What is the pH of a buffer solution made from 0.20M HC2H3O2 abd 0.5M C2H302^-.The ionization constant of the acid (Ka)(HC2H3O2)is 1.8multiplied by 10^-5.

(ii)Calculate the ionization constant of its conjugate base

Use the Henderson-Hasselbalch equation to solve part 1.

For part 2, the conjugate base (we'll call the molarity M) is
............A^- + HOH ==> HA + OH^-
initial.....M..............0.....0
change......-x.............x.....x
equil......M-x.............x.....x

Kb for the A^- base = (Kw/Ka for the HA).

To find the pH of a buffer solution, you need to know the concentrations of the acid and its conjugate base, as well as the pKa value of the acid. In this case, we have a buffer solution made from 0.20 M HC2H3O2 (acetic acid) and 0.50 M C2H3O2^- (acetate).

(i) To calculate the pH of the buffer solution, you can use the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

Here, [A-] represents the concentration of the conjugate base (C2H3O2^-), and [HA] represents the concentration of the acid (HC2H3O2). The pKa value for acetic acid is given as 1.8 × 10^-5.

First, calculate the ratio [A-]/[HA]:

[A-]/[HA] = (0.50 M)/(0.20 M)
[A-]/[HA] = 2.5

Next, substitute the values into the Henderson-Hasselbalch equation:

pH = -log(1.8 × 10^-5) + log(2.5)

Using logarithm properties, we can rewrite this as:

pH = log(2.5/1.8 × 10^-5)
pH = log(1.39 × 10^5)

Now, use the logarithm base 10 function on a calculator to find the pH:

pH ≈ 5.14

Therefore, the pH of the buffer solution is approximately 5.14.

(ii) To calculate the ionization constant (Ka) of the conjugate base (C2H3O2^-), you can use the relationship:

Ka × Kb = Kw

Here, Kb represents the ionization constant of the conjugate base and Kw represents the water ionization constant (1.0 × 10^-14 at 25°C).

Rearranging the equation:

Kb = Kw / Ka

Substitute the given value of Ka (1.8 × 10^-5) into the equation:

Kb = (1.0 × 10^-14) / (1.8 × 10^-5)

Now divide the values using the properties of exponents:

Kb ≈ 5.56 × 10^-10

Therefore, the ionization constant (Ka) of the conjugate base (C2H3O2^-) is approximately 5.56 × 10^-10.