Acids and Bases Lactic acid is one of many metabolities produced - - PDF document
Slide 1 / 123 Slide 2 / 123 Chemistry Atomic Origins 2015-08-14 www.njctl.org Slide 3 / 123 Acids and Bases Lactic acid is one of many metabolities produced when we exercise. It generally loses an H+ ion to from the lactate ion (one of
2015-08-14 www.njctl.org
lactic acid lactate Lactic acid is one of many metabolities produced when we exercise. It generally loses an H+ ion to from the lactate ion (one of the chemicals that causes burning sensations in
In any sample of water, a small number of water molecules will dissociate into H+ and OH- ions.
H H O O H H +
The H+ ion then typically binds to a lone pair of electrons on another water molecule to make the hydronium ion: H3O+ 2H2O(l) -------> OH-(aq) + H3O+(aq)
H H O O H H
H H O H H O
In 1909, a device was invented that could measure the H+ or H3O + concentration in an aqueous solution.
H3O+(aq) = 1.0 x 10 -7 M @ 25 C
Using this data, the equilibrium constant for the auto-ionization of water can be calculated. 2H2O(l) --> H3O+(aq) + OH-(aq) Recalling our equilibrium concepts...... Kw = [H3O+][OH-] Since equal amounts of H3O+ and OH- are created... [H3O+] = [OH-] = 1.0 x 10 -7 M Kw = (1.0 x 10 -7)(1.0 x 10 -7) = 1.0 x 10 -14 M
Clearly, the equilibrium lies far to the left! Water does NOT like to dissociate.
1
What is the concentration of hydronium ions (H3O+) in pure water?
A 1.0 x 10 -2 M B 1.0 x 10-5 M C 1.0 x 10-7 M D 1.0 x 10 -10 M E 1.0 x 10-14 M
answer
2
Which of the following is the value of Kw for water?
A 1.0 x 10-2 B 1.0 x 10-4 C 1.0 x 10-7 D 1.0 x 10-9 E 1.0 x 10-14
answer
3
Which of the following would be true in pure water?
A [H3O+] = [OH-] B [H3O+] < [OH-] C [OH-] = 1 x10-7 M D A and C E B and C
answer
4 The magnitude of K w indicates that _________
A water ionizes to a very small extent B the autoionization of water is exothermic C water ionizes very quickly D water ionizes very slowly
answer
5 The molar concentration of hydronium ion,
[H3O+], in pure water at 25 °C is ___________.
1
answer
In the natural world, we do not find pure water. There are always things dissolved in it that influence the concentrations of hydronium and hydroxide ions. The hydronium or hydroxide concentration in a solution can be determined easily if one knows one or the other. Kw = [H3O+][OH-] = 1.0 x 10-14 Rearranged for [H3O+] Rearranged for [OH-] [H3O+] = 1.0 x 10-14/[OH-] [OH-] = 1.0 x 10-14/[H3O+]
Kw = [H3O+][OH-] rearranged to find [OH-] = Kw/[H3O+] = 1.0 x 10-14/ 3.4 x 10-5 = 2.9 x 10-10 = [OH-] Kw = [H3O+][OH-] rearranged to find [H3O+] = Kw/[OH-] = 1.0 x 10-14/ 1.2 x 10-12 = 8.3 x 10-3 = [H3O+] #1 What is the [OH-] in a solution with [H3O+] = 3.4 x 10-5 M? #2 What is the [H3O+] in a solution with [OH-] = 1.2 x 10-12
Let's do some examples! move for answer move for answer
Application: Tap water is NOT pure water. There are many things dissolved in it that affect the amount of [H3O+] and [OH-] in the water sample. Can you think of some things that might chloride (Cl-), carbonate (CO32-) be dissolved in tap water? Flouride (F-), calcium ions (Ca2+), c The average concentration of H3O+ in New York City tap water is 5.01 x 10-8 M. What is the average [OH-]? Kw = [H3O+][OH-] rearranged to find [OH-] = Kw/[H3O+] = 1.0 x 10-14/5.01x 10-8 = 1.99x 10-7 M
move for answer
6 What is the [H3O+] in an aqueous sample with an
[OH-] equal to 3.4 x 10-3 M?
A 3.4 x 10-3 M B 2.9 x 10-12 M C 1.0 x 10-7 M D 9.4 x 10-7 M E 3.4 x 1011 M
answer
7 Which of the following would have the smallest
[OH-]?
A solution with [H3O+] = 2.4 x 10-1 B solution with [H3O+] = 2.4 x 10-11 C solution with [H3O+] = 2.4 x 10-6 D solution with [OH-] = 2.4 x 10-3 E solution with [OH-] = 2.4 x 10-12
answer
8 The pacific ocean off the coast of Hawaii has
a [OH-] = 8.32 x 10-9 M. What is the [H3O+]?
answer
As we have learned, when certain substances are added to water, the H
3O+ concentration changes.
Furthermore, if the [H3O+] changes, it would influence the [OH-]. Kw = [H3O+] [OH-] = 1.0x 10-14
In 1884, Swedish scientist Svante Arrhenius decided to create definitions for substances that changed the [H3O+] in an aqueous solution.
Arrhenius labeled anything that increased the [H3O+] an acid Arrhenius labeled anything that increased the [OH-] a base By measuring the [H3O+] of a water solution after a substance had been added, he could see if the substance was acidic or basic!
H3O+(aq) = 2.3x 10-6 M @ 25 C
HCN(aq) Example 1: Let's add some HCN(aq) Remember that pure water has an [H3O+] = 1.0 X 10-7M. Since the [H3O+] is higher than 1.0 X 10-7M, Arrhenius would have described HCN as an acid!
By measuring the [H3O+] of a water solution after a substance had been added, he could see if the substance was acidic or basic!
H3O+(aq) = 4.1x10-11 M @ 25 C
NaOH(s) Example 2: Let's add some NaOH(s) Since the [H3O+] is lower than 1.0 x 10-7 M thereby making the [OH-] higher than 1.0 x 10-7M, Arrhenius would have described NaOH as a base!
9 Which of the following solutions would be
considered by Arrhenius to be the most basic?
A 0.1 M NH3 [H3O+] = 3.4x10-10 M B 0.1 M NaOH [H3O+]= 1x10-13M C 0.1 M HCl [H3O+] =1x10-1 M D 0.1 M HCN [H3O+]= 2.3x10-6M E Pure water [H3O+]=1x10-7 M
answer
10 Vinegar has a [H3O+] of around 3.4 x10-3 M. Which of
the following solutions would be considered by Arrhenius to be MORE acidic than vinegar?
A 0.1 M NaOH [H3O+] = 1x10-13 M B 0.1 M HCl [OH-] =1.0 x10-13 M C 0.1 M NaCN [OH-] = 2.6x10-4 M D 0.1 M NH3 [H3O+] = 7.6x10-9 M E pure water [OH-] = 1.0 x10-7 M
answer
At this time, most scientists explained Arrhenius acids as possessing H+ ions that could be added to water to produce [H3O+] Arrhenius acids in action HF(aq) + H2O(l) --> F-(aq) + H3O+(aq) Here, the hydroflouric acid (HF) donates one of it's H+ ions to a water molecule increasing the [H3O+](aq) Two scientists - Bronsted and Lowry, working independently, decided a more appropriate definition of an acid would be that of an H+ donor.
At this time, most scientists explained Arrhenius bases as possessing OH- ions that would increase the [OH-] and decrease the [H3O+]. NaOH(aq) --> Na+(aq) + OH-(aq) [OH-] causes [H3O+] Arrhenius base in action Unfortunately, this view required that all bases had to possess the hydroxide ion. This was clearly not the case. Many substances, like ammonia (NH3) or sodium phosphate (Na3PO4), were known to be basic but did NOT have any hydroxide ions!
Bronsted and Lowry proposed that, insteading of possessing hydroxide ions, a base was a substance that accepted an H+ from water to produce OH- ions! NH3(g) + H2O(l) --> NH4+(aq) + OH-(aq) Bronsted base in action When ammonia, NH3, accepts the H+ from the water, the water turns into OH- making the solution basic.
Summary Acids are defined as H+ (proton) donors. HC3H6O3(aq) + H2O(l) --> C3H6O3-(aq) + H3O+(aq)
lactic acid
cyanide base
Bases are defined as H+ (proton) acceptors. CN-(aq) + H2O(l) --> HCN(aq) + OH-(aq)
11 A Bronsted acid is a substance that...
A accepts H+ ions B donates OH- ions C increases the concentration of OH- ions D donates H+ ions E accepts OH- ions
answer
12 Which of the following could NOT act as a Bronsted
acid?
A HCN B H2SO4 C NH4+ D H3O+ E BF3
answer
13 A Bronsted-Lowry base is defined as a
substance that __________.
A increases [H+] when placed in H2O B decreases [H+] when placed in H2O C increases [OH-] when placed in H2O D acts as a proton acceptor E acts as a proton donor
answer
14 Which of the following compounds could never
act as a Bronsted acid?
A SO4 2- B HSO4 - C H2SO4 D NH3 E CH3COOH
answer
Acids and Bases go together It should be noted that if an acid donates an H+, that H+ will be accepted by another substance. So, where there is an acid, there will be a base N H H H O H H N H H H H O H + + NH3 acts as a base and accepts an H+ to become NH4+ water acts an acid and donates it's H+ to become OH-
Identifying an acid or a base By examining the products and reactants of a chemical reaction,
base. Example HSO4-(aq) + CN-(aq) --> SO4 2- (aq) + HCN(aq) HSO4-(aq) donated an H+ to become SO4 2- = It's an acid! CN-(aq) accepted an H+ to become HCN = It's a base!
Identifying an acid or a base Identify which reactant behaves as an acid and which behaves as a base in the following reaction! H2O(l) + CH3NH3 +(aq) --> CH3NH2(aq) + H3O+(aq) CH3NH3 +(aq) donated an H+ to become CH3NH2 = It's an acid! H2O(aq) accepted an H+ to become H3O+ = It's a base! move for answer
15 According to the following reaction, which
reactant molecule is acting as an acid?
A H2SO4 B H2O C H3O+ D HSO4 - E None of the above
H2O + H2SO4 → H3O+ + HSO4 -
answer
16 According to the following reaction, which
reactant molecule is acting as a base? H2O + H2SO4 → H3O+ + HSO4 -
A H2SO4 B H2O C H3O+ D HSO4 - E None of the above
answer
17 According to the following reaction, which reactant
molecule is acting as a base? H3O+ + HSO4 - → H2O + H2SO4
A H2SO4 B H2O C H3O+ D HSO4 - E None of the above
answer
18 For the following reaction, identify whether the
circled compound is behaving as an acid or a base.
A Acid B Base C Neither D Both E None of the above
H3PO4 + H2O ⇌ H2PO4 - + H3O+
answer
19 For the following reaction, identify whether the
circled compound is behaving as an acid or a base. H3PO4 + H2O ⇌ H2PO4 - + H3O+
A Acid B Base C Neither D Both E None of the above
answer
Identifying an acid or a base in reversible reactions Reactions are reversible so we must be able to identify acids and bases based on the reverse reaction. Example F-(aq) + H2O(l) <--> HF(aq) + OH-(aq) HF(aq) donates an H+ ion to become F-(aq) = It's an acid OH-(aq) accepts an H+ to become H2O(l) = It's a base
20 For the following reaction, identify whether the
circled compound is behaving as an acid or a base. H3PO4 + H2O ⇌ H2PO4 - + H3O+
A Acid B Base C Neither D Both E None of the above
answer
21 For the following reaction, identify whether the
circled compound is behaving as an acid or a base. H3PO4 + H2O ⇌ H2PO4 - + H3O+
A Acid B Base C Neither D Both E None of the above
answer
The term conjugate comes from the Latin word “conjugare,” meaning “to join together.” Reactions between acids and bases always yield their conjugate bases and acids.
HNO2(aq) + H
2O(l) NO 2 - (aq) + H 3O+(aq)
donates H
+
accepts H+ Acid Base Conjugate base conjugate acid
To find an acid or bases conjugate in a reaction, simply write the formula for the substance left after the H+ has been donated or accepted. Example: What is the conjugate base of HSO4 -(aq)? Since we are looking for a conjugate base, HSO4 - must be an acid so let's have it donate an H+ HSO4 -(aq) --> SO4 2- (aq) + H+(aq) conjugate base
Example: What is the conjugate acid of CO3 2- (aq)? Since we are looking for a conjugate acid, CO3 2- must be a base so let's have it accept an H+ CO3 2- (aq) + H+ --> HCO3 -(aq) conjugate acid Dealing with charges If you accept an H+, you become more positive If you donate an H+, you become more negative
22 Which of the following would be the conjugate
base of HNO2?
A NO2 - B H2NO2 C NO2 D NO2 2- E HNO2
answer
23 Which would be the conjugate acid of HCO3 -(aq)?
A CO3 2- B HCO3 C CO3 D H2CO3 - E H2CO3
answer
24 What would be the an acid/conjugate pair in the
following reaction?
A NH2-/H2O B NH2-/NH3 C H2O/OH- D H2O/NH3 E None of these NH2 - + H2O --> NH3 + OH-
answer
Definition Scientists noticed that some substances could create acidic solutions despite not having any H+ ions to donate. An example of this was the Ca2+ ion. G.N. Lewis proposed a mechanism for this Ca2+ + ---> Ca (OH)+ + + O H H H The metal ion accepted a pair of electrons from the water molecule, resulting in the donation of one of the water's H+ ions.
A Lewis acid is an electron pair acceptor. Metal ions or molecules with incomplete octets (BF3) are good examples. A Lewis base is an electron pair donor. Molecules with unbonded electrons (NH3, CN-, OH-, H2O) are good examples. Lewis Acid (e- pair acceptor) Lewis Base (e- pair donor)
25 A lewis base is a substance that...
A Accepts H+ ions B Donates H+ ions C Accepts e- pairs D Donates e- pairs E Decreases the concentration of [OH-]
answer
26 Which of the following would likely act as a lewis
acid?
A NH3 B OH- C CN- D H2O E Fe3+
answer
Definition Type Acid Base
Arrhenius (traditional) substance that produces H3O+ ions in aqueous solution substance that decreases H3O+ ions in aqueous solution Bronsted -Lowry substance that donates H+ ions in reaction substance that accepts H+ ions in reaction Lewis substance that accepts an electron pair in reaction substance that donates an electron pair in reaction
Question 1: Can you think why the Arrhenius definition was considered insuffienct? It could not explain how a substance without hydroxide could make a solution basic Question 2: Can you explain why Lewis felt that the Bronsted definition was insufficient? It required an acid to be in possession of a hydrogen atom. move for answer move for answer
All acids are Lewis acids, most are also Bronsted acids, and many are Arrhenius acids Lewis Bronsted Arrhenius The lewis definition is generally considered the most broad.
If a substance can act both as an acid and base, it is known as
depending on the situation.
HCl + H2O Cl- + H3O+
Above, water accepts a proton, thus acting as a base.
NH3 +H2O NH4 + + OH-
Above, water donates a proton, thus acting as an acid
Because of water's amphoteric nature, it makes the perfect solvent for most acid base reactions. Its nature allows for easier exchange of protons between acids and bases.
Strong acids are completely ionized in water (They all donate their H+ ions). Their conjugate bases are very weak.
Strong W e a k Negligible S t r
g W e a k Negligible
Acid Base HCl Cl - H2SO4 HSO 4- HNO3 NO 3- H3O+ H 2O HSO4- SO 42- H3PO4 H2PO4- HF F- HC2H3O2 C2H3O2- H2CO3 HCO 3- H2S HS - H2PO4- HPO 42- NH4+ NH 3 HCO3- CO 32- HPO42- PO 43- H2O OH - OH- O 2- H2 H - CH4 CH 3- 100% protonated in H
2O
Base strength increases Acid strength increases 100% ionized in H
2O
Weak acids only ionize partially in water. Their conjugate bases are weak bases.
S t r
g W e a k Negligible S t r
g W e a k Negligible
Acid Base HCl Cl - H2SO4 HSO 4- HNO3 NO 3- H3O+ H 2O HSO4- SO 42- H3PO4 H2PO4- HF F- HC2H3O2 C2H3O2- H2CO3 HCO 3- H2S HS - H2PO4- HPO 42- NH4+ NH 3 HCO3- CO 32- HPO42- PO 43- H2O OH - OH- O 2- H2 H - CH4 CH 3- 100% protonated in H
2O
Base strength increases Acid strength increases 100% ionized in H
2O
Substances with negligible acidity do not ionize in water. They will not readily give up protons. Their conjugate bases are exceedingly strong.
Strong W e a k Negligible S t r
g W e a k Negligible
Acid Base HCl Cl - H2SO4 HSO 4- HNO3 NO 3- H3O+ H 2O HSO4- SO 42- H3PO4 H2PO4- HF F- HC2H3O2 C2H3O2- H2CO3 HCO 3- H2S HS - H2PO4- HPO 42- NH4+ NH 3 HCO3- CO 32- HPO42- PO 43- H2O OH - OH- O 2- H2 H - CH4 CH 3- 100% protonated in H
2O
Base strength increases Acid strength increases 100% ionized in H
2O
There are seven strong acids: 3 contain a H bound to the very electronegative halogens: HCl hydrochloric acid HBr hydrobromic acid HI hydroiodic acid HF, or hydrofloric acid, is a weak
electronegative, the bond strength between flourine and hydrogen is too strong for HF to easily give up H+.
27 Which of the following is NOT a strong acid?
A HBr B HF C HI D HCl E A and C
answer
There are seven strong acids: 4 are from the very electron drawing
HNO3 nitric acid H2SO4 sulfuric acid HClO3 chloric acid HClO4 perchloric acid Each of these anions has a central atom that is highly electronegative compared to hydrogen. The oxygens that are bonded to that central atom draw more electrons from it making it even more electronegative and likely to take electrons from hydrogen forming H+.
The seven strong acids are: HCl hydrochloric acid HBr hydrobromic acid HI hydroiodic acid HNO3 nitric acid H2SO4 sulfuric acid HClO3 chloric acid HClO4 perchloric acid
The seven strong acids are strong electrolytes because they are 100% ionized. In other words, these compounds exist totally as ions in aqueous solution. For the monoprotic strong acids (acids that donates only one proton per molecule of the acid), the hydronium ion concentration equals the acid concentration. [H3O+] = [acid] So, if you have a solution of 0.5 M HCl, then [H3O+] = 0.5 M
All alkali metals in Group I form hydroxides that are strong bases: LiOH, NaOH, KOH, etc. Only the heavier alkaline earth metals in Group II form strong bases: Ca(OH)2, Sr(OH)
2, and Ba(OH)2.
Again, these substances dissociate completely in aqueous
OH- ions in water.
All strong bases are group of compounds called "metal hydroxides."
28 What would be the [H3O+] in a 0.005 M HBr solution?
answer
In any acid-base reaction, the proton moves toward the stronger base. In
easily releases its proton(s).
HCl(aq) + H2O(l) --> H3O+
(aq) + Cl- (aq)
acid base conj. acid conj. base
H2O is a much stronger
base than Cl-, so the proton moves from HCl to H2O.
W e a k N e g l i g i b l e Strong Weak Negligible
Acid Base HCl Cl - H2SO4 HSO 4- HNO3 NO 3- H3O+ H 2O HSO4- SO 42- H3PO4 H2PO4- HF F- HC2H3O2 C2H3O2- H2CO3 HCO 3- H2S HS - H2PO4- HPO 42- NH4+ NH 3 HCO3- CO 32- HPO42- PO 43- H2O OH - OH- O 2- H2 H - CH4 CH 3- 100% protonated in H
2O
Base strength increases Acid strength increases 100% ionized in H
2O
29 What would be the [OH-] in a 0.034 M NaOH solution?
answer
CH3CO2H(aq) + H2O(l) H3O+(aq) + CH3CO2-(aq)
Acetic acid is a weak acid. This means that only a small percent of the acid will dissociate. The double headed arrow is used only in weak acid or weak base dissociation equations since the reaction can proceed with both the forward and reverse reactions.
A single arrow is used for strong acid or strong bases which dissociate completely since the forward reaction is much more favorable than the reverse reaction.
NaOH Na+ (aq) + OH
30 Strong acids have ___________ conjugate
bases.
weak
neutral
answer
31 HBr, hydrobromic acid is a strong acid. This
means that _______________.
A
aqueous solutions of HBr contain equal concentrations
does not dissociate at all when it is dissolved in water
C
cannot be neutralized by a base D
dissociates completely to H
+ and Br
answer
pH is defined as the negative base-10 logarithm of the concentration of hydronium ion. pH = -log [H3O+] It is a measure of hydrogen ion concentration, [H+] in a solution, where the concentration is measured in moles H+ per liter, or molarity. The pH scale ranges from 0-14. Generally when calculating pH we round to two decimal places.
What is the pH of the solution with hydrogen ion concentration of 5.67x10-8 M (molar)? pH = -log [H+] First, take the log of 5.67x10-8 = -7.25 Now, change the sign from - to + Answer: pH = 7.25
Note: If you take the log of
you will end up with an incorrect answer.
The order of operations:
32 What is the pH of a solution with hydrogen ion
concentration of 1.0 x 10-5 M?
answer
33 What is the pH of a solution with hydrogen
ion concentration of 1.0 x 10-12 M?
2.00
answer
34 What is the pH of a solution whose hydronium
ion concentration is 7.14 x 10-3 M?
answer
35 What is the pH of a solution whose hydronium
ion concentration is 1.92 x 10-9 M?
answer
36 What is the pH of a 0.34 M solution of the strong acid HI? (Remember that strong acids ionize completely)
answer
Application In order for proteins to be digested in the stomach, the pH must be lower than 2.7. If the pH is too high, proteins will not be broken down and may cause a food allergy or indigestion. A patient complains of indigestion and a sample of stomach fluid is taken and the [H3O+] is found to be 3.4 X10-3 M. Is there a problem with the pH?
What is the relationship between [H3O+] and the pH value?
Below are three different [H3O+]. Find the pH of each. pH = -log [H3O+]
Hydrogen ion concentration, [H3O+] in moles/Liter
pH
1.0 x 10-1 1.0 x 10-2 1.0 x 10-10 Clearly, the lower the [H3O+], the _____ the pH.
What is the relationship between [H3 O+], the pH value, and the acidity and basicity of a solution?
low H3O+ High H3O+ high OH- low OH- acidic acidic basic basic neutral
pH
These are the pH values for several common substances.
More acidic More basic
Battery acid lemon juice pure rain or water distilled water sea water baking soda household ammonia household bleach household lye gastric fluid carbonated beverages vinegar
beer coffee egg yolks milk blood milk of magnesia
For more accurate measurements, one uses a pH meter, which measures the voltage in the solution.
For less accurate measurements, one can use Litmus paper “Red” paper turns blue above ~pH = 8 “Blue” paper turns red below ~pH = 5 Or an indicator (usually an organic dye)
2 4 6 8 10 12 14
pH range for color change
Methyl violet Thymol blue Methyl orange Bromothymol blue Phenolphthalein Alizarin yellow R Methyl red
Solution type [H +](M) [OH-] (M) pH value Acidic > 1.0x10-7 <1.0x10-7 <7.00 Neutral =1.0x10-7 =1.0x10-7 =7.00 Basic <1.0x10-7 > 1.0x10-7 >7.00
[H+] > [OH-] There are excess hydrogen ions in solution. [H+] < [OH-] There are excess hydroxide ions in solution. BASE ACID
37 Which of the following solutions would be most
acidic?
A pH = 3 B pH = 2 C pH = 11 D pH = 14 E pH = 1
answer
38 Which of the following (M) solutions would be
LEAST acidic?
A [H3 O+] = 2.3x10-7 B [H3O+] = 9.1x10-3 C [H3O+] = 1.3 x10-2 D [H3O+] = 7.8x10-9 E [H3O+] = 4.5x10-4
answer
39 Which of the following solutions would have the
highest pH?
A [OH-] =3.4x10-3 B [H3O+] = 5.4x10-11 C [OH-] = 3.4x10-12 D [H3O+] =5.4x10-2 E [OH-] =3.4x10-1
answer
40 Which solution below has the highest
concentration of hydroxide ions? A pH = 3.21 B pH = 7.00 C pH = 8.93 D pH = 12.60
answer
41 Which solution below has the lowest
concentration of hydrogen ions? A pH = 11.40 B pH = 8.53 C pH = 5.91 D pH =1.98
answer
42 For a basic solution, the hydrogen ion
concentration is ______________ than the hydroxide ion concentration.
A greater than B less than C equal to D Not enough information.
answer
43 For an acidic solution, the hydroxide ion
concentration is ______________ than the hydrogen ion concentration.
A greater than B less than C equal to D Not enough information.
answer
44 Which of the following would turn blue litmus paper
red? A Solution with [OH-] = 2.3 E-7 M B Solution with pH = 4
C Solution with pOH = 2 D A and C E B and C
answer
Because of the base-10 logarithm, each 1.0-point value on the pH scale differs by a value of ten.
A solution with pH = 9 has a hydrogen ion concentration, [H+], that is 10 times more than a pH = 10 solution. A solution with pH = 8 has a hydrogen ion concentration, [H+], that is 102 or 100 times more than a pH = 10 solution.
45 A solution with pH = 3 has a hydrogen ion
concentration that is __________than a solution with pH = 5. A 2x more B 2x less C 100x more D 100x less
answer
46 A solution with pH = 14 has a hydrogen ion
concentration that is __________than a solution with pH = 11. A 3x more B 3x less C 1000x more D 1000x less
answer
Just as the pH of a solution can be calculated by: pH = -log[H3O+] The pOH of a solution can be calculated by: pOH = - log[OH-] Recall that the [OH-] and [H3O+] are inversly related so pH and pOH are as well. 0 7 14 low pH 14 7 0 high pOH low pOH high pH
What is the pOH of a solution that has a [OH-] = 2.3 E-5 M? pOH = - log[OH-] pOH = - log(2.3 E-5) = 4.63
47 What is the pOH of a solution with a
[OH-] = 2.7 x10-2 M?
A 2.7 B 12.43 C 1.57 D -1.57 E -2.7
answer
Once we have calculated pOH, it is very easy to calculate pH. Remember that our solvent for all of our reactions is Water. We also know that we have a Kw value for water of 1 x 10-14. This is ALWAYS true for water. We can also determine the following equations:
Throwing in our logarithms for pH, pOH and pKw we end up with this:
Remember that Kw is a constant and if we that the negative log of that constant we get 14 so.....
Therefore, if we have a pOH and we want to convert it to pH, so long as we are using water for our solvent, we can use the below equation to determine the pH of the solution.
In other words, to find the pH of a basic compound, you first must need to determine the pOH of that compound and then use that to determine the pH. Remember that pOH is calculated using [OH-] and pH is calculated using [H+]. Other then that, there is no difference in the steps used to calculate pOH and pH.
48 What is the pOH of a solution with a pH =5?
A 5 B 15 C 7 D 8 E 9
answer
49 What is the pH of an aqueous ammonia solution with
a [OH-] = 1 x 10-4 M?
A 4 B 1 x10-4 C 10 D 1 x10-10 E 3
answer
50 What is the pOH of an aqueous HCl solution with a
[H3O+] = 2.7 x10-1 M?
A 13.43 B 0.57 C 2.7 x10-1 D 2.7 x10+1 E 12.43
answer
51 What would be the pH of a 0.045 M NaOH solution? (Recall that NaOH is a strong base and will ionize completely)
answer
52 Which of the following would be LEAST acidic?
A pOH = 2 B pOH = 4 C pH = 10 D pH = 2 E pH = 11
answer
If given a pH, one can determine the [H3O+] by: 10-pH = [H3O+] If given a pOH, one can determine the [OH-] by: 10-pOH = [OH-]
What is the [H3O+] in a lemon juice solution with a pH = 3.5? 10-3.5 = 3.2x10-4 M What is the [H3O+] in a bottle of soda with a pOH = 11.4? 14 = pOH + pH 14 = 11.4 + pH pH = 2.6 10-2.6 = 2.5x10-3 M
53 What is the OH- ion concentration if the pH of a
solution is 6?
A
1 x10-6
B
1 x10-8
C
1 x106
D
1 x1012
answer
54 What is the OH- concentration if the pH of a solution
is 11?
A
1 x 10-4
B
1 x10-3
C
1 x 10-11
D
1 x1011
answer
55 What is the hydrogen ion concentration (M) in a solution of Milk of Magnesia whose pH = 9.8?
A 9.8 M B 9.8x10-10 M C 4.2 M D 1.6x10-10 M E 4.2x10-10 M
answer
56 What is the hydronium ion concentration in a
solution whose pH = 4.29?
answer
57 For a 1.0-M solution of a strong acid, a
reasonable pH would be_____. A B 6 C 7 D 9 E 13
answer
58 For a 1.0-M solution of a weak base, a reasonable
pH would be_____. A 2 B 6 C 7 D 9 E 14
answer
A buffer is a solution that can maintain a nearly constant pH when diluted or when strong acids or strong bases are added to it. A buffer solution is made up of a weak acid, HA, and its conjugate base, A-, or a weak base and its conjugate acid.
http://chemcollective.org/activities/tutorials/buffers/buffers3
When a strong base is added to a buffer the hydroxide OH- from the strong base reacts with the weak acid, which gives up its H+ to form
http://chemcollective.org/activities/tutorials/buffers/buffers3
If a strong acid is added to a buffer it will react with the weak conjugate base to form a weak acid that does not readily dissociate, and, therefore, does not significantly alter the pH.
http://chemcollective.org/activities/tutorials/buffers/buffers3
59 Buffers are composed of
A
Strong acids to neutralize strong bases
B
Strong bases to neutralize strong acids
C
A weak acid and its conjugate base
D
A strong acid and its conjugate base
60 A buffer solution contains carbonic acid (H2CO3) and bicarbonate (HCO3-). When a small amount
A The HCl dissociates and the H
+ significantly lowers the
pH of the solution. B The HCl dissociates and the H+ reacts with the bicarbonate to form a neutral compound. C The pH of the solution remains stable. D Both b and c
61 A buffer solution contains formic acid (HCO2H) and sodium formate (HCO2Na). When a small amount of NaOH is added to the buffer
A The NaOH dissociates and the OH
the pH of the solution. B The formic acid neutralizes the hydroxide to form water. C The sodium formate neutralizes the hydroxide. D None of the above
The body maintains the pH of blood at around 7.4. If the pH level changes just a few tenths of a pH unit, serious health consequences can result. A decrease in blood pH is called acidosis, an increase is called alkalosis. There are 3 systems that regulate the pH of blood. The bicarbonate system is the most important and is controlled by the rate of respiration. In the bicarbonate system, carbon dioxide combines with water to form carbonic acid, which dissociates to form bicarbonate and hydrogen ions. CO2 + H2O H2CO3 HCO3- + H+
62 Based on the figure below, holding one's breath can lead to which condition?
A Alkalosis B Acidosis C Hemolysis
63 How does the body's response to the condition in the previous question help restore the pH of the blood?
A Breathing out reduces the amount of CO
2 present,
thereby reducing the production of carbonic acid. B Breathing in increases the amount of oxygen in the blood. C Breathing has no effect on the pH of blood.