[jenniferz3]

I'm trying to figure out "true concentrations" for a lab experiment I just did.
I was trying to find the effect of HCl concentration on beet root permeability. So, what I did was take 5 test tubes, the first with 1ml of HCl, and 4ml of H2O. Then 2ml of HCl, and 3 of H2O and so on until my last test tube was 5ml of HCl. I haven't been in school for a while, so I've forgotten all my basic skills. I thought I could just lable them at 20%, 40% and so on, but my instructer asked me to calculate true concentrations. I'm confused as to how to calculate that.
I used 0.1 M HCl. Do I have to figure out moles? What is the mass?? I've got the molar mass. Which is 36.461g/mol

[UG]

0.1 M HCl is equivalent to 0.1 mol L^-1 HCl. In your first test tube you used 1 mL of HCl. Convert this to litres and multiply by the concentration of HCl, this will give you the number of moles of HCl. You then added 4 mL of water so the total volume is now 5 mL. To find the true concentration of HCl, you then divide number of moles by the volume (check the units are all consistent). See if this helps.

[jenniferz3]

Thank you so much! I was just confusing myself, but that`s perfect! :DD