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Question 1 of 3

Compound Benzoic Acid Ointment BP 1988 contains 12 grams of Benzoic Acid in 200 grams of ointment. What is the concentration % w/w of the Benzoic Acid in the ointment?

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% w/w
The concentration of Benzoic Acid is 6 % w/w.
EITHER
 % w/w = mass of component x               100                     (g/100 g)
mass of product
% w/w Benzoic Acid = 12 x    100         (g/100 g)
200
% w/w Benzoic Acid = 6

OR
 200 g of ointment contains 12 g of Benzoic Acid
Thus: 100 g of ointment contains    100    x 12 g of Benzoic Acid
200
100 g of ointment contains 6 g
Concentration of Benzoic Acid is 6 g/100 g ie 6 % w/w

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Question 2 of 3

750 g of Zinc and Coal Tar Paste BP 1988 are prepared. If the paste contains 45 grams of Zinc Oxide, what is the concentration % w/w of the Zinc Oxide in the paste?

Type in your answer and PRESS ENTER.
% w/w
The concentration of Zinc Oxide is 6 % w/w.
EITHER
 % w/w = mass of component x               100                     (g/100 g)
mass of product
% w/w Zinc Oxide = 45 x    100         (g/100 g)
750
% w/w Zinc Oxide = 6

OR
 750 g of paste contains 45 g of Zinc Oxide
Thus: 100 g of paste contains    100    x 45 g of Zinc Oxide
750
100 g of paste contains 6 g of Zinc Oxide
Concentration of Zinc Oxide is 6 g/100 g ie 6 % w/w

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Question 3 of 3

A powder for colds contains 600 mg of Paracetamol in a total of 6 g of the powder. What is the concentration % w/w of Paracetamol in the powder?

Type in your answer and PRESS ENTER.
% w/w
The concentration of Paracetamol is 10 % w/w.
EITHER
Convert the mass in milligrams to grams: 600 mg = 0.6 g
% w/w = mass of component x               100                     (g/100 g)
mass of product
% w/w Paracetamol = 0.6 x 100      (g/100 g)
6
% w/w Paracetamol = 10
OR
 6 g of powder contains 0.6 g of Paracetamol
Thus: 100 g of powder contains 100 x 0.6 g of Paracetamol
6
100 g of powder contains 10 g of Paracetamol
Concentration of Paracetamol is 10 g/100 g ie 10 % w/w

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