Chemistry (random questions)

• Audi

  8 Oct 09, 01:26

  1. when copper is extracted from its ore, it contains carbon impurities. suggest how the carbon impurities get into the copper.

  My reasoning: copper is low in reactivity, so it can be obtained through reduction by carbon and during this extraction process, carbon impurities get onto the copper.

  2.when Fe is extraced from haematite in the blast furnacem waste gases and solid waste products are formed.

  name the 3 main waste products (N2 , CO, CO2)

  I know N2 is produced as waste gas, but is there any equation to prove its formation?

  Thanks everyone!

• dkcx

  8 Oct 09, 02:16

  Originally posted by Audi:

  1. when copper is extracted from its ore, it contains carbon impurities. suggest how the carbon impurities get into the copper.

  My reasoning: copper is low in reactivity, so it can be obtained through reduction by carbon and during this extraction process, carbon impurities get onto the copper.

  2.when Fe is extraced from haematite in the blast furnacem waste gases and solid waste products are formed.

  name the 3 main waste products (N2 , CO, CO2)

  I know N2 is produced as waste gas, but is there any equation to prove its formation?

  Thanks everyone!

  N2 should not appear in the blast furnace if i didn't recall wrongly since only oxygen is pumped into the blast furnace. However if N2 is really present then it can be said that its present in the air pumped into the blast furnace and it stays unreacted throughout the entire process. 1 of the waste product is the slag (CaSiO3) formed during the reaction. CO should not be considered a waste product as it is used as part of the reaction process.

• UltimaOnline

  8 Oct 09, 07:02

  That's right : N2 is neither a reactant nor a product in this process. Both C and CO are the relevant reducing agents for this industrial process (think critically : any locational differences within the blast furnace that each reducing agent plays a more dominant role over the other?). So far from being a "waste product", CO is a desirable reactant required to generate the desirable product.
• Audi

  8 Oct 09, 07:24

  Hallo.

  One of my friends' silbing passed me his TYS and the question, if i remember correctly, asks candidates to name 3 waste gases during extraction of iron from blast furnace. My answers, are stated, as above. However answers the publishers gave does not include N2, but CaO, which I think is even impossible to think of since CaO exists as solid form. What do you think?

  Thanks once again.

• UltimaOnline

  8 Oct 09, 07:43

  The term "waste gases" here refer to the fact that gases that must be allowed to leave due to thermal expansion and pressure differences - bear in mind that new air is constantly being pumped into blast furnace because additional oxygen and carbon dioxide is continuously required for this industrial process (to react with C to generate CO). In which case, the "waste gases" that must be allowed to leave naturally includes N2, CO and CO2 (and naturally some, but relatively little, of unreacted oxygen, H2O vapour, noble gases, oxides of nitrogen, oxides of sulfur, etc etc), even though these may not be "wastes" in the sense of the word. So, as far as this particular question is concerned (two additional relevant points : 'O' level questions are simplified, so it's far easier to simply ask the student summarily thusly, rather than an essay discussion on every subpoint; even Cambridge exam questions may be argued to have some aspects of flaw or fault in regards to interpretation), then the best answer would indeed be : CO, CO2 and N2. Although one might argue that oxides of nitrogen and sulfur are more polluting than N2, but these are not present in significant amounts. Bottomline : the question isn't actually asking "what are the waste gases from the process occurring in the blast furnance?" but is asking "what are the main chemical gases present in the waste gases released from the blast furnace?" See the difference?