Pharmacy Calculations for Technicians - Concentrations and Dilutions

This video explains a couple of methods to solve concentration and dilution problems in the pharmacy.

[paulasmith]

7 years later and you’re still helping me pass my classes! You’re a blessing for making these and being such a good teacher!

[Gingersnapgrl]

This was exactly what I needed. Math always makes more sense when you watch someone else do it. Thank you so much!

[eternalsummer]

You're a better teacher than the one I have right now. Thanks for these videos!

[ghost]

Thank you for taking a step back with this and showing us what the basis for the math is. To many programs just tell you the formulas and send you on your way!!

[chrisharris]

I'm going through these again as we hit the math portions of Pharmacy 260, thank you so much for these videos Dr. Brad!

[staceylewis]

You are a life saver! I was soooo lost and confused but V1C1=V2C2 makes things 100% easier. Thank you

[brandeebell]

Thank you for this! Online classes can be really confusing and this really helped me understand what my teachers power point was explaining. I appreciate it!

[BradWojcikPharmD]

Hi Stacy,
Thanks for the nice comment. When I teach this course, I tell the students they don't have to memorize any formulas, but if they do want to learn one, learn V1C1=V2C2. You can do the problems without using the formula, but it really comes in handy.
-Dr. Brad

[ggsksandika]

Thank you soo much Brad, you made my life. I have no words to explain how thankful I am.

[RaviProf]

Excellent job. Thanks for sharing valuable information.

[BradWojcikPharmD]

Hi Chris,
Glad they help you. Let me know if you need any help on any problems.

[helenbarela-schneiderman]

Hi Brad,
I wanted to say THANK YOU for your great videos!!!!

[BradWojcikPharmD]

Hi Matyuktanya,
There are a lot of prefixes in the metric system, but in pharmacy the ones that we use most are milli- (one thousandth), micro-(one millionth) and kilo- (one thousand). If you learn that 1 g =1000 mg, 1 mg=1000 mcg, 1 L = 1000 mL, 1 kg = 1000 g you will be able to do 99% of all the problems. You can remember that kilo- means 1000 by thinking about a kilometer (kilo-meter). It is 1000 meters, Look at a ruler marked in millimeters and you can remember that milli- is one thousandth.

[BradWojcikPharmD]

Hi Ksenya, I am a little confused. Is it 10% w/v or 100 g in 100 mL? If it is 10% w/v that is 10%g/mL or 10 g in 100 mL of solution. It is best to go back to the basics and determine how many g of Na salicylate you have in your final solutions, then convert back to percentages. If you withdraw 10 mL of the 10 g/100 mL, you would have 1 g Na Sal in the 10 mL that you withdrew. 10 mL (10 g/100 mL) = 1 g. So you end up with 1 g in 100 mL after you add water up to 100 mL. Now convert back to %.

[BradWojcikPharmD]

Hi Garrett,
Thanks for the nice comment. Yes, once you understand that most of these problems are nothing more than multiplying your given by one or more forms of 1 to change its appearance, the course is pretty easy. Let me know if you have any questions on any specific problems.
-Dr. Brad

[matyuktanya]

Dr. Brad, thank you for the videos for the first time I can somewhat understand the problems. I was wondering if there is a trick to remembering the conversions from mg to g and so on, I realized I need those memorized and I'm having a hard time. Thank you!

[matyuktanya]

Dr Brad,
Thank you that is very helpful, I should be able to learn these and do lots of practicing to get it down. Okay I'll see those links..
Also, a professor told me that in the pharmacy they use conversions for tbsp, oz, gallons and so on.. is that true?

[BradWojcikPharmD]

Hi Matyuktanya,
Yes, you will be doing many different types of conversions. All the conversions are preformed in the same manner, you just have to have the correct conversion factor. You will have to learn that 1 tsp = 5 mL, etc.
Dr. Brad

[CraftyNurseJenn]

Thanks so much for this video! I'm trying to get a head start on a future lecture, and this is exactly what I needed!

[BradWojcikPharmD]

Percent strength for w/v is % g/ mL. You have g/mL now, so to add the %, just multiply by 100%. 1 g/100 mL (100%) = 1% g/mL or 1% w/v. Doing the other problems the same way you will get 2% w/v, 2.5% w/v, 3.5% w/v. Remember, start by calculating how much solute (the Na sal) you will end up with in the final solution, then change back to percent.
Hope this helps and thanks for watching my videos.
-Dr. Brad
p.s if the stock solution was the 100 g/100 mL you calculate the same way and you would have