Acids and Bases Flashcards
1
Q
Arrhenius Acid
A
A substance that dissociates in water to produce H⁺ ions
2
Q
Arrhenius base
A
A substance that dissociates in water to produce OH⁻ ions
3
Q
Bronsted Lowry Acid
A
A proton [H⁺] donor
4
Q
Bronsted Lowry Base
A
A proton [H⁺] acceptor
5
Q
Neutralisation
A
The reaction between an acid + a base
forming a salt + water
6
Q
Conjugate Acid
A
formed when a base accepts a proton
7
Q
Conjugate Base
A
formed when an acid donates a proton
8
Q
Conjugate pair
A
an acid + a base that differ by a proton
9
Q
Primary standard
A
Substance of high Mr (Relative Molecular Mass) which can be obtained in a pure stable soluble solid form
- so it can be weighed out
- dissolved in water to give a soln of accurately known conc
10
Q
Titration
A
laboratory procedure where measured vol of one soln is added to a known vol of another soln until reaction is complete
11
Q
pH formula
A
pH = -log[H⁺]
12
Q
Kw
A
Kw = [H⁺] . [OH⁻]
13
Q
[H⁺]
A
[H⁺] = √Kw
14
Q
Strong acid
A
good proton donor
15
Q
Weak acid
A
weak proton donor
16
Q
Strong base
A
good proton acceptor
17
Q
Weak base
A
poor proton acceptor
18
Q
indicator
A
an acid base indicator is a substance that changes colour according to the pH of the soln
19
Q
Methyl orange
A
in acid: red
in base: yellow
range: pH 3-5
20
Q
Phenolphthalein
A
in acid: colourless
in base: pink
range: pH 8-11
21
Q
Litmus
A
in acid: red
in base: blue
range: pH 5-8
22
Q
Indicator for: strong acid/base
A
methyl orange
phenolphthalein
litmus
23
Q
Indicator for: strong acid/weak base
A
methyl orange
24
Q
Indicator for: weak acid/strong base
A
phenolphthalein
25
Indicator for: weak acid/weak base
none
26
Solution
a completely perfect mixture of a solute and solvent, where particles of the solute are uniformly distributed throughout the solven
27
concentration
amount of solute that is dissolved in a given volume of soln
28
molarity
the number of moles of solute per litre of soln
29
No. of moles formula
volume x molarity
/
1000
or
mass / Mr
30
No of moles in diluted and conc soln
[ Vol(dil) x M(dil) ] / 1000 = [ Vol(conc) x M(conc) ] / 1000
31
monobasic acids
an acid which donates one proton per molecule
32
dibasic acids
an acid which donates 2 protons per molecule
33
tribasic acid
an acid which donates 3 protons per molecule
34
Arrhenius theory of an acid
an acid is a substance which dissociates in aqueous soln to form H⁺ ions
HX -> H⁺ + X⁻
35
Limitations to the Arrhenius theory (Acid)
-limited to reactions taking place in water
36
Arrhenius theory of a base
a substance that dissociates in aqueous solution to produce OH⁻ ions
NaOH -> Na⁺ + OH⁻
37
Limitations to the Arrhenius theory (Base)
- limited to reactions taking place in water, other solents like methylbenzene or liquid ammonia were exceptions
- substances such as NH₃ would not be classified as bases (Do not prod. OH⁻ ions)
38
How an acid would react with a base according ot Arrhenius theory
- In soln, acid molecules dissociates + forms H⁺ ions
- Base molecules dissociates + forms OH⁻ ions
- H⁺ ions + OH⁻ ions react and form H₂O
39
Neutralisation reaction
one in which an acid and a base react to form a salt and water
40
standard soln
soln whose conc is accurately known
41
Primary standard criteria
- highly pure state
- stable in air
- dissolve easily in water
- fairly high relative molecular mass
- should undergo complete + rapid reaction
- must be anhydrous
42
primary standard eg
sodium chloride NaCl
| anhydrous sodium carbonte Na₂CO₃
43
equivalence point
stage when two solns just react completely with each other
44
end point
when the equivalence point is shown by an indicator
45
titration
a lab procedure where a measured vol of one soln is added to a known vol of another soln until reaction is complete
46
apparatus used in vol analysis
```
grad cylinder
volumetric flask
pipette
burette
conical flask
```
47
Bronsted-Lowry theory of an acid + advantage of theory
- an acid is a proton donor (H+) therefore a strong acid is a strong proton donor
- A base is a proton acceptor
advantage: does not just deal w/ reactions in water
48
conjugate base
species formed when an acid has donated a proton
49
strong acid
- an acid which dissociates fully into ions in an aqueous soln
- every HCl molecule breaks up into ions
50
weak acid
- an acid which only slightly dissociates into ions in an aqueous soln
- very few of these acid molecules dissociates or beak up into ions
51
why is H2SO4 a strong acid?
- fully dissociates into ions when in an aqueous soln
| - has great tendency to break/give protons
52
why strong acids form weak conjugate bases
H₂SO₄ -> HSO₄ (strong acid -> weak conj. base)
- a strong acid such as sulphuric acid readily donates a proton and forms a conj base HSO₄
- conj base is a weak base as it does not readily accept a proton
53
show that conjugate base H2SO4 can itself act as an acid
H₂SO₄ loses a proton + forms the conjugate base HSO₄⁻
54
conjugate base
an acid changes into its conjugate base when it donates a proton
55
conjugate acid
a base changes into its conjugate acid when it accepts a proton
56
Conjugate acid/bond pair
2 substances which differ by an H+ or a proton
57
atmospheric substances
a substance which can behave as an acid or base depending on what it reacts with
58
acidity
acidity of a soln depends on the conc of H+ ions in the soln
59
Bronsted Lowry's conjugate pair
any pair consisting of an acid and base that differ by H+ or a proton
60
Limitation of the pH scale
- limited to 0-14 range even tho pH values outside range are possible (in theory)
- does not work w/ very conc solns
- limited to aqueous solns, chemical reactions can occur in other types of soln
61
self ionisation of water
2H₂O ⇌ H₃O⁺ + OH⁻
62
Kc expression
[H⁺][OH⁻]/[H₂O]
63
Why is NH₃ considered to be a base according to Bronsted-Lowry theory?
NH₃ accepts a proton (H⁺)
64
Ka expression
[H⁺][A⁻]/[HA]
65
Kb expression
[BH⁺][OH⁻]/[B]
66
Ka
Ka = (10⁻ᵖᴴ)²/Mₐ
67
pH using Ka
pH = √(Ka)[HA]
| =
68
essential property of an indicator used to edetect the end point in a titration between acid and base and their pH curve
Changes colour between Phs with straight line in graph
69
define pH
pH = -log₁₀[H⁺]
negative log to base ten of hydrogen (hydronium) ion concetration
70
pH curve general shape
know general shape
71
explain your selection of indicator for a titration with reference to your pH curve
colour change (indicator range) coincides with sharp rise on graph
72
pH using Kb
pH = √(Kb)(M)
73
Define Kw (the ionic product of water)
Kw = [H⁺][OH⁻]
/ Kw = [H₃O⁺][OH⁻]
Product of molar concentrations of hydrogen (hydronium) ions (H⁺, H₃O⁺) and hydroxide (hydroxyl) ions (OH⁻) in water
74
Vinegar experiment - why was the vinegar diluted?
- Vinegar too concentrated, would require very concentrated (NaOH) solution / very large volume of NaOH needed to get a reasonable titration.
- Small titration volume lowers accuracy and increases percentage error
75
Describe the correct procedures for measuring exactly an amount of vinegar and diluting it using deionised water
- Rinse pipette with deionised water and then vinegar
- fill with pipette filler to amount, taking meniscus into account (have bottom of meniscus on mark), read at eye level (Vertically)
- deliver to volumetric flask
- add deionised water until level of water near mark
- add dropwise by dropper and bring bottom of meniscus to mark (at eye level)
- stopper and invert several times
76
make use of your pH graph to deduce the volume of base required for neutralisation
find volume where line is straight
77
Is Chloric(I) acid strong or weak? Give a reason for your answer
weak, as low dissociation constant
78
explain how an acid-base indicator, which is itself a weak acid and is represented by HX, functions
-the indicator intself dissociates according to the equation HX ⇌ H⁺ + X⁻
- In base, equilibrium lies on right giving colour of X⁻ ion
- In acid equilibrium lies on left, giving colour of HX molecule
79
A certain water soluble indicator represented by HIn is a weak acid which dissociates as follows in water:
HIn (green) ⇌ H⁺ + In⁻ (purple)
State and explain the colour observed when a few drops of a solution of the indicator are aded to a 0.5M NaOh solution
purple
-hydroxyl ions (OH⁻) remove hydrogen ions (H⁺) causing the reaction to shift to the right
80
explain, by giving a balanced equation for its dissociation in water that the conjugate base of sulfuric acid is itself an acid
HSO₄⁻ + H₂O --> SO₄²⁻
| + H₃O⁺
81
- what compound in white whine is converted to ethanoic acid in vinegar?
- what type of chemical process converts this to ethanoic acid?
- ethanol
| - oxidation
82
conjugate acid of H2O
H₃O⁺
| hydronium ion
83
in terms of hydrogen ions, account for the difference in pH values between x and y
Just use the pH formula, put both of their M into pH formula and label which is which's pH
eg.
pH HCl = -log(0.10) = 1.00
while pH H2SO4 = -log(0.10) = 0.70
or answer:
0. 10M HCl produces 0.10M H+ ion (monobasic)
0. 10M H2SO4 produces 0.20M H+ ion (dibasic)
HCOOH is a weak acid/poor proton donor/weaker than X
84
Methanoic acid formula
HCOOH
85
using graph to find volume needed for neutralisation
the volume where there is the steepest/straight rise in graph/curve
86
identify two substances acting as base in this equilibrium
read question carefully, identify the two bases not the acid and base
87
calculate the conc of H+ ion in nitrous acid and explain how this confirms that it is a weak acid
find conc in mol/L, then say
| "Ka of nitrous acid is only x" (use it to find Ka)
88
conc of H+ ion in HNO2 (nitrous acid) is 0.01, what conc of nitric acid (HNO3) would have the same H+ ion concentration?
Since nitric acid is a strong acid, [HNO3] = [H30+],
| so conc = 0.01 mol/L
89
common strong acids and bases
learn off some
90
calculate the pH of NH4OH
its a base so use pOH to get pH!
91
A certain water soluble acid-base indicator represented by HIn is a waek acid which dissociates as follows in water....
(2012 q10b)
state and explain colour observed when a few drops of a solution of the indicator is added
purple
hydroxyl ions/OH- remove hydrogen ions (H+) causing the reaction/equilibrium to shift to the right
92
which of the conjugate bases of these is stronger? Sulfuric acid conj base or the conj base of a weak acid HA? + why
A- (the conjugate base of the weak acid)
it is a conjugate base of a weak acid /A- more likely to accept a proton
93
name a suitable indicator for titration between ethanoic acid and NaOH
state colour change
phenolphthalein bc its a titration of a weak acid and strong base
colour change: pink to colourless
94
conjugate base of H2O
OH- (not HO-)
95
an indicator changes in the pH range 7.6-9.2 for which types of acid-base titrations would it be suitable?
strong acid-strong base
and
weak acid-strong base
96
Ka of Chloric(I) acis is 3.7x10^-8 is it a strong acid or weak and why
weak as it has low Ka
97
calculate approx percentage dissociation of x
Use Ka and equilibrium ICE thing to find conc of [H+]. Then put this value over the molarity (mol/L or mol/dm3) and multiply by 100 to get percentage
OR
-use [H+] = √Ka x Ma , then put [H+] over molarity and multiply by 100 to get percentage
98
pH curve of weak acid and strong base
- steep rise at vol of NaOh that equals vol of acid
- vertical rise mostly above pH of 7
- pH starts at original pH of acid
- label axes, pH axis is 0-14
99
calculate the molarity/concentration of sulfuric acid
get the inverse log, then divide the answer by two to get the conc of H+ ions as sulfuric acid (H2SO4) is dibasic and you want the conc of H+ ions
100
with reference to pH graph, why is any indicator suitable for this reaction (strong acid and strong base)
most indicators with change around this range
101
calculating water of crystallisation
- Find Mol/L of x, then turn it into mol/vol of original solution first before finding the no. of grams of x.
- Take away grams of x from grams of crystal to get grams of water
- find no of moles of x (using Mr of x) and then no of moles of H2O (using Mr of H2O)
- divide
102
H2F+ + Cl - --> HCl + HF
identify an acid and its conjugate base
H2F+ and HF
103
[H+], Ka, and M
[H+] = √Ka.M
