Mole and Mass Calculations
These questions are easy marks in exams, once you simply learn how to apply a few equations. Definitely take the time to practice these questions as they can come across intimidating in exams.
Mole/Mass Calculations
When given moles or mass in a question and asked to figure out an unknown value, there is a simple equation you can use.
m = n x gfm
m = mass (grams)
n = number of moles (moles)
gfm = gram formula mass, found in data booklet.
Volume/Concentration Calculations
There is another simple equation you can used to find out missing values of volume, moles or concentration.
c = n/v
c = concentration (moles/litre)
n = number of moles (moles)
v = volume (litres)
Percentage Mass of an Element
It is almost guaranteed that you will be asked to calculate the percentage mass of an element in your exams. This can be done simply with the given equation.
Calculating the amount of an element in a compound is exactly the same as calculating the percentage of this pizza is pepperoni.
The gram formula mass of each element can be found in the data booklet.
Key Points!
-
Mole/Mass Calculations
m = n x gfm
m = mass (grams)
n = number of moles (moles)
gfm = gram formula mass, found in data booklet.
-
Volume/Concentration Calculations
c = n/v
c = concentration (moles/litre)
n = number of moles (moles)
v = volume (litres)
-
Percentage Mass of an Element
% Mass = (Mass of element in 1 mol of compound/molar mass of compound) x 100