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Chemistry 30 AP > Chapter 16: Equilibrium in Acid-Base Systems: > Flashcards

Chapter 16: Equilibrium in Acid-Base Systems: Flashcards

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1
Q

What is an ideal buffer?

A

One in which the concentration of an acid and its conjugate base are the same.

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2
Q

What happens when one of the 5 strong acids (since H2SO4 excluded) react with a strong base?

A

A quantitative reaction with an endpoint at ph=7

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3
Q

What entities cannot be part of a buffer region?

A

H30+ and OH- (which is why many SA/SB rxns have only one buffer region)

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4
Q

What is Kw?

A

The equilibrium constant in the water ionization equilibrium; Kw={H30+}{OH-}=1x10-14 at SATP

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5
Q

How else can you study?

A

Go through all examples in textbooks (worked and hmwk)

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6
Q

Why do strong acid reactions have 1 right arrow instead of 1 L/R?

A

Because strong acids react quantitatively with water to form hydronium ions

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7
Q

What separates wa/wb and SA/SB?

A

Not only do SA/SBs react quantitatively with water, they are stronger electrolytes and react faster.

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8
Q

What is implied if entities not found on table are found at last equivalence point?

A

Since these entities can’t affect ph, it must imply any entities that could have been completely consumed, indicating a SA/SB rxn.

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9
Q

What is a Bronsted Lowry acid?

A

A proton donor

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10
Q

What is a bronsted lowry base?

A

A proton acceptor

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11
Q

What is a bronsted-lowry rxn equation?

A

A chemical rxn equation showing an acid-base rxn involving transfer of proton from one entity (acid) to another (base)

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12
Q

What is an amphoteric species?

A

A chemical substance with the ability to react as an acid or base.

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13
Q

What is an amphiprotic species?

A

An entity with the ability to either accept or donate a proton.

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14
Q

Which type of compound will always be amphiprotic?

A

All hydrogen polyatomics are amphoteric since they can both donate a hydrogen ion and accept one.

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15
Q

What is a conjugate acid-base pair?

A

A pair of substances with chemical formulas that differ only by a proton. They appear opposite each other on table.

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16
Q

What should you do when finding sa/sb?

A

Check table for amphiprotic species.

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17
Q

Generalization regarding relative strengths of acid-base conjugate pairs?

A

The stronger an acid, the weaker its conjugate base. Conversely, the weaker an acid, the stronger its conjugate base.

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18
Q

Explain strengths of acids and bases in terms of attraction to hydrogen proton:

A

The stronger an acid, the weaker its attraction to its proton (wants to give it up), and the stronger a base, the stronger its attraction for protons (wants to receive).

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19
Q

What is the strongest acid entity that can exist in a reaction?

A

H3O+. If a stronger acid (6) than hydronium ion is dissolved in water, it reacts instantly and quantitatively to form hydronium ions. 6 SA’s written as H3O+ when in aqueous solution.

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20
Q

What is the strongest base entity that can exist in aqueous solution?

A

OH- is strongest base entity that can exist in aqueous solution. If a stronger base entity than hydroxide ion is dissolved in water, it reacts instantly and quantitatively to form hydroxide ion. (ex: Soluble ionic oxide compounds like Na2O (s) are Na+ and OH- in solution).

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21
Q

Why are the conjugate bases of the 6 SAs not considered bases in aqueous solutions?

A

Because no entity in aqueous solution can react as a base if it is a weaker base than water (H20(l) always present).

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22
Q

What is Ka?

A

The equilibrium constant for the ionization of weak acids. Also known as dissociation constant.

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23
Q

What is ionization?

A

Process by which electrically neutral entities are converted to charged atoms or molecules (ions).

24
Q

What is hydrolysis?

A

Changing the chemical composition of an entity due to reaction with water.

25
Q

What is Kb?

A

The equilibrium constant for the ionization of weak bases. Also known as base dissociation constant.

26
Q

What is a ph curve?

A

A graph showing the change in ph as the volume of titrant increases.

27
Q

What is a buffer?

A

A mixture of a conjugate acid-base pair that maintains a nearly constant ph when diluted or when a SA/SB is added to it.

28
Q

What is a buffer?

A

A mixture of a conjugate acid and its base pair that maintains a nearly constant ph when diluted or when a SA/SB is added to it.

29
Q

Ph of wa/SB rxn:

A

Equivalence point above 7.

30
Q

Ph of SA/SB (see sulfate?) rxn:

A

SA/SBs react quantitatively to form h2o and have an equivalence point at 7.

31
Q

Ph of SA/SB (see sulfate?) rxn:

A

SA/SBs react quantitatively to form h2o and have an equivalence point at 7.

32
Q

What is buffer capacity?

A

The limit of the ability of a buffer to maintain a nearly constant ph.

33
Q

What is another name for acetic acid?

A

Vinegar, or ethanoic acid.

34
Q

Is a scientific concept ever complete?

A

No, this mindset limits further progress in the respective field as this is not usually the case.

35
Q

Why do bronsted-lowry acid-base rxns always have 1:1 ratio?

A

Because they display a transfer of 1 proton between the entities involved.

36
Q

What is another word for inflection point?

A

Midpoint

37
Q

What are indicators, and how are they formed?

A

Indicators are weak acid-base pairs that display different colors in their acid, or base form (depending on ph). They are formed when an indicator dye dissolves in water.

38
Q

What type of molecules are indicators?

A

They are usually complex molecules, because simpler molecules wouldn’t interact with visible light waves?

39
Q

Why is a single arrow used in a titration run?

A

Because reaction in titrations must be quantitative for any stoichiometric equations to be valid (other rxns?).

40
Q

What should you do after finishing a question?

A

Say “I am saying that …(question) implies …” and then ask yourself “Is this logical?” after going over your thought process

41
Q

What should you do after finishing a test?

A

Look it over until the time runs out.

42
Q

What are you suppose to do when a weak polyproctic acid or base is initially dissolved in water?

A

You assume that the ionization equilibrium only involves the first proton transfer-to or from water. This is because the likelihood of an entity formed by a first ionization to lose or gain a second proton is much less than the original entity dissolved (so much so that it can be considered negligible).

43
Q

What is the endpoint of a titration?

A

Actual point in titration where a sudden change is observed (ph or indicator color), thus indicating that the equivalence point has been reached (titrant has completely reacted with sample)

44
Q

What is the equivalence point of a titration?

A

The theoretical volume of titrant that should be added to react completely with sample.

45
Q

What are polyprotic acids?

A

Acids that can lose more than one proton (at least h2).

46
Q

What are polyprotic bases?

A

Bases that can gain more than proton(usually at least -2).

47
Q

What does an equivalence point represent in a ph curve?

A

Each equivalence point represents a proton transfer in a quantitative reaction.

48
Q

How are buffers prepared?

A

By mixing a weak acid with a salt solution of that weak acid.

49
Q

What is the function of H2PO4- and HPO4(2-) in the body?

A

Buffers H2PO4- and conjugate base HPO4(2-) maintain a stabilized ph in the internal fluid of living cells (in cytoplasm).

50
Q

What is the function of H2CO3 and HCO3- in the body?

A

Buffers H2CO3 and its conjugate base HCO3- are mainly responsible for maintaining ph in blood, and most bodily fluids (besides cell cytoplasm).

51
Q

What are some uses of buffers in industry?

A

To avoid side reactions in drug production, maintain ph of dairy products being made, and preserve food.

52
Q

What are sig dig tips for acid-base questions?

A

For ph, all numbers that would normally be sig digs, but ONLY starting after decimal are sig digs. If Ka/Kb values were used in the calculation process use them as sig digs (2).

53
Q

What should you watch out for when given chemical equations?

A

THAT THE EQUATION YOU’VE BEEN GIVEN IS BALANCED.

54
Q

What is another way of explaining what determines the position of an acid-base equilibrium?

A

The competition for proton transfer of the reacting species in the forward direction, and the reacting species in the reverse direction.

55
Q

How to know if an acid/base reaction favours the products?

A

If the proton donor (acid) is higher than the proton acceptor (base) on the table of acid-base strengths, then the products will be favoured.

56
Q

What to remember when finding the ph/poh of a BASE?

A

Use Kb value in calculations (table gives you Ka values), and remember kb=kw/ka. Also in any Kc calculation you can ignore change in concentration if initial concentration is 1000 times greater than Ka/Kb.

57
Q

What is small, yet distinct difference between strong acid and weak acid ph curves?

A

Strong acids go straight from the start, weak acids have small inflection before buffer region.

Chemistry 30 AP (9 decks)

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