the ka value of 0.001moldm-3 solution of a weak acid is 1.6*10-6 calculate the ph and the pka
........HA ==> H^+ + A^-
I....0.001.....0.....0
C......-x......x.....x
E....0.001-x...x.....x
Substitute the E line into the Ka expression and solve for x = (H^+) and convert to pH. Be careful, you may need to use the quadratic equation; i.e., you may not be able to call 0.001-x just 0.001.
pKa = -log Ka.
To calculate the pH and pKa of a weak acid solution given its Ka value, you can use the following steps:
Step 1: Convert Ka to pKa.
pKa = -log10(Ka)
Given Ka = 1.6 * 10^-6, we can calculate pKa as follows:
pKa = -log10(1.6 * 10^-6)
pKa = -(-6.80)
pKa = 6.80
So, the pKa value is 6.80.
Step 2: Calculate the pH using the pKa value.
pH = 1/2 * (pKa - log10([HA]))
We know that [HA] is the concentration of the weak acid. Given that the concentration of the weak acid is 0.001 mol/dm³, we can substitute these values into the equation to find the pH:
pH = 1/2 * (6.80 - log10(0.001))
pH = 1/2 * (6.80 - (-3))
pH = 1/2 * (6.80 + 3)
pH = 1/2 * (9.80)
pH = 4.9
Therefore, the pH is 4.9.
To calculate the pH and pKa of a weak acid solution based on the value of Ka, you can follow these steps:
Step 1: Convert the Ka value to pKa.
pKa = -log10(Ka)
In this case, pKa = -log10(1.6 x 10^(-6))
pKa = -(-6) = 6
Step 2: Calculate the concentration of H+ ions formed from dissociation.
Since the weak acid is in a 0.001 M solution, the concentration of H+ ions formed will also be 0.001 M.
Step 3: Calculate the pH using the concentration of H+ ions.
pH = -log10([H+])
pH = -log10(0.001)
pH = -(-3) = 3
Therefore, the pH of the solution is 3 and the pKa is 6.