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An introduction to geology
An introduction to geology

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2.6 Getting bauxite from soda cans

A typical bauxite ore is 50% Al2O3. Remember, Al has an atomic mass of 27, O is 16, so bauxite is 26.5% Al. Using this information, see if you can complete the activity below. Again, don't worry if you have some difficulty with this – it takes some practice.

Activity _unit2.7.1 Activity 2.1 Extracting Al from bauxite

Timing: Allow about 10 minutes

How much bauxite do you need to make a 15 g soda can?

a. 

134 g


b. 

56.7 g


c. 

30.1 g


The correct answer is b.

Answer

The answer is 56.7 g bauxite:

50% bauxite is 50% Al2O3.

50 postfix times percent cap a times l sub two times cap o sub three times prefix multiplication of 54 divided by 102 postfix times postfix times equals percent cap a times l

equation left hand side 15 times g times cap a times l divided by 26 times eight divided by 17 postfix division 100 equals right hand side 56 postfix times two divided by three times g postfix times cap b times a times u times x times i times t times e postfix times

So it’s around four times more efficient to use bauxite as a source of Al than a typical igneous rock like granite – and that’s because the geological process, in this case weathering, does a lot of the work for us.