Qualification > Sciences
Chemistry P3 7/6/2010
SoONa:
hello .. hope everyones doing well
can some1 please tell me wht i need 2 kno for thermal decomposition for 2mrrw
thanks in advance :D
contraentry:
--- Quote from: SoONa on June 06, 2010, 07:41:26 pm ---hello .. hope everyones doing well
can some1 please tell me wht i need 2 kno for thermal decomposition for 2mrrw
thanks in advance :D
--- End quote ---
Metal Nitrate:
(upon heating)
Group 1: Metal Nitrate > Metal Nitrite + Oxygen
Group 2 & Others : Metal Nitrate > Metal Oxide + Nitrogen Dioxide + Oxygen
Metal Hydroxide :
(upon heating)
Group 1 : No Decomposition
Group2 & Others : Metal Hydroxide > Metal Oxide + Water
Metal Carbonate:
(upon heating)
Group 1: No Decomposition
Group 2 & Others : Metal Carbonate > Metal Oxide + CarbonDioxide
contraentry:
Best of luck to all attempting the Chemistry Paper 3 tomorrow, hopefully it'll be good, and we will all score good marks!
Dana:
--- Quote from: J.Darren on June 06, 2010, 06:03:51 pm ---6.2 Production of energy
-Describe the production of heat energy by burning fuels
Buring fossil fuels, such as coal, natural gas and petroleum (crude oil) produces heat energy.
-Describe hydrogen as a fuel
Pros : Does not produce oxides of nitrogen when buring, the most energy rich fuel, only product of combustion is water.
Cons : Expensive and difficult to store
-Describe radioactive isotopes, such as 235 U, as a source of energy
Heat energy and then electrical energy is produced from nuclear reactors.
-Describe the production of electrical energy from simple cells, i.e. two electrodes in an electrolyte.
Electrons flow from the negative electrode to the positive electrode through the external circuit in an electrolytic fuel cell (also electrolysis).
Zinc electrode, Copper electrode and dilute Sulphuric acid electrolyte are used as an example here.
Since Zinc is more reactive than copper, it is the negative electrode, oxidation takes place (Zn -> Zn2+ + 2e-). The electrons flow through the external circuit to the Copper electrode, the positive ion from the electrolyte (i.e. Hydrogen ions) gets reduced here.
The greater the difference between the reactivity of the two metal electrodes used, the greater the voltage of the circuit would be.
-Describe the use of hydrogen as a potential fuel reacting with oxygen to generate electricity in a fuel cell
Hydrogen is supplied to the negative electrode : H2 -> 2H+ + 2e-
The electrons flows through the external circuit to the positive electrode.
Oxygen is supplied to the positive electrode : O2 + 2H2O + 4e- -> 4OH-
The ions react to produce water : H+ + OH- -> H2O
The overall reaction is : 2H2 + O2 -> 2H2O
When hydrogen reacts with oxygenm to form water in a fuel cell, electrical energy is procued.
--- End quote ---
hey isnt zinc placed as the ANODE not cathode in the cell? or is this electrolysis? :S aakh im so confused. cuz there was a qs in 08 or 07 i dno and it was like gsacrificial protection using tin as the anode and the steel as the cathode. the tin lost electrons, giving them to steel to prevent the steel form oxidising.
Vin:
--- Quote from: Dana on June 06, 2010, 08:51:18 pm ---hey isnt zinc placed as the ANODE not cathode in the cell? or is this electrolysis? :S aakh im so confused. cuz there was a qs in 08 or 07 i dno and it was like gsacrificial protection using tin as the anode and the steel as the cathode. the tin lost electrons, giving them to steel to prevent the steel form oxidising.
--- End quote ---
Um, does this help?:: https://studentforums.biz/index.php/topic,1411.msg254665.html#msg254665
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version