A diprotic acid has two protons that each have their own Ka values. In a titration with a diprotic acid, we see the following two reactions occurring in sequence:
H2A(aq) + OH-(aq) <--> HA-(aq) + H2O(l)
HA-(aq) + OH-(aq) <--> A2-(aq) + H2O(l)
The sum of these equations is:
H2A(aq) + 2 OH-(aq) <--> A2-(aq) + 2 H2O(l)
Select all of the following that are true:
| HA- is formed by the reaction of base with a diprotic acid |
| If one mole of base is added to one mole of H2A, we will make one mole of A2-(aq) |
| Each of these reactions will have a different Ka. |
| If two moles of base is added to one mole of H2A, we will make essentially two mole of A2-(aq) |
A diprotic acid has two protons that each have their own Ka values. In a titration...
Consider the acid dissociation reactions and for the diprotic acid H2A: H2A(aq) + H2O (l) --><-- HA-(aq) + H3O+(aq) pKa1= 3 H2A(aq) + H2O (l) --><-- A2- (aq) + H3O+(aq) pKa2= 8 Would a salt solution of KHA be acidic, basic or neutral? a) Acidic b) Basic c) Neural
Polyprotic acids contain more than one dissociable proton. Each dissociation step has its own acid-dissociation constant, Ka1, Ka2, etc. For example, a diprotic acid H2A reacts as follows: H2A(aq)+H2O(l)⇌H3O+(aq)+HA−(aq) Ka1=[H3O+][HA−][H2A] HA−(aq)+H2O(l)⇌H3O+(aq)+A2−(aq) Ka2=[H3O+][A2−][HA−] In general, Ka2 = [A2−] for a solution of a weak diprotic acid because [H3O+]≈[HA−]. Many household cleaning products contain oxalic acid, H2C2O4, a diprotic acid with the following dissociation constants: Ka1=5.9×10−2, Ka2=6.4×10−5 Part A) Calculate the equilibrium concentration of H3O+ in a 0.20 M solution of oxalic...
Consider the acid dissociation reactions and for the diprotic acid H2A: H2A(aq) + H2O(1) =HA (aq) + H2O+(aq) pKQ1 = 6 HA (aq) + H20(I) = A2-(aq) + H20+ (aq) pRaz = 10 Would a salt solution of KHA be acidic, basic or neutral? neutral basic O acidic
Strong base is dissolved in 655 mL of 0.600 M weak acid (Ka = 4.06 x 10-5) to make a buffer with a pH of 4.03. Assume that the volume remains constant when the base is added. HA(aq) + OH(aq) > H2O(l) + A (aq) Calculate the pKa value of the acid, and determine the number of moles of acid initially present. pKa = initial amount: mol HA When the reaction is complete, what is the concentration ratio of conjugate...
Strong base is dissolved in 585 mL of 0.600 M weak acid (Ka=3.46×10−5) to make a buffer with a pH of 4.17 Assume that the volume remains constant when the base is added. HA(aq)+OH−(aq)⟶H2O(l)+A−(aq) Calculate the pKa value of the acid, and determine the number of moles of acid initially present. pKa= initial amount: mol HA When the reaction is complete, what is the concentration ratio of conjugate base to acid? [A−]/[HA]= How many moles of strong base were initially...
Strong base is dissolved in 605 mL of 0.200 M weak acid (Ka=4.32×10−5) to make a buffer with a pH of 3.99. Assume that the volume remains constant when the base is added. HA(aq)+OH−(aq)⟶H2O(l)+A−(aq) Calculate the pKa value of the acid, and determine the number of moles of acid initially present. pka = initial amount (mol HA) = A-/HA= how many moles of strong base were initially added? When the reaction is complete, what is the concentration ratio of conjugate...
A diprotic acid, H,A, has acid dissociation constants of Ka molar concentrations of H,A, HA-, and A2- at equilibrium for each of the solutions 1.42 x 10-4 and Ka2 = 4.07 x 1012. Calculate the pH and = A 0.210 M solution of H,A H2A] = pH HA- A2- М М A 0.210 M solution of NaHA HA pH= М
(6) Strong base is dissolved in 555 mL of 0.400 M weak acid (Ka = 3.77 × 10-5) to make a buffer with a pH of 4.05. Assume that the volume remains constant when the base is added. HA(aq)+OH-(aq)=H2O(l)+A-(aq) Calculate the pKa value of the acid and determine the number of moles of acid initially present. When the reaction is complete, what is the concentration ratio of conjugate base to acid? How many moles of strong base were initially added?...
Strong base is dissolved in 765 mL of 0.400 M weak acid (Ka =
4.23 × 10-5) to make a buffer with a pH of 4.19. Assume that the
volume remains constant when the base is added.
Strong base is dissolved in 765 mL of 0.400 M weak acid (Ka 4.23x 10) to make a buffer with a pH of 4.19. Assume that the volume remains constant when the base is added. HA(aq) + OH-(aq) → H2O()-A-(aq) Calculate the pKa...
Titration: Acids and Bases
2. How can you determine which acid is diprotic?
3. using the answers to questions one and two, which acid is
diprotic?
4. Which base has more hydroxide ions per molecule?
Acid Volume Base Base Initial Volume (mL) Base Final Volume (mL) Volume of Base Used (mL) Acid: Base Ratio Acid 1 20 mL Base 1 50 mL 34.5 15.5 4:3 Acid 2 20 mL Base 1 Acid 1 20 mL Base 2 Acid 2 20...