Equilibrium and Acids and Bases Part 2

Why is H2SO4 strong acid special? What is the pH of 0.01M H2SO4?

-It is Diprotic. Has 2 Hydrogens -Can donate more than one Hydrogen. -First H dissociates completely, the second is weak (so dissociates a little) [H+]≅0.01M (it's a little bit more since more H is dissociated from the weak second H) pH≅2 (but is a little bit less since more H is dissociated from the weak second H, like 1.98)

Who were the three different people who developed Acid and Base definitions?

1. Arrhenious 2. Bronsted-Lowry 3. Lewis

What is the conjugate base of OH-?

O 2- It is amphoteric or amphiprotic (can be both acid or base)

Heat+H20(l)↔ H+(aq) + OH-(aq) but @ 37°C. What is the pH?

@ 37°C favors endothermic reaction so shifts to the products. By increasing products, Kw will be bigger. So let us say Kw=1.0x10^-13 [H+]=[OH-]=1x10^-6.5 pH=pOH=6.5

What is the trend of acidity with pKa?

Acid strength increases as pKa decreases

What are the two rules of ranking Oxoacids? Do Oxoacids follow binary acid rules?

1) More oxygens, more acidic e.g. HClO3 > HClO2 2) More electronegative heteroatom, more acidic. (not O or H) e.g. HClO3 > HBrO3 (even though Br is bigger than Cl) ****Binary acid rule does not apply for oxoacids

What is the Lewis Acid and Base?

Acid= Electron acceptor Base= Electron donor BF3 and Metal ions only good Lewis acids

What is the Bronsted-Lowry Acid and Base?

Acid= H+ donor Base= H+ acceptor

What is the Arrhenious Acid and Base?

Acid= H+(proton) donor in H2O Base= OH- donor in H2O

Why can you solve for the first and not the second question? What is the pH of 0.01 M HCl? What is the pH of 0.1 M HC2H3O2?

HCl is a strong acid so we know it dissociates completely in water. [H+]=0.01M→pH=2 HC2H3O2 is a weak acid and we don't know how it dissociates. ***We need the Ka value to solve.

What are strong acids you should know?

HClO4, H2SO4, HI, HBr, HCl, HNO3, HClO3

Which is the strongest acid? Why? CH4 NH3 H2O HF

HF is most acidic (but still a weak acid) -electronegativity (side to side) -The more polar bond makes the element more acidic.

Which is the strongest acid? Why? HF HCl HBr HI

HI -Size(up to down) -Bond between H and I is longest because I size is greatest -So it is the strongest acid because dissociates the easiest. HF is a weak acid

What is the Binary Acid trend? What can it help you do?

Helps you rank what is more acidic

If the pH is 4.9, what is the [OH-] of the solution? 6.9x10-9M 8.6x10-8M 1.6x10-10M 7.9x10-10M

If the pH = 4.9, then the pOH = 9.1 [OH-] = 10-pOH = 10-9.1 which will be between 1.0x10-10M and 1.0x10-9M which still leaves us with 2 possible answer choices (1.6x10-10M and 7.9x10-10M) so well have to be more precise. Youll have to remember not only the [OH-] values when the pOH is an integer but also for the halves (.5) too. The half pOH occurs when [OH-] = 3.16x10-whatever as demonstrated below: [OH-] = 1x10-9M pOH = 9 [OH-] = 3.16x10-10M pOH = 9.5 [OH-] = 1x10-10M pOH = 10 Since a pOH of 9.1 is between 9 and 9.5, the [OH-] must be between 3.16x10-10M and 1x10-9M and therefore 7.9x10-10M must be the correct answer.

How to solve for pH, pOH, [H+], [OH-]

If you know 1 of the 4, you can calculate the other 3. pH=-log[H+] [H+]=10^-pH pOH=-log[OH-] [OH-]=10^-pOH pH+pOH=14 [H+][OH-]=1x10^14

What is the pH of 0.01 M NaOH? What is the pH of 0.01 M Ba(OH)2?

NaOH is a strong base: [OH-]=.01M →pOH=2 →pH=12 Ba(OH)2 is a strong base. For these metal hydroxides, both hydroxides dissociate completely (***so double hydroxide amount) [OH-]=0.02M →pOH=1.7 →pH=12.3

Which of the following has the strongest conjugate base? NH4+(Ka=5.6x10^-10) HCO2H (Ka=1.8x10^-4) HCN (Ka=4.9x10^-10) HF (Ka=6.8x10^-4)

Strongest conjugate base means a weak acid. Weak acid has the lowest Ka value. HCN (Ka=4.9x10^-10)

If the pH is 6.6, what is the [H+] of the solution? 2.5x10-7M 6.6x10-7M 3.1x10-8M 7.4x10-6M

[H+] = 10^-pH = 10^-6.6 which will be between 1.0x10-7M and 1.0x10-6M which still leaves us with 2 possible answer choices (2.5x10-7M and 6.6x10-7M) so well have to be more precise. Youll have to remember not only the [H+] values when the pH is an integer but also for the halves (.5) too. The half pH occurs when [H+] = 3.16x10-whatever as demonstrated below: [H+] = 1x10-6M pH = 6 [H+] = 3.16x10-7M pH = 6.5 [H+] = 1x10-7M pH = 7 Since a pH of 6.6 is between 6.5 and 7, the [H+] must be between 1x10-7M and 3.16x10-7M and therefore 2.5x10-7M must be the correct answer.

What is the pH of .1M HC2H3O2? Ka=1.75x10^-5

[H+]= sqrt( (1.75x10^-5) [.1]) [H+]= sqrt(1.75x10^-6) [H+]= 1.3x10^-3 →pH= 2.9

What equation do you use to solve for pH for weak acids?

[H+]=sqrt( (Ka) [HA] )

What is the pH of 0.01M HOCl (Ka = 2.9x10^-8)? 2.0 2.8 4.8 7.5

[H+]=sqrt(2.9x10^-8)[.01]) = 1.7x10^-5 pH = -log [H+]= -log(1.7x10-5) = 4.8

What is the pH of 10M CsOH?

[OH-]=10M →pOH=-1 → pH=15 This is possible! You can run into pH in negatives or above 14.

What is the pH of 0.1M NaF (Kb,F-=1.5x10^-11)? 8.1 7.8 6.1 5.9

[OH-]=sqrt( (1.5x10^-11)[.1]) =1.2x10^-6 M pOH=-log[OH-]=-log(1.2x10^-6)~5.9 pH=14-pOH=14-5.9=8.1

What is the pH of 0.01M C5H5N (Kb = 1.5x10^-9)? 9.0 8.6 11.2 12.2

[OH-]=sqrt( (1.5x10^-9)[.01]) = sqrt(15x10^-12) = 3.9x10^-6 pOH = -log[OH-] = -log(3.9x10^-6) = 5.4 pH = 14 pOH = 14 5.4 = 8.6

What equation do you use to solve for pH for weak bases?

[OH-]=sqrt( (Kb) [A-] )

If [H+] = 4.0x10^-3M, what is the pH of the solution? 2.9 2.4 3.1 1.9

pH = -log (4.0x10-3) which should be between 2 and 3. As [H+] increases, pH decreases (theyre inversely related). Since the -log of 1x10^-3 = 3, then the -log of a slightly higher [H+] will yield a slightly lower pH. But this still leaves us with two possible correct answer choices (2.4 and 2.9) and so youll have to remember not only the [H+] values when the pH is an integer but also for the halves (.5) too. The half pH occurs when [H+] = 3.16x10-whatever as demonstrated below: [H+] = 1x10^-2M pH = 2 [H+] = 3.16x10^-3M pH = 2.5 [H+] = 1x10^-3M pH = 3 Since 4.0x10^-3 is between 3.16x10^-3 and 1x10^-2, then the corresponding pH will be between 2.5 and 2 making 2.4 the correct answer in this case.

If [H+] = 6.4x10-8M, what is the pH of the solution? 6.8 8.3 7.2 7.8

pH = -log [H+] pH = -log (6.4x10-8) which should be between 7 and 8. As [H+] increases, pH decreases (theyre inversely related). Since the -log of 1x10^-8 = 8, then the -log of a slightly higher [H+] will yield a slightly lower pH. But this still leaves us with two possible correct answer choices (7.2 and 7.8) and so youll have to remember not only the [H+] values when the pH is an integer but also for the halves (.5) too. The half pH occurs when [H+] = 3.16x10^-whatever as demonstrated below: [H+] = 1x10^-7M pH = 7 [H+] = 3.16x10^-8M pH = 7.5 [H+] = 1x10^-8M pH = 8 Since 6.4x10^-8 is between 3.16x10^-8 and 1x10^-7, then the corresponding pH will be between 7.5 and 7 making 7.2 the correct answer in this case.

If [OH-] = 6.0 x 10^-10M, what is the pH of the solution? 4.1 4.8 5.2 8.8

pOH = -log (6.0x10-10) which should therefore be between 9 and 10 and so the pH should be between 4 and 5 which still leaves us with 2 possible answer choices (4.1 and 4.8) so well have to be more precise. [OH-] = 1x10-9M pOH = 9 [OH-] = 3.16x10-10M pOH = 9.5 [OH-] = 1x10-10M pOH = 10 Since 6.0 x 10-10M is between 3.16x10-10M and 1x10-9M, then the corresponding pOH will be between 9.5 and 9. Subtracting from 14 reveals that the pH must be between 4.5 and 5 and so 4.8 must be the correct answer.

What is the trend of acidity with Ka?

The strongest acid is the one that dissociates the most which is the one with the highest Ka value

What is Kw represent? What equations do you use to solve for Kw?

Water dissociating into ions in water. H2O(l) ↔ H+(aq) + OH-(aq) Kw=[H+][OH-]=1.0x10^-14 *****@ 25°C Ka * Kb = Kw pKa + pKb = 14

Which of the following solutions is most basic? Pure water pOH=12 0.001M NH3 [H+]=1.0x10-11M

Water pH=7 pOH=12 : pH=2 If NH3 were a strong base it would dissociate completely yielding [OH-] = 0.001M and so pOH = -log (0.001) = 3 and pH = 11. Since its a weak base we know the pH will be <11. [H+] = 1.0x10-11M so pH = -log (1.0x10-11M) = 11 which is the most basic of the choices.

Which of the following is the strongest acid? H2O H2S H2Se H2Te

For binary acids, acid strength increases down the periodic table with increasing size (as a larger anion is a more stable conjugate base). H2Te

What are strong bases you should know?

Group 1 metal hydroxides(OH), Ba(OH)2, Sr(OH)2, Ca(OH)2

If the pH is 3.2, what is the [H+] of the solution? 2.1x10-3M 8.9x10-3M 6.3x10-4M 8.9x10-5M

H+] = 10-pH = 10-3.2 which will be between 1.0x10^-4M and 1.0x10^-3M The only answer choice in this range is 6.3x10-4M which therefore must be the correct answer.

What else can be used instead of just a proton(H+)?

H30+ can be interchangeable with H+

What is the conjugate base of HCO3-? What is the conjugate acid of HCO3-?

Looking for conjugate base, so HCO3- acts like an acid. CO3 2- It is amphoteric or amphiprotic (can be both acid or base) Conjugate acid= H2CO3

What does Ka represent?

Dissociation of weak acid in water. HA(aq) ↔H+(aq) + A-(aq) HA=weak acid or HA(aq) + H20 ↔H30+(aq) + A-(aq)

What does Kb represent?

Dissociation of weak base in water A-(aq) + H2O(l) ↔ HA(aq)+ OH-(aq) A-=Weak base