Chemistry Acids and Bases

Question 1

A particularly common indicator is ___, which turns red in acidic solutions an blue in basic solutions

Answer 1

litmus paper

Question 2

___ react with bases to form water and a salt
Non oxidizing acids react with metals to produce hydrogen gas
Aqueous base and acidic solutions can conduct electricity

Answer 2

acids

Question 3

Arrhenius defined an acid as a species that produces H+ (a proton) in an ___ and a base as a species that produces OH- (a hydroxide ion) in an aqueous solution

Answer 3

aqueous solution

Question 4

___ definitions of acids and bases fail to describe acidic and basic behavior in nonaqueous media

Answer 4

Arrhenius

Question 5

A ___ is a species that donates protons, while a Bronsted-Lowry base is a species that accepts protons
NH3 can accept a proton but is not an Arrhenius base since it is not in aqueous solution

Answer 5

Bronsted-Lowry acid

Question 6

Bronsted-Lowry acids and bases always occur in pairs, called ___. A conjugate acid is defined as the acid formed when a base gains a proton. Similarly, a conjugate base is formed when an acid losses a proton

Answer 6

conjugate acid-base pairs

Question 7

H3O+ is the ___ of the base H2O and NO2- is the conjugate base of HNO2
H3O+ -> H2O + H+
HNO2 -> NO2- + H+

Answer 7

conjugate acid

Question 8

Lewis defined an acid as an electron-pair acceptor and a ___ as an electron-pair donor. Every Arrhenius acid is a Bronsted-Lowry acid, every Bronsted-Lowry acid is also a Lewis acid (and likewise for bases)

Answer 8

base

Question 9

The Lewis definition encompasses some ___ not included within the Bronsted-Lowry definition.
BCl3 and AlCl3 can each accept an electron pair and are therefore Lewis acids despite their inability to donate protons

Answer 9

species

Question 10

Lewis ___ (and occasionally acids) are sometimes referred to as ligands

Answer 10

bases

Question 11

Acids formed from \_\_\_ whose names end in -ide have the prefix hydro- and the ending -ic
F- Fluoride
HF Hydrofluoric acid
Br- Bromide
HBr Hydrobromic acid

Answer 11

anions

Question 12

Acids formed from ___ are called oxyacids. If the anion ends in -ite (less oxygen), then the acid will end with -ous acid. If the anion ends in -ate (more oxygen), then the acid will end with -ic acid

Answer 12

oxyanions

Question 13

ClO- \_\_\_
HClO Hypchlorous acid
ClO2- Chlorite 
HClO2 Chlorous acid
ClO3- Chlorate
HClO3 Chloric acid
ClO4- Perchlorate
HClO4 Perchloric acid
NO2- Nitrite
HNO2 Nitrous acid
NO3- Nitrate 
HN3 Nitric acid

Answer 13

Hypochlorite

Question 14

pH = -log[H+]
pOH = -log[OH-]
In any aqueous solution , the H2O solvent ___ slightly in a process called autoionization
H2O (l) ->

Answer 14

dissociates

Question 15

As [H+] goes up, the pH goes down (more ___); and as K sub a increases 9strong acid), pK sub a goes down

Answer 15

acidic

Question 16

A method of estimating p-scale values:
If the ___ is written in proper scientific notation, it will look like n x 10 ^ -m, where n is a number between 1 an d10. The log of this product can be written as log(nx10^-m) = -m + log n, and the negative log is thus m - log n. Now, since n is a number between 1 and 10, its logarithm is a fraction between 0 an d1; thus, m - log n is between m-1 and m. Furthermore, the larger the n, the larger the log n, and therefore the closer the answer is to m -1

Answer 16

nonlogarithmic value

Question 17

The strength of an acid or base is determined by its ability to ___ in aqueous solution. The more an acid or base dissociates in the presence of water molecules, the stronger it is

Answer 17

ionize

Question 18

The ___ is inherently tied to the strength of its conjugate base. Most acids are neutral molecules that upon deprotonation leave a conjugate base that is an anion. Those conjugate bases that cannot stabilize the negative charge well quickly capture a proton to reform the acid molecule; thus, there are less dissociated acid molecules in solution and it is a weaker acid. Acids that have a conjugate base capable of stabilizing the negative charge, such as through resonance or induction, will have a greater degree of ionization

Answer 18

strength of an acid

Question 19

For incredibly ___ and bases (near complete dissociation), the conjugate is so weak that it is practically inert

Answer 19

strong acids

Question 20

Hence, in a 1 M ___ of NaOH, complete dissociation gives one mole of OH- ions per liter of solution
pH = 14 - (-log[OH-])=14 + log[1]

Answer 20

solution

Question 21

Note that the [OH-] contributed by the ___ of H2O is considered to be negligible

Answer 21

autoionization

Question 22

Given the pH of a 1 x 10^-8 M HCl solution
K sub w = [H+][OH-]
1 x 10^-14 = [x + 1 x 10^-8][x]
note that H+ from water and HCl are added together due to the ____
Solving for x gives x = 9.5 x 10^-8 so [H+ sub total] = [H+ from HCl + H+ from water] = 1.05 x 10^-7 M
and pH = -log(1.05 x 10^-7) = 6.98
The pH is slightly less than 7, as should be expected for a very dilute yet acidic solution

Answer 22

common ion effect

Question 23

Strong Acids
HClO4 (perchloric acid)
HNO3 (nitric acid)
H2SO4 (sulfuric acid)
HCl (hydrochloric acid)

Strong Bases
NaOH (sodium hydroxide)
KOH (potassium hydroxide)
Ca(OH)2 (calcium hydroxide)
other soluble \_\_\_ of Group IA and IIA metals

Answer 23

hydroxides

Question 24

For a ___:

HA (aq) + H2O (l) ->

Answer 24

weak acid

Question 25

The ___, K sub a, is a specific type of K sub eq that measures the degree to which an acid dissociates by showing the ratio of concentrations of the products) the conjugate base and the H+ donated) to that o f the reactant (the original acid) K sub a = [H3O+][A-]/[HA] The weaker the acid , the smaller the K sub a. The strong vs weak acid designation is based on this value; strong acids have a K sub a > 1 while weak acids have K sub a < 1

Answer 25

acid dissociation constant

Question 26

The ___ , K sub b, is a measure of the degree to which a base dissociates

Answer 26

base dissociation constant

Question 27

The weaker the ___, the smaller its K sub b. Strong bases have a K sub b > 1 while weak bases have a K sub b < 1 K sub b = [B+][OH-]/[BOH]

Answer 27

base

Question 28

To find the K sub a of the conugate acid HCO3-, the reaction with water must be considered: HCO3 - (aq) + H2O (l) ->

Answer 28

dissociation constant

Question 29

Calculate the ___ of H+ in a 2.0 M aqueous solution of acetic acid, CH3COOH (K sub a = 1.8 x 10^-5) First write the equilibrium reaction: CH3COOH (aq) -> H+(aq) + CH3COO- (aq) K sub a = [H+][CH3COOO-]/[CH3COOH] = 1.8 x 10^-5 Because acetic acid is a weak acid, the concentration of CH3COOH at equilibrium is equal to tis initial concentration, 2.0M, less the amount dissociated, x. Likewise, [H+] = [CH3COO-] = x, since each molecule of CH3COOH dissociates into one [H+} ion and one CH3COO- ion. Thus, the equation can be rewritten as follows: K sub a = [x][x]/[2.0-x] = 1.8 x 10^-5 We can approximate that 2.0-x is approximately 2.0 since acetic acid is a weak acid that only slightly dissociates in water, and x will be small. Multiplying or dividing by small numbers can have large effects, but adding or subtracting small numbers is not statistically significant. The math can be made much simpler by ignoring x values that are added or subtracted from (comparably) large numbers: K sub a = [x][x]/2.0 1.8 x 10^-5 = x^2/2 3.6x10^-5 = x^2 x = 6x10^-3 M A rule of thumb is that the approximation is valid as long as x is less than 5 percent of the initial concentration

Answer 29

concentration

Question 30

Acids and ___ may react with one another, forming a salt and (often, but not always) water in what is termed a neutralization reaction

Answer 30

bases

Question 31

The ___ may precipitate out (of a neutralization reaction) or remain ionized in solution depending on its solubility and the amount produced

Answer 31

salt

Question 32

The reverse ___, in which the salt ions react with water to give back the acid or base, is known as hydrolysis

Answer 32

reaction

Question 33

Four combinations of strong and weak ___ and bases are possible: 1 strong acid + strong base: e.g., HCl + NaOH -> NaCl + H2O 2 strong acid + weak base: e.g., HCl + NH3 -> NH4Cl 3 weak acid + strong base: e.g., HClO + NaOH -> NaClO + H2O 4 weak acid + weak base: e.g., HClO + NH3 ->

Answer 33

acids

Question 34

Weak acids have weak conjugate bases and vice versa. ___ have conjugate bases so weak that they are inert

Answer 34

strong acids

Question 35

The products of a ___ between equal concentrations of a strong acid and a strong base are a salt and water

Answer 35

reaction

Question 36

The ___ of a reaction between a strong acid and a weak base is also a salt, but usually no water is formed since weak bases are usually not hydroxides

Answer 36

product

Question 37

Another way to consider this reaction is that the weak acid cation will react with the water ___, reforming the weak base HCl (aq) + NH3 (aq) -> 7); the weak base anion (ClO- in our example will react with H2O solvent which leaves OH- to raise the pH The pH of a solution containing a weak acid and a weak base depends on the relative strengths of the reactants. The acid HClO has a K sub a = 3.2 x 10^-8, and the base NH3 has a K sub b =1.8 x 10^-5. Thus, an aqueous solution of HClO and NH3 is basic, since the K sub a for HCLO is smaller than the K sub b for NH3, and therefore NH3 is the stronger reactant

Answer 37

solvent

Question 38

The relative ___ or basicity of an aqueous solution is determined by the relative concentrations of acid and base equivalents

Answer 38

acidity

Question 39

An ___ is equal to one mole of H+ (H3O+) ions; a base equivalent is equal to one mole of OH- ions

Answer 39

acid equivalent

Question 40

Some acids are ___, that is, each mole of the acid or base liberates more than one acid or base equivalent

Answer 40

polyvalent

Question 41

H2SO4 (aq) -> H+ (aq) + HSO4- (aq) | HSO4- (aq) ->

Answer 41

acid equivalents

Question 42

The quantity of ___ is directly indicated by the solution's normality (N) where N = Molarity x equivalents/mol. Because each mole of H3PO4 can liberate 3 moles (equivalents) of H+, a 2M H3PO4 solution would be 6N (6 normal)

Answer 42

acidic or basic capacity

Question 43

Another useful measurement is ___. The equivalent weight is calculated by taking the molecular weight and dividing by the number of equivalents per mole. The gram molecular weight of H2SO4 is 98 g/mol. Because each mole liberates two acid equivalents, the gram equivalent weight of H2SO4 would be 98/2 = 49 g; that is the dissociation of 49 g of H2SO4 would release one acid equivalent. Common polyvalent acids include H2SO4, H3PO4, and H2CO3

Answer 43

equivalent weight

Question 44

An amphoteric, or amphiprotic, species is one that can act either as an ___, depending on its chemical environment

Answer 44

acid or a base

Question 45

In the Bronsted-Lowry sense, an amphoteric species can either gain or lose a proton. When water reacts with a base, it behaves as an acid: H2O +B ->

Answer 45

conjugate base

Question 46

___ is a procedure used to determine the molarity of an acid or base

Answer 46

titration

Question 47

Titration is accomplished by reacting a known ___ or a solution of unknown concentration with a known volume or a solution of known concentration. When the number of acid equivalents equals the number of base equivalents added, or vice versa, the equivalence point is reached

Answer 47

volume

Question 48

While a strong acid/strong base titration will have an ___ at pH 7, the equivalence point need not always occur at pH 7. Also, when titrating polyprotic acids or bases, there are several equivalence points, as each acidic or basic species is titrated separately

Answer 48

equivalence point

Question 49

The equivalence point in a ___ is estimated in two common ways: either by plotting pH (measured with a pH meter) of the solution as a function of added titrant on a graph of by watching for a color change of an added indicator

Answer 49

titration

Question 50

Indicators are ___ or bases that have different colors in their undissociated and dissociated states. indicators are used in low concentrations and therefore do not significantly alter the equivalence point. The point at which the indicator actually changes color is not the equivalence point but is called the end point; this point is not significant mathematically but rather is a practical way to ensure the reaction has gone to completion. If the titration is performed well, the volume difference (and therefore the error) between the end point and the equivalence point is small and may be corrected for or ignored

Answer 50

weak organic acids

Question 51

A ___ consists of a mixture of a weak acid and its salt (which consists or its conjugate base and a cation) or a mixture of a weak base and its salt (which consists of its conjugate acid an an ion

Answer 51

buffer solution

Question 52

Consider a ___ solution of acetic acid and sodium acetate: CH3COOH -> H+ + CH3COO- CH3COONa -> Na+ + CH3COO-

Answer 52

buffer

Question 53

The Henderson-Hasselbalch equation is used to estimate the pH of a ___ in the buffer region where the concentrations of the species and its conjugate are present in approximately equal concentrations. For a weak acid buffer solution: pH = pK sub a + log[conjugate base]/[weak acid] Note that when [conjugate base] = [weak acid] (in titration, halfway to the equivalent point), the pH = pK sub a because log 1 = 0. Likewise, for a weak base buffer solution: pOH = pK sub b + log[conjugate acid]/[weak base] pOH = pK sub b when [conjugate acid] = [weak base]

Answer 53

solution

Question 54

When a small amount of NaOH is added to the buffer, the OH- ions from the NaOH react with the acetic acid in the buffer solution such that: CH3COOH + NaOH ->

Answer 54

buffer

Question 55

Instead of the addition of a strong ___ (HCl), there is now a weak aci present (CH3COOH). Just as with the strong base, the pH shift will be quite small

Answer 55

acid