CHM 170 Exam #2 Prep example problems and multiple choice

Determine the [OH-] concentration of a 0.116 M Ba(OH)2 solution at 25°C.?

0.116x2=0.232 pOH= -log(0.232) = 0.6345 pH= 14 - 0.6345 pH= 13.36

NH3(aq) + H2O(l) -->

NH4+ (aq) + OH-(aq) Bronsted-Lowry acid-base reaction

Ka=

[H+][A-]/[HA]

ka=

[H+][A-]/[HA]

Kw=[H+][OH-]

Kw=1.0x10^-14

What are some properties of acids?

acids

Optimized buffers have..

base/acid ratio of +-1 around pKa

What are some properties of bases?

bases

In oxyacids, the acid hydrogen atoms are..

bonded to oxygen atoms

What is the pH of a 0.30 M H 2Se solution that has the stepwise dissociation constants K a1 = 1.3 × 10 -4 and

2.20

calculate percent ionization for 0.10 M solution of HC2H3O2 ([H3O+]=1.34x10^-3)?

1.34%

What is the concentration of hydroxide ions in pure water at 30.0 ∘C, if K w at this temperature is 1.47 × 10 -14?

1.47 × 10-7 M, For Pure H2O @ 25 °C ⇒ Kw = 1.0 ⨯ 10-14 [H3O+] = [OH-] = 1.0 ⨯ 10-7

The acid-dissociation constant of hydrocyanic acid (HCN) at 25.0°C is 4.9 × 10 -10. What is the pH of an aqueous solution of 0.090 M sodium cyanide (NaCN)?

11.13

An aqueous solution at 25.0°C contains [H +] = 0.099 M. What is the pH of the solution?

13.0 pOH=-log(0.099) pH=14-1.0

pH+pOH=

14

What is the hydronium ion concentration of a 0.300 M acetic acid solution with K a = 1.8 × 10 -5? The equation for the dissociation of acetic acid is: CH 3CO 2H( aq) + H 2O( l) ⇌ H 3O +( aq) + CH 3CO 2 -( aq)

2.3×10^-3M

What is the pH of a 0.10 M solution of acetic acid (ka=1.8x10^-5)?

2.87

What is the ka of a weak acid if a 0.100 M solution has a pH of 5.25??

3.16x10^-10

Find the percent ionization of a 0.337 M HF solution. The K a for HF is 3.5 × 10 -4.

3.2%

Calculate the ph of a 0.060 m carbonic acid solution, h2co3(aq), that has the stepwise dissociation constants ka1 = 4.3 × 10-7 and ka2 = 5.6 × 10-11.

3.56

Bronsted-Lowry base

A proton acceptor (sink for H+- must contain a lone pair of electrons) (OH-, NH3, SO42-, CO32-)

Bronsted-Lowry acid

A proton donor (source of H+) (HCl, HNO3, H30+, NH4+)

Arrhenius base

A substance that produces OH- ions in aqueous solution (NaOH, KOH, Ba(OH)2)

Identify the strongest acid. HClO2 HClO3 HClO4 HClO Not enough information is given.

As the number of oxygen atom increases, the negative charge dispersal becomes more from Cl atom because of electronegativity of the oxygen atom that increases its acidic strength. Thus HClO4 is the strongest acid among other oxoacids.

Carboxylic acid group

COOH

What are carboxylic acids?

Carboxylic acids have a functional -COOH group and their names end in -anoic acid, (hydrocarbon polyatomic ions)

Problems with Arrhenius definition

Certain compounds and substances, such as NH4, Na2CO3, dissolve in water to form basic solutions, but they do not contain OH- ions, per se.

Nitric acid (HNO3) used in

Fertilizer and explosives manufacturing

Sulfuric acid (H2SO4) used in

Fertilizer and explosives manufacturing, dye and glue production in automobile batteries, electroplating of copper

H+ ions produced by the acid are so reactive they cannot exist alone

H+ ions are technically bare protons

Identify the weakest acid. H2O H2S H2Se H2Te Not enough information is available.

H2O < H2S < H2Se < H2Te.

HNO3 + H2O-->

H30+(aq) + NO3-(aq)

HSO4- + H2O -> H3O+ + SO4(2-)

H3O+ + SO4(2-)

HC2H3O2 + H2O-->>

H3O+(aq) + C2H3O2- (aq)

HCL(g) + H2O(l) -->

H3O+(aq) + Cl-(aq)

Common bases

Household cleaners, baking soda, plaster, soft soaps, laundry detergent, bleach

Carbonic acid (H2CO3)

In carbonated beverages from reaction of carbon dioxide and water

Citric acid (H3C6H5O7)

In citrus fruits such as lemons and limes, used to adjust pH in foods and beverages

Which one of the following salts, when dissolved in water, produces the solution with the highest pH? KI KF KBr KCl

KF because it is very electronegative

Which one of the following will form an acidic solution in water? NH4Cl KBr NaI LiNO3 None of the above solutions will be acidic.

NH4Cl, When Ammonium chloride is dissolved in water Ammonium ions and Chloride ions are formed. Ammonium ion is a strong conjugate acid of the weak base of Ammonia whereas chloride ion is a weak conjugate base of the strong Hydrochloric acid. The solution of Ammonium Chloride is therefore acidic.

Which one of the following salts, when 1 mole is dissolved in water, produces the solution with a pH closest to 7.00? NaOH NH4Br NaI NaF Ca O

NaOH

What is the pH of a 0.10M solution of chlorous acid (ka=1.1x10^-2)?

Need to know when to use quadratic formula

Arrhenius acid

Produces H+ ions when dissolved in aqueous solution (HCl, HNO3, H2SO4, HC2H3O2)

Amphoteric substances

Substances that can react as both acids and bases

Weak acids described by

equilibriu

Phosphoric Acid (H3PO4) used in

fertilizer, beverage preservation

What do oxyacids contain?

hydrogen and an oxyanion, (oxygen-rich polyatomic ion)

Acids ionize in water to produce H+...

ions and anions

Bases dissociate in water to produce OH-...

ions and cations

A solution is prepared by dissolving 0.25 mol of lactic acid and 0.23 mol of sodium lactate in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of NaOH to this buffer solution causes the pH to increase slightly. The pH does not increase drastically because the NaOH reacts with the ________ present in the buffer solution. The K a of lactic acid is 1.4 × 10 -4.

lactic acid

Hydrochloric acid (HCL) used in

metal cleaning, food preparation, ore refining, stomach acid

Hydrofluoric acid (HF) used in

metal cleaning, glass frosting

If an acid has more than one hydrogen atom...

not all may be acidic

[H30+]=3.4x10^-4--> pOH?

pH=-log(3.4xx10^-4)=3.47-->pOH=14.00-3.47 = 10.53

What is the pH of a 0.300 M NH 3 solution that has K b = 1.8 × 10 -5? The equation for the dissociation of NH 3 is: NH 3( aq) + H 2O( l) ⇌ NH 4 +( aq) + OH -( aq)

pH=11.37

What is the pOH equation?

pOH=-log[OH-]

Acetic acid (H3C6H5O7) used in

plastic and rubber manufacturing, food preservation, active component of vinegar

Autoionization of water

pure water reacts with itself to form hydronium and hydroxide ions

pH involved in calculations is read by..

sig digits

Strong acids are

strong electrolytes

Typically, ignore contributions from anything but the strongest acid.

study

Percent ionization

the concentration of ionized acid in a solution divided by the initial concentration of acid multiplied by 100%

percent ionization

the concentration of ionized acid in a solution divided by the initial concentration of acid multiplied by 100%

A binary acids has...

two atoms. Example: HCL (hydrochlocic)

weak acids are

weak electrolytes

What is a monoprotic acid?

~ Donates one proton when dissociating in aqueous solutions