Acids and bases Flashcards
What is an acid?
are compounds which can act as proton donors (i.e. they can give a proton, H+ to another compound).
What is an Base?
are compounds which can act as proton acceptors (i.e. they can accept a proton,
H+ from another compound).
What is an acid-base reaction?
involves the transfer of a single proton from one species to another.
A Brønsted–Lowry acid will donate a proton to a Brønsted–Lowry base.
What is an acidic proton?
- For a proton to be considered acidic, it must
be bound to another atom via an acidic bond. - Acids have a H-atom attached to an electronegative atom, making a polar bond.
- Acids tend to contain protons bound to group
16 or 17 elements.
What do basic species require?
Basic species require the presence of one or more lone pairs of electrons.
Not all species containing lone pairs act as bases.
What groups do bases usually contain?
Groups 15 or 16 elements - the atoms of which are often deprotonated
What are conjugate acid-base pairs?
For Brønsted–Lowry acid-base reactions both the forward and reverse reactions are acid-base reactions.
when we have an acid, we always have a base
What is a monoprotic acid and base?
an acid that can donate only a single proton.
a base that can accept only one proton.
What is a diprotic acid?
an acid that can potentially donate two protons.
a base that can accept two protons.
What is polyprotic?
an acid that can donate more than one proton.
a base that can accept more than one proton.
What is neutralisation?
the reaction of an acid and base called neutralisation reaction
The one counteracts the action of the other
acid and a base results in a salt and water
What is amphoteric?
a compound that can act both as an acid and a base
Water can act as both an acid and a base (proton donor and acceptor) - amphoteric
depends on the conditions
Are amino acids amphoteric?
Yes, compounds of protein
Can water react with itself, if so, explain?
Yes, reacts with itself - known as autoprotolysis of water.
water is neutral - no charge at 25 degrees.
Water reacts giving H3O+ hydronium ions and OH- hydroxide ion
What is a water constant?
1.0 x 10^-14
What is the basic principle of acid base chemistry in regards to the inverse relationship between H3O+ and OH-?
if you have more hydronium ions (H3O+) then you have more acidic aqueous solutions.
However, if you have more OH+ hydroxide than, hydronium ions, you have a more basic (alkaline solution)
What is pH?
pH indicates the concentration of hydrogen ions (H+) in the solution
applies to acids
pH = -log[H+]
[H3O+] = 10^-pH
What is pOH? and the formula to find pOH as well as reverse
indicates the concentration of hydroxide ions (OH-) in the solution
pOH = -log [OH-]
[OH-] = 10^-pOH
applies to bases
What does pH + POH equal together?
14
What does neutral ph mean?
scaled at a pH of 7 = equal concentration of protons and hydroxide ions
What does < 7 mean?
the solution is acidic (more proton than hydroxide ions)
What does >7 mean?
the solution is basic (more hydroxide ions than protons?
What is a strong acid?
reacts completely with water to give quantitative formation of protons (H3O+)
What is a weak acids?
reacts incompletely with water to form less than stoichiometric amounts of protons (H3O+)
What is an acid dissociation constant - Ka
Distinguish and compare which acid is stronger between two or more acids. The higher the Ka, the stronger the acid
What is the difference between strong and weak acid?
weak acids ionize partially - creating an equilibrium between the dissociated form and before dissociation (lies to the left for weak acid)
What is the acid/base dissociation constant good for?
The size of the acid dissociation constant allows you to compare the
strengths of different weak acids.`
What does a buffer solution do ?
A buffer solution resists change in pH after the addition of small amounts of
either acid or base, and also on moderate dilution.
what is generally contained within a buffer solution?
A buffer solution is one that contains appreciable amounts of both a weak acid and its
conjugate base, or a weak base and its conjugate acid.
Buffers cannot be prepared with strong acids or bases as they are too reactive.
What ph is a buffer?
pH range over which a buffer is effective is determined by either pKa or pKb and the ratio of the conjugate pairs present in the solution
How do buffers function?
The common ion effect
If you add the salt of a weak acid to the solution of the same acid then the equilibrium will shift
towards neutral pH.
Following Le Châtelier’s principle, the equilibrium will shift to the left, lowering the concentration
of H3O+ and increasing pH.
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The same is true for a base: if you add the salt of a weak base to a solution of the same base then the equilibrium will shift towards lower pH
Any added acid (H3O+) or base (OH-) will react with
conjugate base (A-) or weak acid (HA) in solution.
Thus resisting a change in pH.
N.B. M+ is a spectator ion
What are titrations?
A titration is a method for finding the concentration of a set volume of a solution of unknown concentration by reacting it with a solution of known concentration. The volume added is measured from a burette – a long glass column with volume markings and a tap on the bottom.
What is titrant
the reagent solution of precisely known concentration that is being added (i.e. what’s in the burette)
What is the end point
the point (or volume) in a titration where reaction is complete and a change in an indicator is first observed.
What is the equivalence point
where an equivalent number of moles of titrant is added to that in the solution being analysed, as required by the balanced reaction
equation.
