Acids and bases

Question 1

What is an acid?

Answer 1

are compounds which can act as proton donors (i.e. they can give a proton, H+ to another compound).

Question 2

What is an Base?

Answer 2

are compounds which can act as proton acceptors (i.e. they can accept a proton,
H+ from another compound).

Question 3

What is an acid-base reaction?

Answer 3

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.

Question 4

What is an acidic proton?

Answer 4

• 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.

Question 5

What do basic species require?

Answer 5

Basic species require the presence of one or more lone pairs of electrons.

Not all species containing lone pairs act as bases.

Question 6

What groups do bases usually contain?

Answer 6

Groups 15 or 16 elements - the atoms of which are often deprotonated

Question 7

What are conjugate acid-base pairs?

Answer 7

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

Question 8

What is a monoprotic acid and base?

Answer 8

an acid that can donate only a single proton.

a base that can accept only one proton.

Question 9

What is a diprotic acid?

Answer 9

an acid that can potentially donate two protons.
a base that can accept two protons.

Question 10

What is polyprotic?

Answer 10

an acid that can donate more than one proton.
a base that can accept more than one proton.

Question 11

What is neutralisation?

Answer 11

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

Question 12

What is amphoteric?

Answer 12

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

Question 13

Are amino acids amphoteric?

Answer 13

Yes, compounds of protein

Question 14

Can water react with itself, if so, explain?

Answer 14

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

Question 15

What is a water constant?

Answer 15

1.0 x 10^-14

Question 16

What is the basic principle of acid base chemistry in regards to the inverse relationship between H3O+ and OH-?

Answer 16

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)

Question 17

What is pH?

Answer 17

pH indicates the concentration of hydrogen ions (H+) in the solution

applies to acids

pH = -log[H+]
[H3O+] = 10^-pH

Question 18

What is pOH? and the formula to find pOH as well as reverse

Answer 18

indicates the concentration of hydroxide ions (OH-) in the solution

pOH = -log [OH-]
[OH-] = 10^-pOH
applies to bases

Question 19

What does pH + POH equal together?

Answer 19

14

Question 20

What does neutral ph mean?

Answer 20

scaled at a pH of 7 = equal concentration of protons and hydroxide ions

Question 21

What does < 7 mean?

Answer 21

the solution is acidic (more proton than hydroxide ions)

Question 22

What does >7 mean?

Answer 22

the solution is basic (more hydroxide ions than protons?

Question 23

What is a strong acid?

Answer 23

reacts completely with water to give quantitative formation of protons (H3O+)

Question 24

What is a weak acids?

Answer 24

reacts incompletely with water to form less than stoichiometric amounts of protons (H3O+)

Question 25

What is an acid dissociation constant - Ka

Answer 25

Distinguish and compare which acid is stronger between two or more acids. The higher the Ka, the stronger the acid

Question 26

What is the difference between strong and weak acid?

Answer 26

weak acids ionize partially - creating an equilibrium between the dissociated form and before dissociation (lies to the left for weak acid)

Question 27

What is the acid/base dissociation constant good for?

Answer 27

The size of the acid dissociation constant allows you to compare the
strengths of different weak acids.`

Question 28

What does a buffer solution do ?

Answer 28

A buffer solution resists change in pH after the addition of small amounts of
either acid or base, and also on moderate dilution.

Question 29

what is generally contained within a buffer solution?

Answer 29

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.

Question 30

What ph is a buffer?

Answer 30

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

Question 31

How do buffers function?

Answer 31

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.
*

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

Question 32

What are titrations?

Answer 32

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.

Question 33

What is titrant

Answer 33

the reagent solution of precisely known concentration that is being added (i.e. what’s in the burette)

Question 34

What is the end point

Answer 34

the point (or volume) in a titration where reaction is complete and a change in an indicator is first observed.

Question 35

What is the equivalence point

Answer 35

where an equivalent number of moles of titrant is added to that in the solution being analysed, as required by the balanced reaction
equation.