To calculate the molecular mass of Glucose we need to know the molecular formula for Glucose. This is:
First we must multiply the atomic mass of each element (Carbon, Hydrogen and Oxygen) by the number of atoms of that element (six, twelve and six).
Six atoms of Carbon ~ 6 (No of atoms) times 12 (atomic mass of Carbon) = 72
Twelve atoms of Hydrogen ~ 12 (No of atoms) times 1 (atomic mass of Hydrogen) = 12
Six atoms of Oxygen ~ 6 (No of atoms) times 16 (atomic mass of Oxygen) = 96
Now we add these three numbers together to get the molecular mass of Glucose.
72 + 12 + 96 = 180
So the molecular mass of Glucose is 180
If you have understood this, you should be able to calculate the molecular mass of sucrose:
You should be able to calculate any molecular mass from a molecular formula: you can use my periodic table to lookup atomic masses.
Now you could try calculating the molecular mass of an inorganic substance. The molcular formula for Aluminium Sulphate is:
This shows TWO atoms of Aluminium, THREE atoms of Sulphur and TWELVE atoms of Oxygen (the “3” multiplies everything inside the brackets).
Aluminium ~ 2 times 27 = 54
Sulphur ~ 3 times 32 = 96
Oxygen ~ 12 times 16 = 192
54 + 96 + 192 = 342
So the molecular mass of Aluminium Sulphate is 342
If you understand this, you can do the calculation for any inorganic substance.