Lauric Acid Buffer Help!!!

[timtimluuluu]

I am super frustrated.

Ok, so my teacher assigned us a buffer lab in which she gives us the desired pH, acid and salt, and either H20 or Ethyl Alcohol. The buffer that was assigned to me was a buffer consisting of Lauric Acid and Dodecyl sulfate, with the desired pH of 5. kA=5.1E-6.  I thought this would be simple!

Here's my procedure.

The henderson-hasselbach equation to find the ratio.

5 = 5.3 + log(b/a)

And so I got a ratio of .501 moles of the base for everyone 1 mole of acid.

Next, I converted the moles into grams = I think it was about 4 grams of lauric acid and 2.89 grams of dodecyl sulfate after using their molar masses (lauric acid= 200.32, dodecyl sulfate = 288.38).

I measured these out and combined them in a 250 mL beaker. next, I poured about 90 mL of ethyl alcohol because we were to not surpass 100 mL of solution. I'm pretty sure the amount of alcohol doesn't matter as it doesn't change the mole ratio of acid to base.

I put it on the stirring machine with some heat to speed up the dissolution for about 3 minutes. The solution was cloudy and not clear, unlike everyone else's solutions with different combinations of acids and salts. I tested the pH (4.92) which was good enough. However, when 2 drops of HCl were added, the solution's pH plummeted to around 2 :(. I don't know what I did wrong? I tried this three times with different amounts of grams (each with the same mole ratio of course). Please help, every time I fail to create a buffer, I lose 10 points!

[BabcockHall]

it is very unusual to make buffers up in anything but aqueous media.  I don't know what the solubility of lauric acid is in ethanol, but whatever its pK_a in water is, it will have a different pK_{a i ethanol.}