Section 3: Calculating the Mass of Product
If you know the % w/w of a component and you know how many grams of that component you have, you can calculate what mass of product is involved.
Compound Aluminium Paste BP 1988 contains 20 % w/w Aluminium Powder. If an amount of paste contains 17 grams of Aluminium Powder, how much paste is there?
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Ratio Solution
A concentration of 20 % w/w Aluminium Powder means
that there are:
20 g of Aluminium Powder in 100 g of Paste.
Thus:
17 g of Aluminium Powder are in 17 x 100 g of Paste
20
17 g of Aluminium Powder are in 85 g of Paste
There are 85 grams of paste.
that there are:
20 g of Aluminium Powder in 100 g of Paste.
Thus:
17 g of Aluminium Powder are in 17 x 100 g of Paste
20
17 g of Aluminium Powder are in 85 g of Paste
There are 85 grams of paste.
Equation Solution
The equation you can use is:
% w/w = mass of component x 100 (g/100 g)
mass of product
mass of product
which rearranges to:
mass of product = mass of component x 100 g
% w/w
% w/w
Mass of Paste = 17 x 100 g
20
Mass of Paste = 85 g
There are 85 grams of the paste.
20
Mass of Paste = 85 g
There are 85 grams of the paste.