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Chemistry OCR A > A2 Acids and Bases > Flashcards

A2 Acids and Bases Flashcards

1
Q

What is a Brønsted–Lowry Acid?

A

A species that donates a proton (H+).

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2
Q

What is an acid base pair?

A

A pair of substances related by the transfer of a proton (H+).

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3
Q

What are Monobasic, Dibasic, and Tribasic Acids?

A

Monobasic Acids - Acids that can donate only one proton (H+).
Dibasic Acids - Acids that can donate two protons (H+).
Tribasic Acids - Acids that can donate three protons (H+).

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4
Q

What is the role of H+ in acid reactions with metals and bases?

A

In acid reactions with metals, H+ ions from the acid react with the metal to form hydrogen gas (H2). In reactions with bases (including carbonates, metal oxides, and alkalis), H+ ions neutralize the base, forming water and salts.

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5
Q

How to convert between ph and [H+]?

A

pH = -log10 [H+]
H+ = 10^-pH

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6
Q

Equation and definition for Kw?

A

Kw = [H+] [OH-]
Kw is the equilibrium constant for the ionization of water into H+ and OH-.

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7
Q

How to calculate the pH for strong acids?

A

pH = -log10 [H+]
To calculate the pH of a strong monobasic acid solution, find the concentration of H+ ions and take the negative logarithm (base 10) of that concentration.

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8
Q

How to calculate the pH of strong bases?

A

For strong bases, use Kw and the concentration of OH- ions to find the pOH. Then, use the equation pH + pOH = 14 to determine the pH.

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9
Q

What is the acid dissociation constant, Ka?

A

Ka measures the extent to which an acid dissociates in water.
Ka = [H+][A-] / [HA]
Higher Ka values indicate stronger acids.

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10
Q

Explain the relationship between Ka and pKa.

A

pKa = -log(Ka)
Lower pKa values indicate stronger acids.
pKa helps in comparing the strength of acids more conveniently.

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11
Q

How to calculate pH and Ka for a weak monobasic acid using approximations?

A

pH = -log[H+], Ka = [H+][A-] / [HA]

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12
Q

Discuss the limitations of using approximations for stronger weak acids.

A

Approximations may not be accurate for acids with higher dissociation.
Deviations occur when the extent of dissociation is significant.

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13
Q

What are pH titration curves and when are they used?

A

pH titration curves show pH changes during an acid-base titration.
Used to determine endpoints, equivalence points, and buffering regions.

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14
Q

Explain the choice of suitable indicators based on pH range.

A

Choose indicators with pKa close to the expected pH at the equivalence point.
Ensures a color change at the endpoint of the titration.

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15
Q

what is the equation to find the concentration of a strong acid?

A

[HA(aq)] = [H+(aq)]

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16
Q

what is the equation to find the concentration of a weak acid?

A

[H+(aq)] = √Ka [HA(aq)]

17
Q

what is the equation to find the concentration of a strong base?

A

[H+(aq)] = Kw / [OH-(aq)]

With 1+ metals [OH-(aq)] = [base(aq)]
With 2+ metals [OH-(aq)] = 2[base(aq

18
Q

what is the equation to find the concentration of a buffer?

A

[H+(aq)] = ka[HA(aq)] / [A-(aq)]

With 1+ metals [A-(aq)] = [salt(aq)]
With 2+ metals [A-(aq)] = 2[salt(aq)]

19
Q

What is a Bronsted-Lowry base defined as?

A

A proton (H+) acceptor

20
Q

What is a conjugate acid-base pair?

A

a conjugate acid-base pair is Two species that can be interconverted by transfer of a proton.

e.g hcl+ h2o = h30+ + cl-
hcl and cl- are conjugate base pairs
h3o+ and h20 and conjugate base pairs

21
Q

In the dissociation of HCl to H+ and Cl-, identify the conjugate acid and base.

A

HCl releases a proton so is therefore the conjugate acid.

Cl- accepts a proton so is therefore the conjugate base.

22
Q

When water is the base, what is formed?

A

H(3)O+

Hydronium ion

23
Q

How can redox reactions be simplified?

A

Remove the spectator ions

24
Q

What is the word equation for the reaction of an acid and a metal? what’s the acronym to remember it?

A

acid + metal -> salt + hydrogen

MASH
metal acid = salt + hydrogen

25
Q

What is the word equation for the reaction of an acid and a carbonate? whats te acronym?

A

acid + carbonate -> salt + water + carbon dioxide

C.A.W.C.S

26
Q

What is the word equation for the reaction of an acid and a base?

A

acid + base -> salt + water

B.A.W.S

27
Q

What is the word equation for the reaction of an acid and an alkali?

A

acid + alkali -> salt + water

A.A.W.S

28
Q

What is the relationship between pH and concentration of H+?

A

Low value [H+] = high pH

High value [H+] = low pH

29
Q

What is the equation for working out pH from [H+]?

A

pH = -log10[H+]

30
Q

How is the pH calculated for a strong acid?

A

Assume it fully dissociates

Therefore [H+] [A-]= [HA] before

31
Q

what equation links pKa and Ka?

A

pKa= -log10 Ka

32
Q

How is the new pH calculated for a strong acid on dilution?

A

Work out change in concentration of HA and therefore [H+]

Then put back into pH = -log[H+]

33
Q

How is the pH calculated for a weak acid?

A

Ka = [H+][A-]/[HA]
Ka[HA] = [H+][A-]
[H+] = [A-]
[H+]^2 = Ka[HA]
[H+] = sqrt(Ka[HA]) then sub in :)

34
Q

what the equation for Kw?

A

Kw= [H+] [OH-]

35
Q

What is Kw?

A

The ionic product of water. water dissociates slightly acting as a weak acid

H20 = H+ + OH-

1X10^-14

36
Q

What is the value of pKw?

A

14.00

37
Q

How can pH of strong bases be found when given the concentration of OH-?

A

pKw (14) = pH + pOH

38
Q

How can pH of weak bases be found when given the concentration of OH-?

A

pKw = pH +pOH

Ka = [H+][A-] / [HA]
Ka[HA] = [H+][A-]
[H+] = [A-]
[A-]^2 = Ka[HA]
[A-] = sqrt(Ka[HA])

39
Q

what are the two assumptions of weak acids?

A

[HA] equilibrium = [HA] undissociated

[H+] = [A-]

Chemistry OCR A (11 decks)

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