Many of the substances that we use every day have to be made from other chemicals. This may involve using complex chemical reactions. Examples include food colourings, flavourings and preservatives, the ink in your pen or printer, and the artificial fibres in your clothes. All of these are made using chemical reactions.
Imagine a reaction: A + 2B ---> C
If we need 1000kg of C, we can work out how much A and B we need. All we need to know is the relative formula masses of A, B and C and the balanced symbol equation.
If we carry out the reaction, it is unlikely that we will get as much of C as we…