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DAT > Chemistry Acids and Bases > Flashcards

Chemistry Acids and Bases Flashcards

1
Q

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

A

litmus paper

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2
Q

___ 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

A

acids

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3
Q

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

A

aqueous solution

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4
Q

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

A

Arrhenius

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5
Q

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

A

Bronsted-Lowry acid

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6
Q

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

A

conjugate acid-base pairs

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7
Q

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

A

conjugate acid

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8
Q

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)

A

base

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9
Q

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

A

species

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10
Q

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

A

bases

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11
Q 
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
A

anions

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12
Q

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

A

oxyanions

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13
Q 
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
A

Hypochlorite

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14
Q

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

A

dissociates

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15
Q

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

A

acidic

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16
Q

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

A

nonlogarithmic value

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17
Q

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

A

ionize

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18
Q

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

A

strength of an acid

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19
Q

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

A

strong acids

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20
Q

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]

A

solution

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21
Q

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

A

autoionization

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22
Q

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

A

common ion effect

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23
Q 
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
A

hydroxides

24
Q

For a ___:

HA (aq) + H2O (l) ->

A

weak acid

25
Q

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

A

acid dissociation constant

26
Q

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

A

base dissociation constant

27
Q

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]

A

base

28
Q

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

A

dissociation constant

29
Q

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

A

concentration

30
Q

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

A

bases

31
Q

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

A

salt

32
Q

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

A

reaction

33
Q

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 ->

A

acids

34
Q

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

A

strong acids

35
Q

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

A

reaction

36
Q

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

A

product

37
Q

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

A

solvent

38
Q

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

A

acidity

39
Q

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

A

acid equivalent

40
Q

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

A

polyvalent

41
Q

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

HSO4- (aq) ->

A

acid equivalents

42
Q

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)

A

acidic or basic capacity

43
Q

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

A

equivalent weight

44
Q

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

A

acid or a base

45
Q

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 ->

A

conjugate base

46
Q

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

A

titration

47
Q

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

A

volume

48
Q

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

A

equivalence point

49
Q

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

A

titration

50
Q

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

A

weak organic acids

51
Q

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

A

buffer solution

52
Q

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

A

buffer

53
Q

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]

A

solution

54
Q

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 ->

A

buffer

55
Q

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

A

acid

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