Acid & Base

Question 1

monobasic or monoprotic / dibasic or diprotic / tribasic or triprotic

Answer 1

HCl is termed a monobasic or monoprotic acid because it releases ONE H+ ion on
dissociation.
Sulphuric acid (H2SO4) is diprotic.

Question 2

Arrhenius Theory definition of acids & bases

Answer 2

substances which ionise or dissociate in aqueous solution to produce H+ (aq ions (i.e. protons).
Defined bases as substances which ionise or dissociate in aqueous solution to produce OH- (aq) ions.
E.g. For HCl —in pure form this is a covalent substance and a gas at room temperature and pressure — but when dissolved in water HCl molecules dissociate into H+ ions and Cl ions.

Question 3

Bronsted-Lowry definition of acids and bases

Answer 3

Acids as Proton (H+) donors
Bases as Proton acceptors

Question 4

What is a conjugate acid/base pair using HCI as an example

Answer 4

Pair of species that differ by one proton. The base can accept a proton to form the acid and the acid lose protons to become the base. E.g. HCl (acid) Cl- (base)

Question 5

relative strengths of members of conjugate acid/base pairs, again using HCI as an example

Answer 5

Strong acids have weak conjugate bases (and vice versa). HCl has strong tendency to donate protons: it is a strong acid. The Cl- ion has poor ability to accept protons: it is a weak base.

Question 6

what is the name of the H30 + ion

Answer 6

hydronium ion

Question 7

Answer 7

Water acts both as an acid and a base. It is said to be amphoteric

Question 8

Lewis Theory of Acids and Bases

Answer 8

Lewis red-defined acids/bases as:-
e An acid is an electron pair acceptor.
e A base is an electron pair donor

Question 9

amphoteric substances

Answer 9

Question 10

Kw

Answer 10

as temperature increases, Kw increases

Question 11

Effect of temperature on ph of a solution

Answer 11

Question 12

STRONG / weak ACIDS

Answer 12

STRONG acids:
VERY high proportion of molecules dissociate in solution
weak acids:
SMALL proportion of molecules dissociate in solution.

Question 13

eqn relating PH & [H+]

Answer 13

[H+] = 10^-pH
pH = - log( [H+] )

Question 14

Answer 14

Question 15

Answer 15

Question 16

Ka

Answer 16

as a increases, Ka increases, Acid strength increases

Question 17

Ka calculation example

Answer 17

Question 18

buffer solutions - how do acid buffers work

Answer 18

effect of adding acid H+ ions:
CHCOO- + H+ -> CH3COOH

effect of adding base (OH-) ions:
CH3COOH + OH- > CH3COO- + H2O

Question 19

basic buffer solutions

Answer 19

Question 20

Calculations involving buffer solutions compared to weak acid calculations

Answer 20

Question 21

Answer 21

Question 22

PH curves and their types

Answer 22

Question 23

Definition Of terms to be aware of :-
Equivalence Point

Answer 23

Point at which the correct number of moles of acid/base have been added to react completely with the base/acid.

Question 24

Definition Of terms to be aware of :-
End Point

Answer 24

Point at which the indicator changes colour in a titration.

Question 25

Definition Of terms to be aware of :- pH range, initial PH, final PH

Answer 25

pH range - Range of ph values covered by the near vertical section of the pH curve. initial PH - pH at the start of a titration final PH - pH at the end of a titration

Question 26

ph curves - strong acid vs strong base - initial / final PH, PH range, PH at equivalence point, shape of graph

Answer 26

Question 27

ph curves - weak acid vs strong base - initial / final PH, PH range, PH at equivalence point, shape of graph

Answer 27

Question 28

ph curves - strong acid vs weak base - initial / final PH, PH range, PH at equivalence point, shape of graph

Answer 28

Question 29

ph curves - weak acid vs weak base - initial / final PH, PH range, PH at equivalence point, shape of graph

Answer 29

Question 30

calculating Ka of acids from titration curves

Answer 30

Question 31

how do indicators work - methyl orange and phenolphthalein

Answer 31

Question 32

indicators and PH range

Answer 32

Indicators need to change colour over a narrow PH range if they are to be useful. If an indicator is be effective in a titration its colour must change abruptly near the equivalence point of a titration. For this to happen the pH range of the indicator must co-incide with the near-vertical part of the pH curve so that a very small addition of titrant near the equivalence point gives a very large change in pH.