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Chem110: Term 2 > Block 5: Acids And Bases > Flashcards

Block 5: Acids And Bases Flashcards

1
Q

Happens when an acid and alkali neutralise each other?

A

They form a salt and water (called a base) to

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2
Q

What does pH equal?

A

-log10 [H3O]

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3
Q

What is a neutral pH?

A

7

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4
Q

How do we calculate the concentration of H3O?

A

[H3O]= 10^-pH

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5
Q

Equation to calculate the concentration of H3O in a solution of HBr, pH 2.77?

A

[H3O] = 10^-2.77

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6
Q

Drawbacks of Arrhenius theory on salts?

A

Only works for substances dissolving in water
Doesn’t explain why some compounds containing H (like HCl) are acids, while others (like CH4) are not
Doesn’t explain why some compounds without OH can act as bases

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7
Q

What donates a proton?

A

Acids

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8
Q

What accepts a proton?

A

Bases

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9
Q

What’s the Bronsted equation?

A

HCl(aq)+ H2O (l) to H3O (aq) + Cl- (l)

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10
Q

What is the species that is left behind after a bronsted acid has transferred its proton called?

A

The conjugate base of the acid

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11
Q

What is the species that is formed after a Bronsted base has accepted a proton called?

A

The conjugate acid of the base

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12
Q

What is amphiprotic?

A

A species (like H2O) that can be an acid and a base

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13
Q

What happens if an acid can donate more than one proton (eg sulfuric acid H2SO4, phosphoric acid H3PO4)?

A

It’s show in two or more steps

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14
Q

When is there a position of equilibrium?

A

In proton transfer reactions

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15
Q

What is the equilibrium constant K equation?

A

HA(aq)+H2O(l) to A-(aq)+H3O (aq)

To

K= [A-(aq) x [H3O(aq)]/ [HA (aq)]

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16
Q

What is the standard concentration for species dissolved in solution?

A

1 mol L-1 (ie 0.1)

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17
Q

What is the proton transfer equilibrium constant and how is it calculated?

A

Ka

Same as K

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18
Q

What has a larger equilibrium constant?

A

Stronger acids

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19
Q

What is PKa?

A

-log10(Ka)

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20
Q

What has a smaller PKa?

A

Stronger acid

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21
Q

What would a Ka be for a species that appears on both sides?

A

1 (as it appears on both sides)

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22
Q

What affects the strength of an acid?

A
  1. The charge on A
  2. The polarity of the H-A bond
  3. The strength of the H-A bond

(Strength of bond is more important than strength of electronegativity)

23
Q

What are oxoacids?

A

H3PO3 or H2SO4, when. It all the acids are necessarily acidic

24
Q

What is Fw (equilibrium constant for water)?

A

Kw= [H3O(aq)]x[OH-(aq)]

25
Q

What is the concentration of H3O in a solution of a strong acid?

A

0.01mol L-1 (as the acid is 100% dissociated (but needs to not be dilute)

26
Q

How do you calculate the concentration of OH- for a strong base?

A

Calculate the concentration of OH-, then use Kw to get the concentration of H3O

27
Q

When is the equilibrium not always all the way to the right?

A

Weak acids, where not all the acid is converted to H3O

28
Q

Ka equation for solutions containing a weak acid and its conjugate base?

A

Ka = [A- (aq)] x [H3O(aq)]/[HA(aq)]

29
Q

What is the pH of a solution containing a weak acid and its conjugate base?

A

pH= pKa + log10 {A-/ HA}

Called a Henderson-hasselbach equation

30
Q

What is a titration?

A

A method of volumetric analysis used for determining the concentration pH an unknown solution by letting it react with another whose concentration is known

31
Q

What is the equivalence point?

A

The volume at which the reaction is just completed

32
Q

What is the concentration equation?

A

Amount= concentration x volume

N= c x v

33
Q

What happens at the equivalence point in an acid/base titration?

A

The pH of solution changes rapidly

34
Q

What is an indicator?

A

A substance that has different colours in acid and basic solution

35
Q

What is the end point for the indicator?

A

The pH at which the colour change occurs (useful if the same as equivalence point)

36
Q

What happens when a strong acid and base undergo a titration?

A

They’re both 100% dissociated

37
Q

What is an indicator’s properties?

A

A weak acid, for which the acid and its conjugated base have different colours

38
Q

Acidity constant equation for an indicator?

A

Kln = [ln-(aq)]x[H3O(aq)] / [HIn(aq)]

39
Q

Equivalence point of a strong acid and a strong base?

A

7

40
Q

Why do the acid and conjugate base forms have different colours?

A

Because of the extent of electron delocalisation difference of the two forms

41
Q

What does the pH of an equivalence point in a titration depend on?

A

The acid (eg, a weak acid has a high pH)

42
Q

What is that equation for pH in a weak acid/base titration?

A

pH= 7 + (1/2xpKa) + (1/2xlog10(c))

pKa is of the weak acid, and c is the concentration of the conjugate base at the equivalence point

43
Q

Where is the acid and conjugate base equal to each other for a titration?

A

At volume halfway to the equivalence point, so, at this point, pH is equal to pKa

44
Q

What is polyprotic?

A

Species capable of donating more than one proton (eg H2SO4)

45
Q

For polyprotic species, which proton loss is easier?

A

The loss of the second proton

46
Q

What is a buffer solution?

A

A solution whose pH changes much less than that of pure water as we add either acid or base

47
Q

What does a buffer solution contain?

A

Either equal amounts of a weak acid and its conjugate base (if pH lower than 7) or a weak base and its conjugate acid (is pH is higher than 7)

48
Q

Why can a buffer work?

A

Because it contains species that both accept and donate proteins

49
Q

What does the pH change by in a buffer solution?

A

Only +1 unit or -1 unit

50
Q

What makes a buffer solution more effective?

A

When there is a higher concentration of the two species

51
Q

What is the human body buffer system like?

A

More conjugate base than acid, as likely waste products from the body are largely acidic

52
Q

What does a raised pH in the body cause?

A

Light headedness

53
Q

What is the pH at which the majority of species are zwitterions called?

A

The isoelectric point, which is denoted by pI, and depends on the relative strength of the acidic and basic parts of the molecule, and varies between amino acids

54
Q

What is electrophoresis?

A

A technique which separates mixtures of amino acids

Chem110: Term 2 (3 decks)

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