A2 Acids and Bases Flashcards
What is a Brønsted–Lowry Acid?
A species that donates a proton (H+).
What is an acid base pair?
A pair of substances related by the transfer of a proton (H+).
What are Monobasic, Dibasic, and Tribasic Acids?
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+).
What is the role of H+ in acid reactions with metals and bases?
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.
How to convert between ph and [H+]?
pH = -log10 [H+]
H+ = 10^-pH
Equation and definition for Kw?
Kw = [H+] [OH-]
Kw is the equilibrium constant for the ionization of water into H+ and OH-.
How to calculate the pH for strong acids?
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.
How to calculate the pH of strong bases?
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.
What is the acid dissociation constant, Ka?
Ka measures the extent to which an acid dissociates in water.
Ka = [H+][A-] / [HA]
Higher Ka values indicate stronger acids.
Explain the relationship between Ka and pKa.
pKa = -log(Ka)
Lower pKa values indicate stronger acids.
pKa helps in comparing the strength of acids more conveniently.
How to calculate pH and Ka for a weak monobasic acid using approximations?
pH = -log[H+], Ka = [H+][A-] / [HA]
Discuss the limitations of using approximations for stronger weak acids.
Approximations may not be accurate for acids with higher dissociation.
Deviations occur when the extent of dissociation is significant.
What are pH titration curves and when are they used?
pH titration curves show pH changes during an acid-base titration.
Used to determine endpoints, equivalence points, and buffering regions.
Explain the choice of suitable indicators based on pH range.
Choose indicators with pKa close to the expected pH at the equivalence point.
Ensures a color change at the endpoint of the titration.
what is the equation to find the concentration of a strong acid?
[HA(aq)] = [H+(aq)]
what is the equation to find the concentration of a weak acid?
[H+(aq)] = √Ka [HA(aq)]
what is the equation to find the concentration of a strong base?
[H+(aq)] = Kw / [OH-(aq)]
With 1+ metals [OH-(aq)] = [base(aq)]
With 2+ metals [OH-(aq)] = 2[base(aq
what is the equation to find the concentration of a buffer?
[H+(aq)] = ka[HA(aq)] / [A-(aq)]
With 1+ metals [A-(aq)] = [salt(aq)]
With 2+ metals [A-(aq)] = 2[salt(aq)]
What is a Bronsted-Lowry base defined as?
A proton (H+) acceptor
What is a conjugate acid-base pair?
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
In the dissociation of HCl to H+ and Cl-, identify the conjugate acid and base.
HCl releases a proton so is therefore the conjugate acid.
Cl- accepts a proton so is therefore the conjugate base.
When water is the base, what is formed?
H(3)O+
Hydronium ion
How can redox reactions be simplified?
Remove the spectator ions
What is the word equation for the reaction of an acid and a metal? what’s the acronym to remember it?
acid + metal -> salt + hydrogen
MASH
metal acid = salt + hydrogen
What is the word equation for the reaction of an acid and a carbonate? whats te acronym?
acid + carbonate -> salt + water + carbon dioxide
C.A.W.C.S
What is the word equation for the reaction of an acid and a base?
acid + base -> salt + water
B.A.W.S
What is the word equation for the reaction of an acid and an alkali?
acid + alkali -> salt + water
A.A.W.S
What is the relationship between pH and concentration of H+?
Low value [H+] = high pH
High value [H+] = low pH
What is the equation for working out pH from [H+]?
pH = -log10[H+]
How is the pH calculated for a strong acid?
Assume it fully dissociates
Therefore [H+] [A-]= [HA] before
what equation links pKa and Ka?
pKa= -log10 Ka
How is the new pH calculated for a strong acid on dilution?
Work out change in concentration of HA and therefore [H+]
Then put back into pH = -log[H+]
How is the pH calculated for a weak acid?
Ka = [H+][A-]/[HA]
Ka[HA] = [H+][A-]
[H+] = [A-]
[H+]^2 = Ka[HA]
[H+] = sqrt(Ka[HA]) then sub in :)
what the equation for Kw?
Kw= [H+] [OH-]
What is Kw?
The ionic product of water. water dissociates slightly acting as a weak acid
H20 = H+ + OH-
1X10^-14
What is the value of pKw?
14.00
How can pH of strong bases be found when given the concentration of OH-?
pKw (14) = pH + pOH
How can pH of weak bases be found when given the concentration of OH-?
pKw = pH +pOH
Ka = [H+][A-] / [HA]
Ka[HA] = [H+][A-]
[H+] = [A-]
[A-]^2 = Ka[HA]
[A-] = sqrt(Ka[HA])
what are the two assumptions of weak acids?
[HA] equilibrium = [HA] undissociated
[H+] = [A-]
