Science Buddies: "Ask an Expert"

Hello Expert.

I am preparing for my Science Project and I am doing the project the Effects of Pollutants on Daphnia. I am having trouble understanding how to dillute the chemical. If I am using 150 ml of the chemical how much water to add to each mixture. I am using weed killer, antifreeze, oil and salt (150 mg).

Please help.

Amirah

Hi Amirah,

It really depends on the concentrations of the chemicals you're using. You have told us that you are adding 150mg of salt (NaCl) to 150mL of water. Based on that information (and using the atomic weight for NaCl, 58.4430g), I can determine that the final molarity of your solution will be 17.1107mM. That means that the rest of your solutions will have to be diluted to this same concentration. I found a great online tool for determining dilutions/molarity http://www.graphpad.com/quickcalcs/Molarityform.cfm . If you need help figuring out how to do the dilutions, you can always repost once you've told us the original concentrations of the solutions you are using. I hope this helps.

Good luck!
Alexis