2.AMOUNT Of SUBSTANCE

Ibuprofen is an anti-inflammatory medicine that was first patented in the 1960s. It is now available without prescription (‘over-the-counter’), and is sold under several different brand names, such as Nurofen and Ibuleve. The early manufacture of ibuprofen involved a series of six different chemical reactions, but each stage generated unwanted products. This meant that there was a lot of waste, which was associated with expense and the potential for environmental harm. The process also resulted in only 40.1% of all the atoms in the reactants ending up in the ibuprofen molecules. During the 1990s, BootsTM developed an alternative process for the manufacture of ibuprofen that involved only three stages. Less waste was produced and 77.4% of atoms in the reactants ended up in the ibuprofen molecules. Scientists use the idea of atom economy to calculate percentages of waste products. You will find out more about atom economy in this chapter.

You read in Chapter 1 that we use relative atomic mass and relative molecular mass to compare the masses of atoms and molecules. You may already know how to use a chemical equation to describe a chemical reaction.

You may have also learned how chemists use moles to count particles and you have possibly carried out some calculations using moles.

In this chapter on amounts of substance you will build on these ideas and learn how amounts of chemical substances in solids, liquids, gases and solutions can be measured in moles.