Mole calculations
To calculate the mass of a higher number of moles, or even calculate the number of moles in a certain mass, a formula triangle can be used.
Using the formula triangle is straightforward. Simply cover whatever part of the triangle you are trying to work out.
Example one
How many moles are present in 25 g of calcium carbonate?
The formula we need to use, given by covering up number of moles is:
\(number\,of\,moles = \frac{{mass}}{{formula\,mass}}\)
The formula mass of calcium carbonate can be calculated using the formula and values from the data book and the mass is given in the question.
\(= \frac{{25}}{{100}}\)
\(= 0.25moles\)
Example two
Calculate the mass of 0.25 moles of butane \({C_4}{H_{10}}\).
\(mass = number\,of\,moles \times formula\,mass\)
\(\begin{array}{l} = 0.25 \times 58\\ = 14.5g \end{array}\)