exam math questions

by Brittany
(TX)

Hey guys, I finished the pharm tech program at the end of may and have been studying since then for the certification exam (which i take tomorrow). I somewhat understand the solution dilution and concentration and proportion problems but I have problems when I read the question as to which formula to use? I have a few example questions from the mosby's practice CD if I put them on here could someone show me step by step how to solve? Also are there any hints as to how to figure out which formula to use for a problem?

How many ml's of water must be added to 250ml of a 0.9% w/v stock solution of sodium chloride to prepare 1/2 NS solution?

How many ml's of a D10W solution contain 100g of Dextrose?

What is the % strength of a solution that is made by adding 100ml of water to 600ml of a 25% solution?

How many grams of zinc oxide would contain 10g of zinc oxide?

Comments for
exam math questions

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Aug 08, 2011
MATH EQUATION
by: Anonymous

HOW MANY GRAMS OF 20 PERCENT OF ZINC OXIDE OINTMENT,WOULD CONTAIN 10 GRAMS OF ZINC OXIDE

Mar 23, 2011
exam math questions
by: Anonymous

How did you get 2.25g? When I multiply 0.9 by 250 I get 225g. Am I missing something?

Jul 07, 2010
3RD QUES ANS
by: Anonymous

What is the % strength of a solution that is made by adding 100ml of water to 600ml of a 25% soluTION.

U WILL FIND GRAMS OF SOL...
SO
X/600=25/100
X=150G

SO THE TOTAL RATIO COMES LIKE 150G/700ML BY ADDING 100ML OF WATER INTO 600ML

TOTAL % COMES BY

150/700=X/100

X=21%

Jul 07, 2010
2ND QUES ANS
by: Anonymous

How many ml's of a D10W solution contain 100g of Dextrose?

ANS IS AS FOLLOW

D10W MEANS IT IS 10% SOL. THAT MEANS IT IS 10G/100ML

SO
100G/X=10/100
X=1000ML OR 1L

Jul 07, 2010
IST QUES. ANS.
by: Anonymous

How many ml's of water must be added to 250ml of a 0.9% w/v stock solution of sodium chloride to prepare 1/2 NS solution?

answer is as follow...

X/250=0.9/100

X=2.25G

2.25/X =0.45/100(1/2 NS SOL)

X =500
TOTAL WATER NEEDED = 500-250=250

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