Chemistry_Grade_10-12 (1).pdf

A one of the main reasons that south africas gold

Info icon This preview shows pages 432–436. Sign up to view the full content.

View Full Document Right Arrow Icon
(a) One of the main reasons that South Africa’s gold industry has been so economically viable is that... i. gold panning can be used as an additional method to extract gold ii. open cast mining can be used to extract gold reserves iii. South Africa’s geological history is such that its gold reserves are con- centrated in large reefs iv. South Africa has large amounts of water to use in mining (b) The complete list of reactants in an iron blast furnace is... 418
Image of page 432

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHAPTER 21. THE LITHOSPHERE - GRADE 11 21.11 i. carbon and oxygen ii. coal, oxygen, iron ore and limestone iii. carbon, oxygen and iron ore iv. coal, air, iron ore and slag 3. More profits, more poisons In the last three decades, gold miners have made use of cyanidation to recover gold from the ore. Over 99% of gold from ore can be extracted in this way. It allows miners to obtain gold flakes - too small for the eye to see. Gold can also be extracted from the waste of old operations which sometimes leave as much as a third of the gold behind. The left-over cyanide can be re-used, but is more often stored in a pond behind a dam or even dumped directly into a local river. A teaspoonful of 2% solution of cyanide can kill a human adult. Mining companies insist that cyanide breaks down when exposed to sunlight and oxygen which render it harmless. They also point to scientific studies that show that cyanide swallowed by fish will not ’bio-accumulate’, which means it does not pose a risk to anyone who eats the fish. In practice, cyanide solution that seeps into the ground will not break down because of the absence of sunlight. If the cyanide solution is very acidic, it could turn into cyanide gas, which is toxic to fish. On the other hand, if the solution is alkaline the cyanide does not break down. There are no reported cases of human death from cyanide spills. If you don’t see corpses, everything is okay. (a) What is cyanidation ? (b) What type of chemical reaction takes place during this process: precipita- tion, acid-base or redox? (c) Is the pH of the solution after cyanidation greater than, less than or equal to 7? (d) How is solid gold recovered from this solution? (e) Refer to cyanidation and discuss the meaning of the heading of this extract: More profits, more poisons . (DoE Grade 11 Paper 2, 2007) 419
Image of page 433
21.11 CHAPTER 21. THE LITHOSPHERE - GRADE 11 420
Image of page 434

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Chapter 22 The Atmosphere - Grade 11 Our earth is truly an amazing planet! Not only is it exactly the right distance from the sun to have temperatures that will support life, but it is also one of the only planets to have liquid water on its surface. In addition, our earth has an atmosphere that has just the right composition to allow life to exist. The atmosphere is the layer of gases that surrounds the earth. We may not always be aware of them, but without these gases, life on earth would definitely not be possible.
Image of page 435
Image of page 436
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern