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gen chem 2 > chap 14-16 > Flashcards

chap 14-16 Flashcards

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1
Q

What is a buffer?

A

Solutions that resist large changes in pH when small amounts of acid (H3O+) or base (OH-) are added.

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2
Q

What are the components of a buffer?

A

Made up of two components: an acid and a base component.

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3
Q

How can a buffer be made from a weak acid?

A

A buffer can be made from a weak acid and its conjugate base.

Example: HF and F-

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4
Q

How can a buffer be made from a weak base?

A

A buffer can be made from a weak base and its conjugate acid.

Example: NH3 and NH4

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5
Q

What is an example of a buffer system in nature?

A

H2CO3 and HCO3- resist large changes in pH.

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6
Q

What happens to pH when a small amount of acid or base is added to an unbuffered solution?

A

The pH of the unbuffered solution significantly changes.

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7
Q

What happens to pH when a small amount of acid or base is added to a buffered solution?

A

The pH of the buffered solution does not significantly change.

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8
Q

What happens to the pH of a buffer with a weak acid and its conjugate base when a base is added?

A

The added base is neutralized by the acid component in the buffer, and the pH of the buffer slightly increases.

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9
Q

What happens to the pH of a buffer with a weak acid and its conjugate base when an acid is added?

A

The added acid is neutralized by the base component in the buffer, and the pH of the buffer slightly decreases.

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10
Q

What happens to the pH of a buffer with a weak base and its conjugate acid when a base is added?

A

The added base is neutralized by the acid component in the buffer, and the pH of the buffer slightly increases.

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11
Q

What happens to the pH of a buffer with a weak base and its conjugate acid when an acid is added?

A

The added acid is neutralized by the base component in the buffer, and the pH of the buffer slightly decreases.

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12
Q

What defines the effectiveness of a buffer?

A

An effective buffer neutralizes small to moderate amounts of added acid or base without a large change in its pH.

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13
Q

When is a buffer most effective?

A

A buffer is most effective when the concentrations of acid and conjugate base are equal.

Then, buffer has equal capacity towards a strong acid and a strong base.

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14
Q

What is the buffer range?

A

The pH range at which the buffer can be effective is when 0.1 < [base]/[acid] < 10.

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15
Q

What is the effective pH range of a buffer?

A

The effective pH range of a buffer is pKa ± 1.

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16
Q

What should you consider when choosing an acid to make a buffer?

A

Choose one whose pKa is closest to the pH of the buffer.

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17
Q

What is the Henderson–Hasselbalch equation?

A

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

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18
Q

What makes a conjugate acid-base pair?

A

They differ by one H⁺ (e.g., HA and A⁻)

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19
Q

When is a cation pH-active?

A

If it comes from a weak base

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20
Q

When is an anion pH-active?

A

If it comes from a weak acid

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21
Q

What is the equivalence point in a titration?

A

The point where moles of acid = moles of base

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22
Q

What is the analyte in a titration?

A

The solution of unknown concentration in the flask

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23
Q

What is the titrant?

A

The solution of known concentration in the burette

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24
Q

What tools monitor titration progress?

A

pH meter or indicator

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25
What is the pH at equivalence for strong acid + strong base?
pH = 7
26
What happens when an ionic compound dissolves in water?
It dissociates into hydrated ions and establishes an equilibrium with the solid phase.
27
What is Ksp?
The equilibrium constant for the dissociation of an ionic compound into its aqueous ions. Temperature can change the value.
28
What is the difference between Q and Ksp?
Ksp uses ion concentrations at equilibrium; Q uses ion concentrations under any conditions.
29
What is the Ksp expression for CaF₂?
Ksp = [Ca²⁺][F⁻]²
30
What is the common ion effect?
The solubility of an ionic compound is lower in a solution containing a common ion than that in pure water.
31
What happens to the solubility of CuS if Na₂S is added?
It decreases due to the common S²⁻ ion (common ion effect).
32
What does it mean when Q < Ksp?
The solution is unsaturated; more solid can dissolve; no precipitate forms.
33
What does it mean when Q = Ksp?
The solution is saturated; no additional solid dissolves; equilibrium is reached.
34
What does it mean when Q > Ksp?
The solution is supersaturated; excess solid will precipitate out.
35
How does pH affect solubility for compounds with basic anions?
Lower pH (acidic) increases solubility; higher pH (basic) decreases solubility.
36
What is selective precipitation?
Separation of ions based on differences in their solubility with a specific reagent. The ion that requires the smallest amount of added ion precipitates first.
37
Q: How does the Lewis theory define acids and bases?
Acid: Electron pair acceptor; Base: Electron pair donor.
38
Q: Name examples of Lewis acids.
BF₃, AlCl₃, H⁺, CO₂, Fe³⁺
39
Q: Name examples of Lewis bases.
A: NH₃, OH⁻, F⁻, CN⁻
40
Q: What defines a spontaneous process?
A: Occurs without outside assistance and does not require continuous energy input.
41
What defines a non-spontaneous process?
Occurs only with outside assistance. Continuous input of energy is required.
42
What is entropy (S)?
A measure of disorder or freedom of motion in a system. Units: J/K
43
What is the Boltzmann equation for entropy?
S = k ln(W), where k is Boltzmann's constant and W is the number of microstates.
44
What happens to entropy as the number of microstates increases?
Entropy increases.
45
What are microstates?
The energetically equivalent ways to arrange the components. Possible positions of equal energy. 16 microstates possible. As microstates increase, s increases.
46
∆S is postive (∆S> 0) as
entropy increases, number of moles increase, temperature increases, molecular complexity, dissolving a solid
47
An decrease in entropy, ∆S is ___?
entropy decreases, number of moles decreases, temperature decreases, molecular complexity decreases, dissolving a gas
48
What is the Second Law of Thermodynamics?
Entropy of the universe increases for a spontaneous process
49
What is the criteria for Spontaneity?
∆G< 0 and ∆S-universe> 0. (for non spont. its opp)
50
∆H=- ∆S=+ at either low or high temp. Spontaneity?
Always spontaneous (∆G < 0)
51
∆H=+ ∆S=- at either low or high temp. Spontaneity?
Always Non-spontaneous (∆G > 0)
52
∆H=- ∆S=- at low temp
spontaneous (∆G < 0)
53
∆H=- ∆S=- at high temp
Non-spontaneous (∆G > 0)
54
∆H=+ ∆S=+ at low temp
Non-spontaneous (∆G > 0)
55
∆H=+ ∆S=+ at high temp
spontaneous (∆G < 0)
56
What is the standard condition value of K for spontaneity when ∆𝐺𝑟𝑥𝑛0 = 0?
K = 1
57
What is the standard condition value of K for spontaneity when ∆𝐺𝑟𝑥𝑛0 > 0?
K < 1
58
What is the standard condition value of K for spontaneity when ∆𝐺𝑟𝑥𝑛0 < 0?
K > 1
59
What is the nonstandard condition value of Q for spontaneity when ∆𝐺𝑟𝑥𝑛 = 0?
Q = K
60
What is the nonstandard condition value of Q for spontaneity when ∆𝐺𝑟𝑥𝑛 > 0?
Q > K
61
What is the nonstandard condition value of Q for spontaneity when ∆𝐺𝑟𝑥𝑛 < 0?
Q < K
62
What is the spontaneity condition at equilibrium?
At equilibrium
63
What is the spontaneity condition when ∆𝐺𝑟𝑥𝑛 > 0?
nonspontaneous
64
What is the spontaneity condition when ∆𝐺𝑟𝑥𝑛 < 0?
spontaneous

gen chem 2 (2 decks)

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