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Question: zinc and castor oil ointment zinc oxide 75 g castor...

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ZINC AND CASTOR OIL OINTMENT 

Zinc oxide 7.5 g

castor oil 50.0g 

cetostearyl alcohol 2.0 g

white beeswax 10.0 g 

arachis oil 30.05 g

The Wt/mL of castor oil is 0.95g

 

The volume of castor oil required to make 500 g of this ointment is?

 

***The answer that I was given was this: but I DO NOT understand why we got 1/0.95? why do we divide 1 by 0.95? does'nt wt/ml mean weight by mL? I thought it means 0.95/1 mL and not vise versa***

 

For 100 grams of the ointment, we need 50 grams of castor oil is required ( carefully watch the values).

 

For 500 grams of the ointment, we will need castor oil= 50/100*500= 2500 grams of castor oil.

 

 As we are given, 0.95g of castor oil in 1 ml of castor oil.

 

So 2500 grams of castor oil is 1/0.95*2500 which is equal to 263 mL.

 

 

 

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