when 1.00 g of stearic acid ( a saturated fatty acid) is dissolved in water, then diluted to exctly 10.00 ml, the PH of the resulting solution is 2.73.the fornula weight of steric acid is 284.5. calculate ka and pka for this acid

pH = 2.73 = -log(H^+). Solve for (H^+) and I get something like 1.86E-3 but you need to confirm that. Let HA = fatty acid.

.........HA --> H^+ + A^-
.........x.......0....0
equil....x......1.86E-3..1.86E-3
Ka = (H^+)(A^-)/(HA)
Substitute into Ka expression and solve for x.

To calculate the Ka and pKa for stearic acid (C18H36O2), we need to use the equation for the acid dissociation:

Ka = [H+][A-]/[HA]

where [H+] denotes the concentration of the hydrogen ions, [A-] represents the concentration of the conjugate base, and [HA] symbolizes the concentration of the acid.

First, let's determine the concentration of stearic acid in the solution. We know that 1.00 g of stearic acid was dissolved in water and diluted to exactly 10.00 mL. The molar mass of stearic acid is 284.5 g/mol. We can use this information to convert grams to moles:

moles of stearic acid = mass / molar mass
moles of stearic acid = 1.00 g / 284.5 g/mol
moles of stearic acid = 0.00351 mol

Next, we express the concentration of stearic acid in terms of moles per liter (Molarity):

concentration of stearic acid = moles / volume
concentration of stearic acid = 0.00351 mol / (10.00 mL / 1000 mL/L)
concentration of stearic acid = 0.351 M

Since stearic acid is a monoprotic acid, its concentration will be the same as [HA]. Now, we need to find the concentration of [H+]. To do this, we will use the pH value provided, which is 2.73. The pH is defined as:

pH = -log[H+]

Taking the antilog (10^x) on both sides of the equation, we get:

[H+] = 10^(-pH)
[H+] = 10^(-2.73)
[H+] = 0.000561 M

Now, we can substitute the values into the acid dissociation equation:

Ka = [H+][A-] / [HA]
Ka = (0.000561)^2 / 0.351

Calculating Ka:

Ka = 0.000000315 M

To find pKa, we take the negative logarithm:

pKa = -log(Ka)
pKa = -log(0.000000315)
pKa = 6.50

Therefore, the Ka value for stearic acid is 0.000000315 M, and the pKa value is 6.50.