- #1

uzi

- 1

- 0

pKa = 8.3

so far this is what i have:

I need 8.49 g of Tris HCL because:

...(o.7M)*0.1L *(121.4g/mol)

THIS part of the calculation is right so dont worry about it. however i cant get the ratios right.

pH = pKa + log (base/acid)

7.9=8.3 + log (Trisb/Trisa)

7.9-8.3 = log (Tb/Ta)

-04 = log (Tb/Ta)

antilog -0.4 = 0.4

There are 4parts acid to 1 part base therefore:

Tb = 0.4Ta

Total tris = 0.70M

ThereforeL 0.7M =Tb +Ta

0.7 = 0.4Ta + Ta

0.7 = 0.4(4 parts Ta) + 0.4

0.7 = 2Ta

hence:

Ta = 0.7M/2 = 035

Tb = 0.70M - 0.35 = 0.35

BUT this doesnt make sense, cuz if youplug the ratios into the HH equation you dont get the right pH:

pH = 8.3 + log (0.35/0.35)

pH = 8.3 + 0

pH = 8.3

I need to make it a pH of 7.9 !!!!!!!!

and then on top of that since the ratios are wrong I cant successfully calculate the HCL volume. T.T

The only correct ratios that would make sense are .2 and .5, but I did that through trial and error therefore I cannot use it.

pH = 8.3 + log (0.2/0.5)

pH = 8.3 + (-0.397)

pH = 7.9