Question

Bactroban ointment contains 2% w/w mupirocin. How many grams of a polyethylene glycol ointment base must be mixed with the contents of a 22-g tube of the bactroban ointment to prepare one having a concentration of 5mg/g? Answer: 66g polyethylene glycol ointment base

Answer 1

22 x 0.02 = 0.44 g  

If y = no. of g of base  

After we mix , we will have (22 + y) grams of that mixture, and the concentration will be 5 mg.

5 mg = 5 / 1000 = 1 / 200

0.44 / (y + 22) = 1/200  

44 / 100 = (y + 22) / 200  

44 = (y + 22) / 2  

88 = y + 22  

y = 66 g