Unit 8 ( Redox Reactions )

Question 1

what is oxidation

Answer 1

oxidation is a process in which a substance loses electrons, gains oxygen or loses hydrogen

Question 2

what is reduction

Answer 2

reduction is a process in which a substance gains electrons, loses oxygen or gains hydrogen

Question 3

alkanes chemical formula

Answer 3

CnH2n+2

Question 4

can oxidation reactions be usefull ?

Answer 4

redox reactions involve both oxidation and reduction. The cibustion of alkanes is a redox reaction.

Question 5

complete vs incomplete combustion (oxygen supply and color of flame shiuld be mentioned) (

Answer 5

A blue flame indicates that complete combustion is occurring. sufficient oxygen is being supplied and the flame burns cleanly. The yellow flame indicates that incomplete combustion is occurring. Insufficient oxygen is being supplied and teh flame does not burn cleanly.

Question 6

ratio o methane to oxygen in complete and two ty[es of incomplete combsution

Answer 6

complete combustion producing carbon dioxide and water : 1:2

incomplete combustion producing carbon monoxide and water. : 2:3 or 1:1.5

incomplete combustion producing carbon (soot) and water. : 1:1

Question 7

why is carbon monoxide dnagerous (2)

Answer 7

once it enters teh bloodstream carbon monoxide binds to hemoglobin molecules in teh red blood cells, blocking teh site where oxygen and carbon dioxide normally bind. This lowers teh oxygen carrying capacity of teh blood.

Question 8

how is carbon monoxide poisoning treated? (how does it work )(2)

Answer 8

it is treated by the inhalation of pure oxygen at higher-than-normal atmospheric pressure, this displaces the carbon monoxide molecules attached to the hemoglobin molecules.`

Question 9

what is produced when a metal reats with an acid

Answer 9

metal + acid —- salt + hydrogen

Question 10

in teh recativity series what does hydrogen indicate

Answer 10

metals above hydrogen in the reactivity series can displace the hydrogen ion from acid solutions in the reaction between a metal and an acid. (thereofre it will react with acids )

Question 11

reactivity reflects …..(2)

Answer 11

reactivity reflects the ease woth which a metal loses its valance electrons. More reactive metals will lose electrons quicker.

Question 12

what is an electrode

Answer 12

an electrode is a substance through which an electric current enters or leaves teh non-metalic part of teh electrochemical cell

Question 13

oxidation which electrode, reduction which electrode

Answer 13

oxidation at teh anode, reduction at teh cathode

Question 14

there is a net movement of elctrons from ?

Answer 14

anode to the cathode

Question 15

why are non-metals high in group 17 powerful oxidisung agents

Answer 15

string tendancy to gain electrons and becom e reduced

Question 16

what is a fuel (2)

Answer 16

a fuel is something which can burn to produce energy. Any substance which upon combustion produces a usable amount of energy is known as fuel.

Question 17

complete combustion ( 2 points )

Answer 17

plenty of oxygen available, carbon dioxide and water produced

Question 18

incomplete combustion (3 points )

Answer 18

not enough oxygen availablem carbon monoxide and soot produced, dirst (black/gray) flame produced

Question 19

fancy fro not enough oxygen

Answer 19

oxygen is a limiting reagent

Question 20

what is combustion

Answer 20

Combustion is another word for burning. In a combustion reaction, fuel is burned and reacts with oxygen to release energy in teh form of heat and light.

Question 21

what type of a rection is combustion ? What si produced in a combustion reaction of something that only contaings hydrogen and carbon >

Answer 21

oxidation recation, carbon dioxide and water are prdoyced

Question 22

why is carbon monoxide dangerous ? (3,2)(human, environment)

Answer 22

Carbon monoxide is a poisonous gas which binds to haemoglobin in your red blood cells, preventing them from carrying oxygen to the cells in your body. Carbon monoxide is colourless and has no smell, so it is very difficult to tell if you are breathing it in. It can be detected by electronic detectors which are often fitted near to boilers.

Particulate carbon can cause health problems for humans because it irritates the lining of the lungs, can make asthma worse, and perhaps even cause cancer. Particulate carbon can also cause global dimming, which may reduce rainfall.

Question 23

metal + acid ———– ?

Answer 23

salt + hydrogen

Question 24

what does hydrogen signify in teh reactivity series ?

Answer 24

metals above hydrogen in teh reactivity series can displace hhydrogen from an acid.

Question 25

Purpose of salt bridges

Answer 25

Salt bridge
balances out the
negative charge
built up and the
positive charge
built up in each
half cell

The purpose of the salt bridge is to act as a source of spectator ions that can migrate into each of the half cells to preserve neutrality.

Question 26

Which electrode do the electrons move towards? Why? ( voltaic cell )

Answer 26

Electrons move towards the cathode because reduction needs to take place at the cathode
(needs an excess of electrons)

Question 27

what is corrosion

Answer 27

corrosion is the process of deterioration of a substance due to cehmical, electrochemical or other reactions taht take place on teh surface of that substance

Question 28

how is corrosion of a metal prevented ?

Answer 28

Corrosion of a metal is prevented by
coating with something which does not
allow moisture and oxygen to react with
it.

Question 29

what si electroplating

Answer 29

Electroplating is a technique in which a thin layer of a
desired metal is used to coat (or “plate”) another object
by electrolysis.

Question 30

what is rusting

Answer 30

Rusting is a specific example of corrosion, which occurs when iron or steel reacts with oxygen and water: results in teh formation f iron oxide

Question 31

Explain how silver-plated cutlery are
created ( 5 poinst )

Answer 31

Fork electrode = cathode
(reduction)
* Positive silver ions(Ag+) from
the electrolytic solution will be
attracted to the cathode
causing the deposition of solid
silver.
* The Ag+ will come from the
electrolytic solution. As they get
used up, they will need to be
replaced.
* The silver bar (Ag) will be the
source of new Ag+.
* The bar will act as the anode
and undergo oxidation. It gets
thinner as it produces new Ag+.

Question 32

hwo to hydrogyn fuel cells work (complcated)(3)

Answer 32

Hydrogen gas enters the fuel cell through the anode. In the anode, the atoms of hydrogen create a chemical reaction with a catalyst, splitting into protons and electrons. At the same time, oxygen from the atmosphere enters the fuel cell via the cathode. (The catalyst, typically made of platinum particles, facilitates the chemical reaction).
There is a porous electrolyte membrane between anode and cathode. The protons pass through it. From the other side, the electrons flow out of the cells, creating electricity. This electricity can then be used to run an electric propulsion system.
In the cathode, the oxygen and protons then combine to produce water.

Question 33

hwo do hydrigen fuel cells work ( easy)

Answer 33

hydrogen fuel cell combines oxygen and hydrogen to form water and create electricity.

Question 34

hwo do hydrigen fuel cells work ( easy)

Answer 34

hydrogen fuel cell combines oxygen and hydrogen to form water and create electricity.

Question 35

bioleaching

Answer 35

using bacteria ro extract metals from theri ores

Question 36

what determines wether hydrogen or a metal will be formed at the cathode ? (3)

Answer 36

Whether hydrogen or a metal is produced at the cathode depends on the position of the metal in the metal reactivity series:

the metal will be produced at the cathode if it is less reactive than hydrogen
hydrogen will be produced at the cathode if the metal is more reactive than hydrogen

Question 37

at teh anode when is oxygen prodcused and when is it not ?

Answer 37

Oxygen is produced (from hydroxide ions) at the anode, unless halide ions (chloride, bromide or iodide ions) are present. In that case, the negatively charged halide ions lose electrons and form the corresponding halogen (chlorine, bromine or iodine).

Question 38

Why must aluminium oxide be heated during the extraction of aluminium? (2)

Answer 38

Aluminium oxide is heated to allow ions to move during electrolysis. It is dissolved in molten cryolite, reducing the temperature needed for electrolysis to happen.

Question 39

What is produced at the carbon anode during the electrolysis of aluminium oxide?

Answer 39

Carbon dioxide is produced at the carbon anode. Oxygen is produced first but it then reacts with the carbon electrodes.

Question 40

Galvanic/Voltaic vs Electrolytic cells energy derivation

Answer 40

Galvanic cells derives its energy from spontaneous redox reactions, while electrolytic cells involve non-spontaneous reactions and thus require an external electron source like a DC battery or an AC power source.

Question 41

Salt bridge purpose and what it contains

Answer 41

The salt bridge contains an inert electrolyte like potassium sulfate whose ions will diffuse into the separate half-cells to balance the building charges at the electrodes.

Question 42

Voltaic cell (mnemonic )

Answer 42

Red Cat An Ox