K_a x K_b = Kw = 1 x 10^-14 We can calculate Kb for the carbonate ion if we know
ID: 972893 • Letter: K
Question
K_a x K_b = Kw = 1 x 10^-14 We can calculate Kb for the carbonate ion if we know the K_a values for carbonic acid (H_2CO_3) Is K_al or K_a2 of carbonic acid used to calculate the Kb for the carbonate (CO3 / ion? Explain Calculate Kb for the carbonate ion Is the carbonate ion a weaker or stronger base than ammonia? (see table 16-4 for Kb of ammonia) Why? Given that K, for acetic acid is 1 8 x 10'5 and that for hypo chorus acid is 3 x 10'8 Which is the stronger acid? Which is the stronger base?, the acetate ion or the hyp chlorous ion? Calculate Kb values for and CIO'Explanation / Answer
Dear Student,
Question No. 3.
a. Carbonic acid is one of the polyprotic acids: It is diprotic - it has two protons, which may dissociate from the parent molecule. Thus, there are two dissociation constants for carbonic acid.
H2CO3 HCO3 + H+
Ka1 = 4.3 x 10-7
Ka2 = 5.6 x 10-11
Therefore, both Ka values of carbonic acid are considered to calculate Kb.
b To calculate Kb for carbonate ion.
Formula: Ka x Kb = Kw
Kw = 1 x 10-14
Kb1 for carbonate ion = 1 x 10-14 / 4.3 x 10-7 = 2.32 x 10-8
Kb2 for carbonate ion = 1 x 10-14 / 5.6 x 10-11 = 1.78 x 10-4
Therefore, Kb values for carbonate ion are 2.32 x 10-8 and 1.78 x 10-4.
c. The second pKa of carbonic acid is at about 5.6, so the carbonate anion CO32- has a pKb of about 4, which is kind of middling - stronger than ammonia, but much weaker than hydroxide bases.
Therefore, carbonate ion is a stronger base than ammonia.
Question No. 4
Given:
Ka for acetic acid = 1.8 x 10-5
Ka for hypochlorous acid = 3 x 10-8
a. Acetic Acid is a stronger acid because the Ka value of acetic acid is 1.8 x 10-5 and Ka value of hypochlorous acid is 3 x 10-8. A stronger acid will generate more hydronium ions in solution. A larger Ka indicates a greater ratio of ions (including hydronium ions) to uncharged acid. Therefore, a larger Ka indicates a stronger acid.
b. Hypochlorous ion is a strong base. From the table of Ka values acetic acid is a strong acid in compare to the hypochlorous acid. But conversely the conjugate base of acetic acid C2H3O2- is weak base in compare to conjugate base of hypochlorous acid OCl - . Thus the hypochlorite ion OCl - is a stronger base than the acetate ion C2H3O2- .
c. To calculate Kb for acetic acid and hypochlorous acid
Formula: Ka x Kb = Kw
Kw = 1 x 10-14
Kb for acetic acid = 1 x 10-14 / 1.8 x 10-5 = 5.5 x 10-10
Kb for hypochlorous acid = 1 x 10-14 / 3 x 10-8 = 3.3 x 10-7
Therefore, Kb values for acetic acid and hypochlorous acid are 5.5 x 10-10 and 3.3 x 10-7 respectively.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.