Volume 1

Imagine running a steel mill. The major component of steel is iron, so you need to purchase iron ores for your business. Your supplier, a mining company, offers two different iron ores for the same price per ton,

A molecule of magnetite, Fe

100% - 72.4% = 27.6%

Alternatively, we can divide the total weight of the oxygen atoms in the molecule by the molecular weight and multiply the result by 100%.

(64/232) x 100% = 27.6%

Regardless of the calculation method, the mass percentage of oxygen in magnetite is 27.6% and the mass percentage of iron is 72.4%.

Next, we repeat the calculation for hematite, Fe

Our calculations show that magnetite contains 72.4% of iron by mass, whereas for hematite the figure is 70%. The difference of 2.4% might look minor. But the steel and chemical industries operate on a huge scale. So now think you are to purchase say 10 million dollars worth of either ore. The difference of 2.4% then translates to $240,000 in savings.

Some readers might say that we do not need to know the atomic masses to find out which of the two ores has the higher iron content. If the formulas are Fe

Here is another example. Suppose you want to invest in platinum (Pt). Platinum is more rare and expensive than gold. There is a vendor selling K

Let us first compare K

Next we compare K

The simple considerations above show that the content of Pt by mass diminishes in the order Na

We can also calculate mass percentages of Pt in each of the three compounds. First, the approximate molecular weights of Na

(195/383) x 100 % = 51% Pt for Na

(195/415) x 100 % = 47% Pt for K

(195/486) x 100 % = 40% Pt for K

Although herein we skip details of how the atomic masses were determined in the original studies, one example below can give you an idea. Knowing the composition of a compound comprising two elements and the atomic mass of one of the two, one can determine the atomic mass of the other element. For example, methane, the main component of natural gas, has the formula CH

1. Calculate mass percentages of each element in the following compounds: (a) CaO, (b) Al

2. You want to invest in gold. There is a vendor selling gold trichloride (AuCl