Acids and Bases

pKa

-logKa

pKb

-logKb

pH

-log[H+]

pOH=

-log[OH-]

Kw

1.0 x 10^-14

[H+]

10^-pH

[OH-]

10^-pOH

pH + pOH

14

pKa + pKb =

14

Neutralization reaction

A reaction in which an acid and a base react in an aqueous solution to produce a salt and water

What is a buffer?

A solution that resists changing pH when a small amount of acid or base is added.

Amphoteric

A substance that can act as both an acid and a base

Identify the Lewis acids and bases in the reaction. AlCl3 + H2O <--> (AlCl3OH)- + H+

Acids are H+ and AlCl3 Bases are H2O and (AlCl3OH)-

What is a strong acid?

An acid that ionizes completely in aqueous solution

What is a weak acid?

An acid that partially dissociates .

Salt

An ionic compound made from the neutralization of an acid with a base composed of a cation and anion.

The cation and the anion in a salt

Cation -Doesn't react with water (i.e. Group 1 cations, larger Group 2 cations) -Stronger acid than water (i.e. NH4+, Be2+, Cu2+,Zn2+, Al3+, Cr3+, Fe3+) Anion - Doesn't react with water (i.e. conjugate base of a strong acid) -Stronger base than water (i.e. conjugate base of a weak acid)

Lewis bases

ELectron-pair donors

Lewis acids

Electron-pair acceptors

Strong bases are

Group 1 hydroxides (i.e. NaOH) Group 1 oxides (i.e. Li2O) Some group 2 hydroxides (Ba(OH)2, Sr(OH)2, Ca(OH)2) Metal amides (i.e. NaNH2)

Identify the Bronsted-Lowry acids and bases H2CO3 + H2O <--> H3O+ + HCO3-

H2CO3 and H3O+ are acids H2O and HCO3- are bases

What are the seven strong acids?

HI, HBr, HCl, HClO4, H2SO4, and HNO3

Is the pH of NaCl neutral, acidic, or basic?

Na+ ions are Group 1 ions and do not react w/ water and Cl- is the conjugate base of a strong acid and does not react with water. The pH is neutral.

Bronsted-Lowry base

Proton (H+) acceptor

Bronsted-Lowry Acid

Proton (H+) donor

Is the pH of NH4Cl neutral, acidic, or basic?

The ammonium ion is a stronger acid than water (its the conjugate acid of NH3, a weak base) and Cl- will not react with water.The pH will be less than 7.

As hydrogen ions are added to an alkaline buffer solution, what happens to the concentrations of base and conjugate acid?

The base, B, reacts with the added H+ to form HB+, so the base decreases and the conjugate acid increases.

As hydrogen ions are added to an acidic buffer solution, what happens to the concentrations of undissociated acid and conjugate base?

The conjugate base, A-, reacts with added H+ to form HA, so the conjugate base decreases and the undissociated acid increases.

WHat is an indicator?

Weak acid that undergoes a color change when it's converted to its conjugate base

Orange juice has a pH of 3.5. What is it [H+]?

[H+]= 3.2 * 10^-4 M

If 0.7 mol of benzoic acid (C6H5COOH, Ka= 6.6*10^-5) is added to water to create a 1 L solution, what will be the pH?

[H+]= 7*10^-3 M, pH is ~ 2

Add 0.1 mol of acetic acid (CH3COOH) and 0.1 mol of sodium acetate (NaCH3COO) to water to obtain a 1 L solution. Acetic acid has a Ka= 1.75*10^-5. What is the pH?

[H3O+]= Ka[CH3COOH]/[CH3COO-] [H3O+]= 1.75*10^-5 pH= -log(1.75*10^-5) pH= 4.76

Ka (acid dissociation constant)

[H3O+][A-]/[HA]

Kb (base ionization constant)

[HB+][OH-]/[B]

Given that the self-ionization of water is endothermic, what is the value of the sum pH+pOH at 50C? H2O(l) + H2O(l) <--> H3O+(aq) + OH-(aq) a) Less than 14 b) Equal to 14 c) Greater than 14 d) Cannot determine from the information given

a)

In a 1 M aqueous solution of boric acid (H3BO3, Ka= 5.8*10^-10), which of the following species will be present in solution in the greatest quantity? a) H3BO3 b) H2BO3- c) HBO3 2- d) H3O+

a)

Of the following, which acid has the weakest conjugate base? a) HClO4 b) HCOOH c) H3PO4 d) H2CO3

a)

The pH of a CH3COOH solution is <7 because when this compound is added to water: a) CH3COOH donates H+, making [H+]>[OH-]. b) CH3COOH loses OH-, making [H+]<[OH-]. c) CH3COO- deprotonates H2O, increasing [OH-]. d) CH3COOH dissociation increases [H+], thereby increasing Kw.

a)

A fifty mL solution of HCOOH (formic acid) is titrated with 0.2 M NaOH. The equivalence point is reached when 40 mL of the NaOH solution has been added. What was the original concentration of the formic acid solution?

a*[A]*Va = b*[B]*Vb [A]= b*[B]*Vb/a*Va= (1)(0.2M)(40 mL)/(1)(50 mL)= 0.16 M

pH < 7

acidic

For a weak base titrated with a strong acid, the equivalence point will occur

at pH<7

For a strong acid titrated with a strong base or for a strong base titrated with a strong acid the equivalence point will occur

at pH=7

A 25.0 mL solution of 0.2 M acetic acid (pKa= 4.76) is mixed with 50 mL of 1.0 M sodium acetate (pKb= 9.24). What is the final pH? a) 4.8 b) 5.8 c) 9.2 d) 10.2

b)

List the following compounds by increasing pKa: I. H2SO4 II. NH3 III. CH3CH2COOH IV. HF a) I<III<II<IV b) I<IV<III<II c) III<I<IV<II d) II<III<IV<I

b)

Of the following acids, which one would dissociate to the greatest extent (in water)? a) HCN (hydrocyanic acid), Ka= 6.2*10^-10 b) HNCO (cyanic acid), Ka= 3.3*10^-4 c) HClO (hypochlorous acid), Ka= 2.9*10^-8 d) HBrO (hypobromous acid), Ka= 2.2 * 10^-9

b)

Of the following anions, which is the strongest base? a) I- b) CN- c) NO3- d) Br-

b)

Which of the following salts will produce a basic solution when added to pure water? a) KCl b) NaClO c) NH4Cl d) MgBr2

b)

pH > 7

basic

All of the following are amphoteric EXCEPT: a) HCO3- b) H2PO4- c) SO4 2- d) HOOCCOO-

c)

Of the following liquids, which one contains the lowest concentration of H3O+ ions? a) Lemon juice (pH=2.3) b) Blood (pH=7.4) c) Seawater (pH=8.5) d) Coffee (pH=5.1)

c)

Which of the following compounds could be added to a solution of HCN to create a buffer? a) HNO3 b) CaCl2 c) NaCN d) KOH

c)

Which of the following is an acidic salt? a) KNO3 b) SrCl2 c) CuCl2 d) Ba(CH3COO)2

c)

Which one of the following can behave as a Bronsted-Lowry acid but not a Lewis acid? a) CF4 b) NaAlCl4 c) HF d) Br2

c)

A graph depicting a titration of a weak acid with a strong base will start at a: a) high pH and slope downwards with an equivalence pH equal to 7. b) high pH and slope downwards with an equivalence pH below 7. c) low pH and slope upwards with an equivalence pH equal to 7. d) low pH and slope upwards with an equivalence pH above 7.

d)

Binary mixtures of equal moles of which of the following acid-base combinations will lead to a complete (99+%) neutralization reaction? I. HCl and NaOH II. HF and NH3 III. HNO3 and NaHCO3 a) I only b) I and II only c) II and III only d) I, II, and III

d)

Methyl red is an indicator that changes from red to yellow in the pH range 4.4-6.2. For which of the following titrations would methyl red be useful for indicating the equivalence point? A) HCN titrated with KOH B) NaOH titrated with HI C) C6H5COOH (benzoic acid) titrated with LiOH D) C6H5NH2 (aniline) titrated with HNO3

d)

Of the following, which statement best explains why HF is a weak acid, HCl, HBr, and HI are strong acids? a) F has a greater ionization energy than Cl, Br, or I. b) F has a larger radius than Cl, Br, or I. c) F- has a larger radius than Cl-, Br-, or I-. d) F- has a smaller radius than Cl-, Br-, or I-.

d)

The Ka of HSCN is equal to 1*10^-4. The pH of a HSCN solution: a) will be approximately 4. b) will be approxiately 10. c) will increase as [HSCN] increases. d) cannot be determined from the information given.

d)

What is the conjugate base of HBrO (hypobromous acid)? a) H+ b) H2BrO2 c) H2BrO+ d) BrO-

d)

The conjugate acid of a weak base

is a weak acid.

The conjugate base of a weak acid

is a weak base.

pH = 7

neutral

The conjugate acid of a strong base has

no acidic properties.

The conjugate base of a strong acid has

no basic properties

If 99% of H3O+ ions are removed from a solution whose pH was originally 3, what will be its new pH?

pH 5

Henderson-Hasselbalch equation (for acid)

pH = pKa + log ([conjugate base]/[weak acid])

What is the pH of a solution at 25C whose hydroxide ion concentration is 1*10^-4 M?

pH is 10

For a weak acid titrated with a strong base, the equivalence point will occur at a

pH>7

Henderson-Hasselbalch equation (for base)

pOH = pKb + log [conjugate acid]/[weak base]

The larger the Ka value

stronger acid

Lower Ka value means

the stronger acid.

Lower Kb value means

the stronger the base.

The larger the Kb value

the stronger the base.

The smaller the Kb value

the weaker the base.

The smaller the Ka value

weaker acid

[H+]

y*10^-n pH will be between (n-1)