Oxidation reaction + Nuclear chemistry Flashcards
What is a displacement reaction?
- 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
When do redox reactions occur spontaneously?
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
What do galvanic cells do?
They allow for a redox reaction to occur
What are the parts of a galvanic cell?
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
What are the factors influencing galvanic cells?
MAIN FACTOR:
the standard conditions of 25 degrees celcius, 1 M/Lsolution electrolyte
MINOR FACTOR:
-corrosion of electrodes/wiring, faulty voltmeter
What is an oxidation state?
a number that tells you how many electrons an atom has lost (or gained)
Oxidation states increase when?
Oxidation states decrease when?
an element/atom loses electrons (is oxidised)
When an atom gains electrons (becomes negative)
What are the rules of oxidation states
-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)
What is the structure of a lead-acid battery?
-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
What are the anode and cathode reactions for a lead acid battery?
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)
What is the structure of the Hydrogen fuel cell?
-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
Compare the cost and practicality of lead acid battery and hydrogen fuel cell
Lead Acid Battery:
- Expensive due to lead content
- Rechargeable (lasts many years)
- Large and heavy (not portable, limited practicality)
Hydrogen Fuel Cell
- Requires constant input of H2(g) ( an expensive gas, also explosive, hence dangerous)
- It is expensive due to platinum development
- It is compact and light weight with no moving parts ( more useful in portable applications)
Compare the impact of lead acid battery and hydrogen fuel cell on the society and environment
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)
What are the anode and cathode reactions for Hydrogen fuel cell?
oxidation anode reaction:
H2(g) –> 2H+ + 2e-
Reduction cathode reaction:
4H+ + 4e- + O2(g) –> 2H2O(g)
What is an isotope?
Same atomic number, different atomic mass (same NO. protons, different No. neutrons)
What is radioactivity?
What are radioisotopes?
The emission of radiation due to an unstable nucleus
-Radioisotopes are unstable radiation emitting nuclei
What are the causes of nuclear unstability?
-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
What are alpha particles?
helium nuclei ( 2 protons, 2 neutrons)
When does alpha decay/radiation occur?
when there are too many protons in the nucleus, a helium nucleus is emitted, (loses 2 protons)
When does Beta decay/radiation occur?
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)
When does gamma decay/radiation occur
when there is excess energy in the nucleus, because gamma rays are a form of energy
What are commercial isotopes and transuranic elements?
isotopes used for commercial use
elements above 92 (after Uranium) aren’t naturally occuring
How are commercial isotopes and transuranic elements produced?
- Particle Accelerators
- nucleii is collided at close the speed of light making them combine (new element) - Neutron Bombardment
- Fires neutrons which are absorbed by the target nucleii increasing n:p and causing beta decay –> new element
What are some recently discovered elements?
Unumpentium Uup (2004 discovered) element 115
Unumoctian Uuo (2006) element 110
