Acids Lesson 12 Calculating Kbs

You can calculate the Kb using the Ka from the data package page 6 and the equation below.   Ka x Kb = 1.0 x 10-14 @ 25 oC Kb = Kw Ka(conjugate) or Ka = Kw Kb(conjugate)

Calculate the Kb for CN-. Kb(CN-) = Kw Ka(HCN) = 1 x 10-14 4.9 x 10-10 = 2.0 x 10-5

2. Calculate the Kb for K2HPO4. Kb(HPO42-) = Kw Ka(H2PO4-) = 1 x 10-14 6.2 x 10-8 = 1.6 x 10-7

3. Calculate the Kb for K2HC6H5O7. Kb(HC6H5O72-) = Kw Ka(H2C6H5O7-) = 1 x 10-14 1.7 x 10-5 = 5.9 x 10-10

4. 200.0 mL of 0.200 M H2SO4 is mixed with 400.0 mL of 0.250 M NaOH. Calculate the pH of the new solution. H2SO4 + 2NaOH 0.2000 L x 0.200 mole 0.4000 L x 0.250 mole 1 L 1 L I 0.0400 moles 0.100 moles C -0.0400 moles -0.0800 moles E 0 0.020 moles note the loss of 1 sig fig Final volume = 200.0 mL + 400.0 mL = 600.0 mL [NaOH] = 0.020 moles = 0.033 M 0.6000 L pOH = 1.48 pH = 12.52

5. What is the pH of a solution that is amber in neutral red and 5. What is the pH of a solution that is amber in neutral red and yellow in thymol blue? Look at page 7 amber in neutral red pH is 8 or higher yellow in thymol blue pH is 8 or less pH = 8

6. What is the pH of a solution that is blue in Indigo carmine and 6. What is the pH of a solution that is blue in Indigo carmine and thymolphthalein? Look at page 7 blue in indigo carmine pH is 11.4 or less blue in thymolphthalein pH is 10.6 or greater pH = 11

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale For each change 1 unit of pH the [H+] and [OH-] change by a factor of 10 x. This is the nature of the logarithm. 1. If [H+] increases by 100 x

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x the pH increases by 3 3. If [OH-] increases by 100 x

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x the pH increases by 3 3. If [OH-] increases by 100 x

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x the pH increases by 3 3. If [OH-] increases by 100 x the pH increases by 2 4. If [OH-] decreases by 1000 x

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x the pH increases by 3 3. If [OH-] increases by 100 x the pH increases by 2 4. If [OH-] decreases by 1000 x

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x the pH increases by 3 3. If [OH-] increases by 100 x the pH increases by 2 4. If [OH-] decreases by 1000 x the pH decreases by 3 5. If the pH increases by 2 units

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x the pH increases by 3 3. If [OH-] increases by 100 x the pH increases by 2 4. If [OH-] decreases by 1000 x the pH decreases by 3 5. If the pH increases by 2 units the [H+] decreases by 100 x 6. If the pH decreases by 3 units

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x the pH increases by 3 3. If [OH-] increases by 100 x the pH increases by 2 4. If [OH-] decreases by 1000 x the pH decreases by 3 5. If the pH increases by 2 units the [H+] decreases by 100 x 6. If the pH decreases by 3 units

HCl 1 M H+ H2O NaCl OH- NaOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 [H+] pH The pH Scale 1. If [H+] increases by 100 x pH decreases by 2 2. If [H+] decreases by 1000 x the pH increases by 3 3. If [OH-] increases by 100 x the pH increases by 2 4. If [OH-] decreases by 1000 x the pH decreases by 3 5. If the pH increases by 2 units the [H+] decreases by 100 x 6. If the pH decreases by 3 units the [OH-] decreases by 1000 x