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Joules23
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Homework Statement
find the pH of:
100mL x .20M HOAc + 100mL x.10M Ba(OH)2
The Attempt at a Solution
100x.2 = 20mmol HOAc
100x.1 = 10mmol Ba(OH)2
20-10=10
10/200=.05M
pOH = -log(.05) = 1.3
pH=14-1.3=12.7
Is this correct?
Joules23 said:Homework Statement
find the pH of:
100mL x .20M HOAc + 100mL x.10M Ba(OH)2
The Attempt at a Solution
100x.2 = 20mmol HOAc
100x.1 = 10mmol Ba(OH)2
20-10=10
10/200=.05M
pOH = -log(.05) = 1.3
pH=14-1.3=12.7
Is this correct?
chemisttree said:Ba(OH)2 is not diprotic. Dibasic.
To calculate the pH of a solution containing both HOAc and Ba(OH)2, you will need to use the Henderson-Hasselbalch equation. This equation is pH = pKa + log([A-]/[HA]), where pKa is the acid dissociation constant of HOAc, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid. You will also need to consider the hydroxide ion concentration from Ba(OH)2 in your calculations.
The pKa value for HOAc, or acetic acid, is 4.76. This value is readily available in chemical reference books or online databases.
You can determine the concentrations of HOAc and Ba(OH)2 by using the molarity (M) formula, which is M = moles of solute/volume of solution in liters. You will need to know the number of moles of each substance present in 100mL of solution in order to calculate their concentrations.
Yes, you can also use the Kw (ionization constant for water) to calculate the pH. The equation is pH = 14 - pOH = 14 - log([OH-]), where [OH-] is the hydroxide ion concentration from Ba(OH)2. However, this method is only accurate if the concentration of HOAc is significantly greater than Ba(OH)2.
The addition of Ba(OH)2, a strong base, will increase the pH of the HOAc solution. This is because the hydroxide ions from Ba(OH)2 will react with the weak acid, HOAc, to form water and the conjugate base, A-. This decreases the concentration of HOAc and increases the concentration of the conjugate base, shifting the equilibrium towards the basic side of the pH scale.