance with a pH of 7

Answer 7

Pure water

Question 8

What is an indicator?

Answer 8

A dye that changes colour depending on if it’s above or below a certain pH

Question 9

What is a wide range indicator?

Answer 9

Wide ranges have gradual colour changes over a broad range of pHs. For example universal indicators are the classic 0-14.

Question 10

What is a pH probe?

Answer 10

A pH probe attached to a pH meter measures it electronically. The probe is put into the solution you are measuring and the pH is given on a digital display as a numerical value.

Question 11

Acids and bases ____ eachother

Answer 11

Neutralise

Question 12

What do acids form in water?

Answer 12

H+ ions
Hydrogen ions
Protons

Question 13

What is a base?

Answer 13

Any substance that has a pH of more than 7, not just alkalis

Question 14

What do alkalis form in water?

Answer 14

OH- ions

Question 15

Acid + Base ->

Answer 15

Salt + Water

Question 16

H+ + OH- ->

Answer 16

H20

Question 17

What is the difference between how strong and weak acids act in water?

Answer 17

Strong acids fully ionise but weak acids only partially so only release some protons

Question 18

The pH of an acid or alkali is a measure of what?

Answer 18

The concentration of H+ ions in a soloution

Question 19

Factor H+ ion concentration changes by=

Answer 19

10^-x
X being the difference in pH (from 7 to 5 = -2)

Question 20

Metal oxides and metal hydroxides are b____

Answer 20

Bases

Question 21

Which type of bases are alkalis?

Answer 21

Water soluble compounds

Question 22

Acid + metal oxide/hydroxide ->

Answer 22

Salt + water

Question 23

What do acids and metal carbonated produce?

Answer 23

Carbon dioxide + Salt + Water

Question 24

Order of reactivity series from most to least

Answer 24

Potassium K
Sodium Na
Lithium Li
Calcium Ca
Magnesium Mg
Carbon C
Zinc Zn
Iron Fe
Hydrogen H
Copper Cu

Question 25

What 2 non metals are often included in the reactivity series?

Answer 25

Carbon and Hydrogen

Question 26

Acid + Metal ->

Answer 26

Salt + Hydrogen

Question 27

Metal + Water ->

Answer 27

Metal hydroxide + Hydrogen

Question 28

What is a reaction that separates a metal from its oxide called?

Answer 28

A reduction reaction

Question 29

What is a reduction reaction?

Answer 29

A reaction that separates a metal from its oxide

Question 30

Oxidation= ____ of Oxygen Reduction= ____ of Oxygen

Answer 30

Gain Loss

Question 31

Metals higher than carbon in the reactivity series have to be extracted from their ores using what?

Answer 31

Electrolysis which is expensive

Question 32

Metals below carbon in the reactivity series can be extracted from their ores using what?

Answer 32

Chemically using carbon

Question 33

Why can only less reactive metals be extracted from ores using carbon?

Answer 33

Because Carbon can only take Oxygen away from metals that are less reactive than itself

Question 34

What is a redox reaction?

Answer 34

A reaction where electrons are transferred

Question 35

Oxidation= __ of electrons Reduction= __ of electrons

Answer 35

Loss Gain

Question 36

What is the acronym to remember the meaning of oxidation and reduction?(electrons)

Answer 36

O xidation I s L oss R eduction I s G ain

Question 37

In what order does reduction and oxidation occur in a redox reaction?

Answer 37

At the same time REductionOXidation

Question 38

What type of reactions are displacement reactions?

Answer 38

Redox reactions

Question 39

What is the rule of a displacement reaction?

Answer 39

A more reactive metal will displace a less reactive metal from its compound

Question 40

In displacement reactions, it is always the metal ____ that gains electrons and is reduced. The metal ____ always loses electrons and is oxidised.

Answer 40

Ion Atom

Question 41

What happens to the metal ion and metal atom in a displacement reaction?

Answer 41

The ion is reduced and the atom is oxidised

Question 42

What do ionic equations show?

Answer 42

Only the reacting particles and products they formed

Question 43

What is electrolysis?

Answer 43

Using electricity to break down electrolytes to form elements

Question 44

What happens during electrolysis? (Detailed)

Answer 44

An electric current is passed through an electrolyte (a molten or dissolved ionic compound). The ions move towards the electrodes, where they react and the compound decomposes. The positive ions in the electrolyte will move to the cathode (-ve electrode) and gain electrons. They are reduced. The negative ions will move towards the anode (+ve electrode) and lose electrons. They are oxidised. This creates a flow of charge through the electrolyte as ions travel to the electrodes. As ions gain or lose electrons, they from the uncharged element and are discharged from the electrolyte.

Question 45

What is an electrolyte?

Answer 45

A liquid or a solution that can conduct electricity

Question 46

What is an electrode?

Answer 46

A solid that conducts electricity and is submerged in the electrolyte

Question 47

What does the electrolysis of molten ionic solids form?

Answer 47

Elements, they are reduced to their elements at the cathode and anode

Question 48

Why can't an ionic solid be electrolysed?

Answer 48

Because the ions are in fixed positions and can't move

Question 49

How can metals be extracted from their ores using electrolysis? (Aluminium)

Answer 49

1) Aluminium is extracted from the ore bauxite by electrolysis, which contains Aluminium oxide 2) Alumnium oxide has a very high melting point so it's mixed with cryolite to lower it 3) The molten mixture contains free ions so it conducts electricty 4) The positive Al^3+ ions are attracted to the cathode where they each pick up 3 electrons and turn into neutral aluminium atoms and sink to the bottom 5) The negative 0^2- ions go to the anode where they each lose 2 electrons. The neutral oxygen atoms will then combine to from 02 molecules

Question 50

What is in aqueous solutions during electrolysis as well as the ions from the ionic compound?

Answer 50

Hydrogen and hydroxide ions from the water

Question 51

What happens at the cathode in aqueous solutions if H+ and metal ions are present?

Answer 51

Hydrogen gas will be produced (if the hydrogen ions form an elemental metal more reactive than hydrogen). If less reactive than hydrogen, a solid layer of the pure metal will be produced instead.

Question 52

What happens at the anode in aqueous solutions if OH- and halide ions are present?

Answer 52

Molecules of Chlorine, Bromine or Iodine will be formed

Question 53

What happens at the anode in aqueous solutions if OH- ions are present but there are no halide ions?

Answer 53

The OH- ions are discharged, and oxygen will be formed

Question 54

What is the symbol for Hydrogen ions?

Answer 54

H+

Question 55

What is the symbol for Hydroxide ions?

Answer 55

OH-

Question 56

What are the symbols of Halide ions

Answer 56

Cl- Ir- Br-

Question 57

What do half equations show?

Answer 57

The reactions at the electrodes

Question 58

What should you remember when combining half equations?

Answer 58

The number of electrons needs to be the same for each half equation