Which is the correct way to do this math problem?

[pharmacist007]

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How many ml of chemical are required to make 41.4g of a 30% (w/w) solution with a specific gravity of 1.15?

pronto pass has it as...

30g/100g = x/41.4g x= 12.42g

1.15 = 12.42/x answer= 10.8ml

ansel book has it as...

30g/100g = 41.4g/x x= 138g

1.15= 138g/x answer= 120ml

I'm so confused

 

[killerpenguin21]

you need to know how much chemical is in the given 41.4g of the 30% solution.

the ansel first step is finding the volume of solution not the amount of chemical in a given volume.

 

[beehappy32832]

Dear Pharmacis007:

I have prontopass math 2010 version 10.1 and prontopass math 2006 version 6.5. Both versions have this exercise under section 5H. Both of them have the same answer-explanation. Their answer does not match at all with the information you are giving us in your post.

Q. How many gm of a chemical are required to make 120ml of a 30% (w/w) solution having a specific gravity of 1.15?

A. Step 1. Determine total weight of solution:
120ml*1.5=138gm
Step 2. How much is needed to make 30% w/w?
138*30%=41.4g

I hope this clarification helps all of us.

All the best for you