Mass percentage- Definition and calculations
Mass percentage– Definition
Mass percentage is a method used to represent the concentration of an element in a compound or a component in a mixture. The mass of 1 mole of a compound is the sum of all the masses of the moles of its component elements.
Mass percentage is calculated as the mass of a component divided by the total of the mixture, multiplied by 100%, We can calculate the percentage by mass of a component element of a compound from its formula.
Mass percentage– Calculations
Example: Calculate the percentage mass of nitrogen in Trioxonitrate (v) acid (HNO3). ( H= 1 , N=14 , O=16)
The molecular formula of Trioxonitrate (v) acid is HNO3 and in one mole of HNO3 there is 1 of Hydrogen, 1 mole of Nitrogen, and 3 moles of Oxygen.
So the collective molar masses of all the given elements in grams is given as ;
(1 × 1 + 1 × 14 + 1 × 16) = 63g
63g of HNO3 contains 14g of Nitrogen
We can therefore calculate the percentage by mass of nitrogen in HNO3
= 14 / 63 × 100% = 22.2%
Now let’s try a more difficult example;
Calculate the mass percent of silver in AgCl.
Now if you’re not familiar with the periodic table and it’s elements, this question is going to be a real brain knocker for you because the atomic masses weren’t given making it even harder.
Ag is the chemical symbol for silver ( the 47th element on the periodic table ) which has an atomic mass of 107.87
And Cl is the chemical symbol for chlorine ( the 17th element on the periodic table ) and has an atomic mass of 35.453
Now that we have their atomic masses we can go on to calculating it.
(1 × 107.87 for silver) + ( 1× 35.453 for chlorine )
107.87 / 143.23 × 100%
So the mass percent of silver in AgCl is 75.31%
Fun fact; If you exposed a glass of water to space, it would rather boil rather than freeze