Figuring out Concentration?


by 3riefs
Tags: chemistry, concentraion, molar mass, solution, spectrophotometer
3riefs
3riefs is offline
#1
Apr18-11, 05:40 PM
P: 1
Hello! I'm completing a lab for chemistry and would like some help on the last bit figuring out concentration then converting to molar mass. I need to make a data chart with a line of best fit on it with the dependent/independent variables. I understand that concentration is on the X-axis and the absorption is on the Y-axis. I used a spectrophotometer to track the different absorbency values of the different dilutions we made. I calibrated the machine using a "Blank" which was water in a test tube. I made a test solution, then made different dilutions using a stock solution provided to my class.

The observation chart that was produced looked like:

{Solutions}{Absorbency}{Wavelength (Blue)}

Blank (H2O) 0.00 470nm
Test Sol'n 5g solute/25mL H2O 1.41 470nm
Stock Sol'n 0.83 470nm
0.40 mol/L sol'n 12mL S.S./3mL H2O 0.70 470nm
0.30 mol/L sol'n 9mL S.S./6mL H2O 0.58 470nm
0.20 mol/L sol'n 6mL S.S./9mL H2O 0.40 470nm
0.10 mol/L sol'n 3mL S.S./12mL H2O 0.21 470nm

**Sol'n = solution**
**S.S. = stock solution**
**[ ] = concentration**

1. How do you find concentration?
2. How do you convert concentration to molar mass?
Phys.Org News Partner Science news on Phys.org
Simplicity is key to co-operative robots
Chemical vapor deposition used to grow atomic layer materials on top of each other
Earliest ancestor of land herbivores discovered
Borek
Borek is offline
#2
Apr20-11, 02:51 AM
Admin
Borek's Avatar
P: 22,658
Quote Quote by 3riefs View Post
1. How do you find concentration?
Read it from the line of the best fit. Or, if you use linear regression, calculate concentration from absorbance. That's the same.

2. How do you convert concentration to molar mass?
Knowing concentration you will be able to calculate number of moles, knowing number of moles and mass of the sample you will be able to get molar mass.


Register to reply

Related Discussions
Solution Concentration Biology, Chemistry & Other Homework 1
*urgent* Finding unknown acid concentration Biology, Chemistry & Other Homework 1
Determination of an unknown concentration Biology, Chemistry & Other Homework 5
concentration of a solution Biology, Chemistry & Other Homework 1
solution concentration and ppm Biology, Chemistry & Other Homework 6