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MCAT gen chem > Acids and bases > Flashcards

Acids and bases Flashcards

1
Q

What are the three definitions for acid and bases?

A
  1. Arrhenius
  2. Bronsted-Lowry
  3. Lewis
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2
Q

What is the Arrhenius definition of acid-base?

A

Acid- will dissociate to form an excess H+ in solution
Base- Will dissociate to form an excess of OH- in solution
This is limited to aqueous acids and bases. they usually contain H in the beginning or OH at the end.

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3
Q

What a bronsted Lowry acid and base?

A

Acid- A species that donates H+ ions
Base- species that accepts H+ ions
It is not limited to aqueous solutions.
Usually occurs in pairs, called conjugate acid-base pairs

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4
Q

What is the Lewis acid-base definition?

A

Acid- an electron pair acceptor.
Base- electron pair donor
Different Names:
coordinate covalent bond formation, complex ion formation, nucleophile-electrophile interactions.

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5
Q

What are amphoteric species?

A

One that reacts like an acid in a basic environment and like a base in acidic environments.

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6
Q

What is an amphiprotic species?

A

In a Bronsted-Lowry, it can gain or lose a proton .

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7
Q

What are some amphoteric species?

A

Water, HSO4- also note Al, Zn, Pb, Cr, Zwitterions .

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8
Q

If an acid is formed from anions with names that end in -ide, the nomenclature is ?

A

Prefix hydro, ending ic

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9
Q

Oxyacids that end in -ite or ic have a nomenclature of?

A

end in -ous acid or ic acid respectively.

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10
Q

what is Autoionization?

A

When an amphoteric compound reacts with itself, like water.

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11
Q

What is Kw?

A

It is the water dissociation constant Kw= 10^-14. OH and H ions each 10^-7 if perfectly pure water

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12
Q

What is the equation for pH and pOH

A

pH= -log[H+]= log 1/[h+]

pOH=-log [OH-]= log 1/[OH-]

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13
Q

Concept understanding. -log( n x 10^-m) =

A

-log(n)-log(10^-m) = m - log(n), p value around m-0.n

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14
Q

What are strong acid and bases?

A

they completely dissociate in their component ions in aqueous solutions. They go to completion.

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15
Q

If the concentration of an acid or base is not far greater than 10^-7, what must one consider?

A

Autoionization of water. It is not negligible at this point (note ex on pg 339).

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16
Q

What are some strong acids?

A

HCl, Hbr, HI, H2SO4, HNO3, HClO4

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17
Q

What are some strong bases?

A

NaOH, KOH, soluble hydroxides of group IA.

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18
Q

What does it mean when a pH of a solution is greater than 14 or less than 0?

A

this implies there is a very high concentration of strong acids or bases.

19
Q

What is the definition of weak acids and strong bases?

A

They partially dissociate in aq solutions.

20
Q

What is the acid dissociation constant?

A

Ka = [H2O+][A-]/[HA] . the smaller Ka, the weaker the acid. Less than 1 is a weak acid

21
Q

What is the base dissociation constant?

A

Kb = [B+][OH-]/[BOH] . the smaller b, the weaker the base and the less it will dissociate. less than one is a weak base.

22
Q

How can the dissociation constant be determined if one species or conjugate is known.

A

Ka acid x Kb conjugate = Kw (10^-14) . vice versa too

23
Q

When is approximation of x valid?

A

when x is less than 5% of the initial concentration or Ka is 100 times smaller.

24
Q

What is neutralization reaction?

A

Acids and bases may react with each other to forma salt and often water(but not always). in general it is a process that goes to completion.

25
Q

What is hydrolysis?

A

When salt ions react with water to give back the acid or base.

26
Q

What occurs between a strong acid and strong base?

A

Products form equal molar amounts of the salt and base. They also neutralize each other and result in a pH of 7. They do not react with water because they are inert conjugates.

27
Q

What happens when a weak base and strong acid react?

A

A salt is formed but often no water will be formed because weak bases are not hydroxides. The weak base can be reformed through hydrolysis.

28
Q

What happens when a weak base and acid react ?

A

Depends on the relative strength of each, can go either way of the spectrum.

29
Q

What is the the equation to calculate unknown titrand?

A

NaVa =NbVb . normality and volume.

30
Q

What is the Henderson Hasselbalch equation

A

used to estimate pH or pOH of a buffer solution
pH=pKa + log [A]/[HA] . When conjugate base = weak acid, pH= pKa cause log 1 is 0. This occurs at half equivalence and is optimal. It quantifies the relationship between pH and pKa and vice versa.

31
Q

How do you calculate the pH of a buffer when acid or base is added?

A

Calculate the the concentration in the final solution, NV=NV, then use the henderson equation.

32
Q

What is equivalent?

A

It is defined as one mole of the species of interest .

33
Q

What is normality?

A

The concentration of acid or base in equivalents solution.

34
Q

What is polyvalent?

A

acid and base are those that can donate or accept multiple electrons. The normality of a solution containing polyvalent species is the molarity of the acid or base times the number of protons it can donate or accept.

35
Q

What are titrations?

A

they are used to determine the concentration of a known reactant in a solution.

36
Q

What is a titrant?

A

the concentration that is added slowly to the titrand

37
Q

What is the titrand?

A

an unknown concentration but a known volume

38
Q

What is the half-equivalence point?

A

it is the midpoint of the buffering region, in which half of the titrant has been protonated, or deprotonated. Thus HA=A- and buffer is formed

39
Q

What is the equivalence point?

A

indicated by the sleepes slope in a atitration curve, it is reached when the number of acid equivalents in the original solution equals the number of base equivalents acid, or vice versa.

40
Q

What are indicators?

A

they are weak acids or bases that display different colors in their protonated or deprotonated states. The indicator chosen should have a pKa close to the pH of the expected equivalence point. the endpoint of a titration is when the indicator reaches its final color.

41
Q

If multiple buffering regions are observed, then …

A

it is polyvalent.

42
Q

What are buffer solutions?

A

Consist of a mixture of a weak acid and its conjugate salt or vice versa, they resist large fluctuations in pH.

43
Q

What are buffering capacities?

A

refers the ability of a buffer to resist changes in pH. Maximal buffering capacity is seen within 1 pH point of the pKa of the acid in the buffer solution.

MCAT gen chem (11 decks)

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