Oxidation reaction + Nuclear chemistry

Question 1

What is a displacement reaction?

Answer 1

• ions are displaced from solution, losing their outer shells
• One substance donates electrons to another
• one metal dissolves to become ions, the other comes out as a solid

Question 2

When do redox reactions occur spontaneously?

Answer 2

in the direction that has positive potential (produces electricity)

• *If a redox reaction has positive potential this means no energy has to be input into the reaction
• • if it has negative potential, energy will be put in to make the reaction occur

Question 3

What do galvanic cells do?

Answer 3

They allow for a redox reaction to occur

Question 4

What are the parts of a galvanic cell?

Answer 4

Electrodes:
-Cathode: reduction occurs (+electrode)
-Anode: oxidation occurs (-electrode more reactive metal)
Electrolyte: SOLUTION OF IONS which appear to conduct e-
Salt bridge: connects cells and MAINTAINS NUTRALITY

Question 5

What are the factors influencing galvanic cells?

Answer 5

MAIN FACTOR:
the standard conditions of 25 degrees celcius, 1 M/Lsolution electrolyte

MINOR FACTOR:
-corrosion of electrodes/wiring, faulty voltmeter

Question 6

What is an oxidation state?

Answer 6

a number that tells you how many electrons an atom has lost (or gained)

Question 7

Oxidation states increase when?

Oxidation states decrease when?

Answer 7

an element/atom loses electrons (is oxidised)

When an atom gains electrons (becomes negative)

Question 8

What are the rules of oxidation states

Answer 8

-oxidation increases OS, reduction decreases OS
-elemental form means zero oxidation state
-The charge on a single ion equates to its OS
-Hydrogen is always 1+ when in compounds
EXCEPT in metal hydrides eg. NaH (it is -1)
-Oxygen is always 2-in compounds except w fluorine & peroxide compounds (-1)
-The OStates of the parts of a compound add up to the compounds total charge (OS)

Question 9

What is the structure of a lead-acid battery?

Answer 9

-6 Cells in series (2V each) = total output 12 V
-In each cell:
Anode: prous lead sheet
Cathode: Lead IV Oxide
Electrolyte: 35% solution of Sulfuric Acid
**charge can be determined by measuring concentration of H ions

Question 10

What are the anode and cathode reactions for a lead acid battery?

Answer 10

Anode oxidation:
lead + sulfate ion –> leadsulfate + 2e-
Pb(s) +SO42-(aq) –> PBSO4(s) + 2e-

Cathode reduction:
Lead oxide + sulfate ion + 4H+ + 2e- –>
lead sulfate + water
PbO2(s) +SO42- +4H+ + 2e- –> PBSO4(s) + 2H2O(l)

Question 11

What is the structure of the Hydrogen fuel cell?

Answer 11

-One cell producing 0.7V
Anode & cathode:
both platinum catalyst on graphite coated paper
Electroylyte: Flurocarbon polymer with sulfonic acid functional groups
**requires constant fuel(H gas) and oxidant (oxygen gas) input

Question 12

Compare the cost and practicality of lead acid battery and hydrogen fuel cell

Answer 12

Lead Acid Battery:

1. Expensive due to lead content
2. Rechargeable (lasts many years)
3. Large and heavy (not portable, limited practicality)

Hydrogen Fuel Cell

1. Requires constant input of H2(g) ( an expensive gas, also explosive, hence dangerous)
2. It is expensive due to platinum development
3. It is compact and light weight with no moving parts ( more useful in portable applications)

Question 13

Compare the impact of lead acid battery and hydrogen fuel cell on the society and environment

Answer 13

Lead Acid Battery:
1. Widely used to start cars {greater impact on society}
2. Good at power storage & is reliable (rechargeable)
Enviro:
-there are eventual disposal issues with toxic lead & corrosive sulfuric acid, polluting the environemnt

Hydrogen Fuel Cell:
1. Limited use (mainly used in space craft or remote locations) (Has potential use in cars) {little impact on society}
2. Good at power storage & is reliable (can be started up at any time as long as fuel is available)
Enviro:
-Environmentally friendly & renewable: water is the only product (uses no fossil fuels)

Question 14

What are the anode and cathode reactions for Hydrogen fuel cell?

Answer 14

oxidation anode reaction:
H2(g) –> 2H+ + 2e-

Reduction cathode reaction:
4H+ + 4e- + O2(g) –> 2H2O(g)

Question 15

What is an isotope?

Answer 15

Same atomic number, different atomic mass (same NO. protons, different No. neutrons)

Question 16

What is radioactivity?

What are radioisotopes?

Answer 16

The emission of radiation due to an unstable nucleus

-Radioisotopes are unstable radiation emitting nuclei

Question 17

What are the causes of nuclear unstability?

Answer 17

-elements less than 20 atomic number: Z<20
ratio p:n is 1:1
-elements 20-50 ration p:n is 1:1.3
-elements 50-83: ratio p:n is 1:1.5
-elements above 82 (pb) are all radioactive

Question 18

What are alpha particles?

Answer 18

helium nuclei ( 2 protons, 2 neutrons)

Question 19

When does alpha decay/radiation occur?

Answer 19

when there are too many protons in the nucleus, a helium nucleus is emitted, (loses 2 protons)

Question 20

When does Beta decay/radiation occur?

Answer 20

When n:p ratio is too high.
In beta decay a neutron is transformed into a proton and an electron, the electron is then emitted (you get one more proton)

Question 21

When does gamma decay/radiation occur

Answer 21

when there is excess energy in the nucleus, because gamma rays are a form of energy

Question 22

What are commercial isotopes and transuranic elements?

Answer 22

isotopes used for commercial use

elements above 92 (after Uranium) aren’t naturally occuring

Question 23

How are commercial isotopes and transuranic elements produced?

Answer 23

1. Particle Accelerators
   - nucleii is collided at close the speed of light making them combine (new element)
2. Neutron Bombardment
   - Fires neutrons which are absorbed by the target nucleii increasing n:p and causing beta decay –> new element

Question 24

What are some recently discovered elements?

Answer 24

Unumpentium Uup (2004 discovered) element 115

Unumoctian Uuo (2006) element 110

Question 25

What are instruments used to detect radiation?

Answer 25

• Geiger Counter ( Geiger muller tube)
• Cloud chamber
• Film badges
• Scintillation counter

Question 26

How do the Geiger counter and Cloud chamber detect radiation?

Answer 26

Geiger counter: uses ionising properties of radiation. radiation ionises argon molecules in the tube, this ejects electrons, forming a current which registers a click. The more radiation –>more clicks *better at registering alpha prticles.

Cloud chamber: uses alcohol vapour. when radiation passes through vapour, it ionises particles, causing condensation to occur. causing a ‘cloud trail’ along the path of radiation. Alpha, beta and gamma leave different trails

Question 27

How do photographic film badges and scintillation counter detect radiation?

Answer 27

• the film becomes exposed in the presence of radiation
  scintillation: a light flashed is produced when radiation hits particles in the counter. Flash is measured electronically

Question 28

What is a medical radioisotope and how is it used in terms of their chemical properties?

Answer 28

Technetium -99m
Properties:
-emits gamma rays
-half life is 6 hours
-reactive, can be attached to mamy different compounds
Use: locating cancers/tumours in body aswell as organ function,
-low ionising ability mean its not too physically damaging.
-Higher penetrating power means it can be detected by instruments.
-short half life means minimal exposure to harmful radiation

reactivity means it can be attached to compounds that travel around the body, testing organ function.

**doesn’t diagnose

Question 29

What is an industrial radioisotope and how is it used in terms of their chemical properties?

Answer 29

Cobalt -60
properties:
-under goes beta decay and gamma
-half life of 6 years
-chemically inert
Use:
gauging thickness of materials.
-radioisotope is placed on one side and radiosensitive film on the other
Gamma can penetrate metal ( too much radiation= too thin
too little radiation =too thick)
half life of 6 years and chem inert: means little maintenance

Question 30

What are the benefits and problems associated with the use of radioactive isotopes?

Answer 30

Adv:

1. new treatment and diagnostic techniques to improve health care, saving millions of lives
2. medical sterilisation, prevents infection
3. more sensitive and precise monitoring equipment (determining integrity of structure of a product, smoke alarms, silicon doping, fruit fly control)
4. nuclear power-reduces dependence on coal which contributes to climate change as no CO2 gas given off

Disadvantages:

1. doctors/industrial workers more exposed to more harmful radiation –> mutations,cancer (careful monitoring required)
2. radiaoactive wastes have a long half lifeand remain dangerous for centuries, hence serious disposal issues. –> bad for the enviro
3. Nuclear reactors and partical accelerators is $$$. The short half life of many radiosisotopes means many have to be built as can’t be transported easily.

HOwever waste problems can be dealt with through effective management. they are beneficial to society.