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CHEM 203 > Acids & Bases > Flashcards

Acids & Bases Flashcards

1
Q

What is a Bronsted Lowery Acid?

A

An acid donates the proton or hydrogen ion.

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2
Q

What is a Bronsted Lowery Base?

A

A base accepts the proton or hydrogen ion.

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3
Q

What is an amphiprotic species?

A

Depending on the circumstances they can accept protons or they can donate protons.

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4
Q

What is the difference between a weak acid or base and a strong acid or base?

A

A strong acid or base nearly dissociates 100% of the acid or base whereas a weak acid or base dissociates a very low amount of the acid or base.

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5
Q

What is Ka?

A

The equilibrium constant for the reaction of a Bronsted Lowery Acid that produces H3O+ this is the acid dissociation constant.

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6
Q

What is Kb?

A

The equilibrium constant for the reaction of a Bronsted Lowery Base that produces OH- this is the base dissociation constant.

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7
Q

What is Kw?

A

This is the ionization of water as some water molecules ionize into H3O+ and OH- because of the slight conductivity.

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8
Q

What is the small x approximation?

A

When the initial concentration is much greater than the ka or kb we can assume that the x will not have an effect on the initial concentration. However we must check it by taking the x/initial concentration and it must be less than 5%.

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9
Q

What are soluble salts?

A

These are substances that dissociate 100% in water thus if the ions react with water and form a strong acid or base they will dissociate once more so they do not form a strong acid or base only a weak acid or base.

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10
Q

How is the strength of the acid/base related to its conjugate?

A

The stronger an acid/base the weaker its conjugate acid/base.

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11
Q

What is the large X assumption?

A

If the change in X is small enough to the point where it does not change the initial concentration.

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12
Q

How can you tell if you should use the small X assumption?

A

Ka &laquo_space;Initial concentration

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13
Q

What happens when the Ka values are different?

A

If the Ka values are different observe the higher Ka value that acid is stronger and will dissociate close to 100%.

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14
Q

What is a strong base?

A
  1. ) Reacts completely with water and forms HA and OH- ions these are OH’s bound to group 1 or 2 ions.
  2. ) Have very large Kb values.
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15
Q

What is a strong acid?

A
  1. ) Reacts completely with water and forms A- and H3O+.

2. ) Have very large Ka values.

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16
Q

What does no Ka mean?

A

This means that the Ka value is so large that it has reached completion.

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17
Q

What happens to a very weak acid in water?

A

A very weak acid does not produce H3O+ in water.

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18
Q

What is a weak acid?

A
  1. ) Does not react completely with water and forms A- and H3O+.
  2. ) Have moderate Ka values.
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19
Q

What is a weak base?

A
  1. ) Does not react completely with water and forms HA and OH-.
  2. ) Have moderate Kb values.
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20
Q

What happens when the concentrations are different?

A

If there is a large amount of the reactant concentration then there will be a higher concentration of H3O+.

21
Q

What is a % dissociation?

A

The percentage of the acid or base that dissociates in solution and the percentage is dependent on the strength of the acid or base.

22
Q

How is pKa/Kb related to Ka or Kb?

A

The smaller the pka/pkb value the larger the ka or kb value which means that the stronger the acid or base respectively.

23
Q

What is a titrant?

A

This is the known solution in the burette where the identity, volume and concentration are known.

24
Q

What is a titrand?

A

This is the unknown solution in the beaker where the identity is unknown, volume is known and concentration is unknown. Along with the acid base indicator to tell when the reaction has reached its end. Also water where the concentration does not change but the number of moles do change.

25
Q

What is the half equivalence point?

A

This is when the number of moles of the weak acid is equal to the number of moles of the conjugate base.

26
Q

What is the equivalence point?

A

This is when the weak acid has been consumed by the strong base and no more conjugate base can form.

27
Q

What occurs before the equivalence point?

A

There is excess H3O+ in the solution and the pH can be determined as a result.

28
Q

What occurs at the equivalence point?

A

The acid is exactly neutralized and the pH > 7 because the substance is basic.

29
Q

What occurs after the equivalence point?

A

There is excess OH- in the solution and the pH > 7 because the substance is basic.

30
Q

What is the objective at the equivalence point?

A

To determine the volume of the strong base that is able to consume all of the weak acid and not form anymore conjugate base.

31
Q

Why do na = nOH- = nHAi?

A

The number of moles of the conjugate base is equal to the number of moles of hydroxide and the acid at the equivalence point because at this point the acid is consumed by the hydroxide entirely and there are no more moles of OH- or HA only A- therefore the A- = OH- = HA.

32
Q

What is the endpoint?

A

This is the point that can be determined experimentally, visually, and is value dependent on the technique.

33
Q

What is the difference between the equivalence and endpoint?

A

At the equivalence point there is no more of the limiting reagent, there is an exact amount of titrant that is added, and it is a theoretical point. Whereas the endpoint is This is the point that can be determined experimentally, visually, and is value dependent on the technique.

34
Q

What is a potentiometric titration curve?

A

Potentiometric titration is a technique similar to direct titration of a redox reaction. It is a useful means of characterizing an acid. No indicator is used; instead the potential is measured across the titrand, typically an electrolyte solution.

35
Q

What are the 4 factors that affect the shape of the titration curve?

A
  1. ) Acid => HA concentration
  2. ) Identity
  3. ) Base => OH- concentration
  4. ) Acid => Volume of the acid
36
Q

What is initial pH affected by?

A
  1. ) The initial concentration of the HA

2. ) The HA strength

37
Q

What does the equivalence point volume depend on?

A
  1. ) Number of moles of HA

2. ) Concentration of strong base used

38
Q

What does the equivalent point pH depend on?

A
  1. ) Slightly basic for a weak acid

2. )The stronger the HA the weaker the conjugate base

39
Q

What does the pH at the half equivalence point depend on?

A

1.) Strength of HA

40
Q

What if the acid-base indicator ratio is&raquo_space; 1?

A

The colour will be the second colour of the indicator.

41
Q

What if the acid-base indicator ratio is &laquo_space;1?

A

The colour will be the first colour of the indicator.

42
Q

What if the acid-base indicator ratio is = 1?

A

The colour will be a mix of the 2 colours present and this means that the pH ~ pKa.

43
Q

What is a buffer?

A

These are solutions that are able to withstand the addition of a strong acid or base and it must contain similar amounts of both the weak acid and weak base in a conjugate acid/base pair.

44
Q

What is the pH range?

A

This is the pH range over which a solution is a buffer.

45
Q

What is the buffer ratio?

A

This is the ratio of conjugate base to weak acid.

46
Q

What are the assumptions that we make?

A
  1. ) The concentration of A- at equilibrium and initially is the same.
  2. ) The concentration of HA at equilibrium and initially is the same.
  3. ) The HA and A- have the same volume therefore the buffer ratio can be of moles or concentrations.
47
Q

What are the 2 steps that are required to prepare a buffer solution with a target pH?

A
  1. ) Choose the acid that is based on the pka value where the pH is about the same as the pka.
  2. ) The buffer ratio is used to adjust the A- and the HA to obtain the correct pH.
48
Q

When does a buffer not work?

A

The amount of strong acid or base is higher in amount than the weak conjugate acid/base.

CHEM 203 (7 decks)

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