Chemistry unit conversions help?

JustBeachyNurse, LPN · Sep 7, 2012

What types of conversions are you looking for? When I think chemistry converstions I think Kelvin to degrees Celsius or molecular vs. atomic weight, calculating Molarity (M) , molality (m), and Normality (N) and concentrations by mass, volume, mole fraction. Kind of like this: Calculating Concentration - Concentration Units & Dilutions

Is this for chemistry or pharmacology? (Pharmacology conversions are oz to mL, lb to kg, etc.) if you can give me an example of the type of conversions you are having difficulty with I can possibly point you in the right direction. At one point in my former life I was a biochemistry and molecular biology major....but that's another story. :rolleyes: I did help my sister & her freshman nursing class by tutoring in basic chemistry so they could pass the minimum requirements for her nursing program eons ago (I was a chem dept. major she was a nursing major...)

LaceElaine · Sep 7, 2012

Yes it's for chemistry. A problem that we had in lab last week was something similar to this: Convert .045 J/g°C to kJ/gK. I think that's about right. Hopefully you understand what I mean. My professor wants us to show our work in the form of railroad tracks.

.045 J | 1000 kJ | 2.145 K |

-------------------------------------- = 2.3 kJ/gK

g°C | 1 J | |

Something similar to that. I know the math and setup isn't correct. Some people don't know what railroad tracks are when I ask them so this only serves as an example of the format i have to learn to solve conversions in. Thank you for the help!

meeep, BSN, RN · Sep 8, 2012

I've found that it helps to go one step at a time. What helped me with these types of problems was to always remember to make sure the units cancel. So if you want to cancel out the joules (just an example) make sure one is in the numerator, and the next joules is in the denominator. Half the battle is getting the problem set up correctly. Then it's just simple multiplication/division. You can do it!

JustBeachyNurse, LPN · Sep 8, 2012

If you can wait to later today, I'm on my way out for a CEU class this morning, I know exactly what you are talking about. It's my favorite way of converting units since you cancel units as you go along.

I'm sure I can find you a reference to help you figure this out even if I type one up myself.

Two books that often explain these types of concepts well are "A Cartoon Guide to...." (I've used the one for physics and statistics in the past) and the Dummies Guides. Both series break down difficult concepts into simpler steps.

Here's the chemistry version: http://www.amazon.com/Cartoon-Guide-Chemistry-Larry-Gonick/dp/0060936770. I've not used this version but I've used the physics, calculus and statistics versions and they were a tremendous help!

tikyut · Sep 8, 2012

I would recommend you check out youtube for better explanation on dimensional analysis. It will become second nature to you once you know the basics. you can start with this link

You also have to memorize some key conversions like 1 in = 2.54 cm etc...In that case if you are looking for inch then it would be set up like this 1 in/2.54 cm because you need to cancel out cm.

JustBeachyNurse, LPN · Sep 8, 2012

Try some videos from Khan Academy, there are also videos on basic chemistry and pretty much anything math, science, physics, history and more.

Unit Conversion with Fractions | Ratios and proportions | Khan Academy

Unit Conversion Example: Drug Dosage | Ratios and proportions | Khan Academy

These are their chemistry videos (all are also available on YouTube and as an iPad app (the app you can download videos so you can access them when you lack WiFi access.)

The railroad tracks are basically fractions/proportions. It's a 'long hand' way of making certain that your ratios are correct and it's also a way to easily find an error if your answer is correct. (Remember in grade/high school math where you were required to "show all your work" that was so your teacher could see your thought process and determine where you may have gone right or wrong, and also offer partial credit.)

Do you know the basic unit conversions? Such as 1kg = 2.2 lbs, 1 tsp = 5mL, 1L = 1000 mL, etc.

LaceElaine · Sep 8, 2012

Thanks everyone! I'll try them all! Everything helps. Okay so I understand the part about the same unit has to be in the numerator and then denominator and they have to cancel out until you're only left with what you want it to be converted to. I'm just not understanding how you know unit goes next. I guess this is all memorization? I have a hard time visualizing this all in my head.

JustBeachyNurse, LPN · Sep 8, 2012

Depending on what you are converting, it doesn't always matter the order.

Such as convert ounces (wt) per teaspoon to grams per mililiter

You can do 1oz/2tsp x 1 lb/16 oz x 1 tsp/5mL x 1kg/2.2lb x 1000g/kg and will get the same answer if you do

1oz/2tsp x 1lb/16oz x 1kg/2.2 lb x 1000g/1kg x 1tsp/5mL

LaceElaine · Sep 9, 2012

I didn't know that. Thank you! I'm just going to have to practice practice practice. I get the gist of it. I think I just have to work on memorizing prefixes and units

ksecatero21 · Sep 9, 2012

I felt the same way when I took chemistry this past summer, the way I succeeded in studying the conversion factors were going over them over and over, eventually you'll see a pattern if you're using railroad tiles. but once you get the process it's downhill from there :) good luck!