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Chemistry Ib > Chapter 8 > Flashcards

Chapter 8 Flashcards

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1
Q
A

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2
Q

8.1 Define Bronsted-
Lowry acids and
bases.

A

A Bronsted-Lowry acid is a proton/H+ donor and
a Bronsted-Lowry base is a proton/H+ acceptor.

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3
Q

8.1 Distinguish the
difference between
amphiprotic and
amphoteric species.

A

Amphiprotic species can act as both Bronsted-
Lowry acids and bases.
All amphiprotic species are amphoteric, but not
all amphoteric species are amphiprotic.
**amphiprotic applies to Bronsted-Lowry acids
and bases only.
amphoteric: can act as both acid and base
amphiprotic: can act as both H+ proton donor and
receiver

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4
Q

8.1 Define conjugate
acid-base pair.

A

A pair of species differing by a single proton
e.g
H20 and H3O+
NH3 and NH4+

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5
Q

8.1 How is the
presence of proton
is represented in
aqueous solution?

A

Students should know the representation of a
proton in aqueous solution as both H+ (aq)and
H3O+ (ag)

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6
Q

8.1 List the chemical
formula for the
following acids.
hydrochloric acid
nitric acid
sulfuric acid
ethanoic acid
carbonic acid
phosphoric acid
benzoic acid

A

HCl
HNO3
H2S04
CH3COOH
H2C03
H3PO4
C6H5COOH

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7
Q

8.1 List the chemical
formula for the
following bases.
calcium oxide
copper (Il) oxide
sodium hydroxide
lithium hydroxide
calcium hydroxide
barium hydroxide
ammonia
ethanamine

A

CaO
CUO
NaOH
LiOH
Ca(OH)2
Ba(OH)2
NH3
CH3CH2NH2

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8
Q

8.1 In organic acids,
which H+ atom is
lost for a proton
donor?

A

The H+ lost is the one at the end:
For example,
CH3COOH/CH3COO-
rather than
C2H402 /C2H302-

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9
Q

8.2 List some of the
common strong and
weak acids.

A

H2S04
HNO3
HCl
HI
HBr
**the “gens”

everything else (including HF) are usually weak
acids
-NH4Cl

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10
Q

8.2 Distinguish
between strong and
weak bases and
provide examples.

A

*not all bases have hydroxide ions, the ones that
do are strong bases
Bases which are not hydroxides:
-ammonia
-soluble carbonates
-hydrogen carbonates

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11
Q

8.4 A stronger acid
has a
conjugated base.
Alternatively,
(complete the
sentence)

A

A stronger acid has a weaker conjugated base
A stronger base has a weaker conjugated base

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12
Q

8.3 List out the
products of:
acid + active metal
metal oxide + acid
metal hydroxide +
acid
acids + metal
carbonates
acids + metal
hydrogen
carbonates

A

acid + active metal -> salt + H2
metal oxide + acid -> salt + water
metal hydroxide + acid -> salt + water
acids + metal carbonates -> salt + water + CO2
acids + metal hydrogen carbonates -> salt + water + CO2

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13
Q

18.1 Define an acid
and a base using
Lewis theory (and
justify whether they
like electrons or
not), and explain
what occurs when
they react together.

A

• A Lewis acid is a lone pair acceptor and a Lewis
base is a lone pair donor.
• When a Lewis base reacts with a Lewis acid a
coordinate bond is formed
• A nucleophile is a Lewis base and an
electrophile is a Lewis acid.

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14
Q

18.2 State how to
find Kw, and the
relationship
between Ka and
pKa (Kb and pKb).

A

• For a conjugate acid base pair, Ka × Kb = Kw
• The relationship between Ka and pa is (pKa
-log Ka), and between Kb and pKb is (pKb = -log
Kb)

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15
Q

18.2 State the
expression for the
dissociation
constant of a weak
acid (Ka) and a
weak base (Kb).

A

Ka=×^2/C-X
where c is the concentration and x is [H+]
Kb = x^2/C-X
where c is the concentration and x is [OH-]
**students should state when approximations are
used in equilibrium calculations.

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16
Q

8.4 Distinguish
between a strong
acid and a weak
acid.

A

• Strong and weak acids and bases differ in the
extent of ionization.
strong acid:
dissociates completely
weak acid:
partially dissociates
• Strong acids and bases of equal concentrations
have higher conductivities than weak acids and
bases.

17
Q

8.4 Describe three
tests that can be
carried out in the
laboratory, and the
expected results, to
distinguish between
0.10 moldm-3
HCI(ag) and 0.10
moldm-3
CH3COOH(ag).

A

measuring electrical conductivity and strong acids
have greater electrical conductivity/weak acids
have lower electrical conductivity;
Do not accept conductivity for electrical
conductivity.
Accept explanation in terms of lightbulb in circuit.
measure pH/use universal indicator and pH higher
for weak acid/pH lower for strong acid;
conduct titration with a strong base and
equivalence point higher for weak acid / buffer
region for weak acid;
adding a reactive metal/ carbonate/hydrogen
carbonate and stronger effervescence/faster
reaction with strong acids;
Accept converse argument.
Accept correct example.
adding a strong base and strong acid would
increase more in temperature/weak acids
increase less in temperature;
Accept correct example.
Award [l max] for three suitable tests without
correct results.
Accept specific examples with given strong acid
and weak acid.
Accept “addition of AgNO3(aq)AgNO3(aq) and
white precipitate with HCl (ag)”.
Do not accept “smell”

18
Q

8.5 Distinguish
between normal
rain and acid rain
using reaction
equations.

A

• Rain is naturally acidic because of dissolved CO2
and has a pH of 5.6. Acid deposition has a pH
below 5.6.
CO2 + H20 = H2CO3 (ag)
• Acid deposition is formed when nitrogen or
sulfur oxides dissolve in water to form HNO3
(nitric), HNO2 (nitrous), H2S04 (sulfuric acid) and
H2SO3 (sulfurous acid)
**these acids are much stronger than carbonic
acid.
Reaction with Nitrogen:
N2 + 02 -> 2NO.
can further oxidize:
2NO + 02 -> 2N02 •
4N02 + 2H20 + 02 -> 4HNO3
or
2N02 • + H20 -> HNO3 + HNO2
Reaction with sulfur oxides:
S + 02 -> S02
can further oxidize:
2SO2 + 02 -> 2503

SO2 + H20 -> H2S03
SO3 + H20 -> H2S04

19
Q

8.5 List out the
sources of oxides of
sulfur and nitrogen.

A

Nitrous monoxide:
-formed during lightning storms with the reaction
of nitrogen and oxygen in the atmosphere
-reactions that take place in internal combustion
engines
Sulfur dioxide:
-released naturally during volcanic eruptions
-released when coal and oil (which contains
Sulphur) are burned in power stations
-oxidized in combustion processes
S + 02 -> S02

20
Q

8.5 Explain the
effects on acid
deposition, using
reaction equations
(for some of them).

A

materials:
-corrosion
CaCO3 is found in marbles and limestones
CaCO3 + H2S04 -› CaSO4 + H20 + CO2
LiDL
D
plants:
-leaches important nutrients (e.g. Mg 2+. Ca 2+,
and K+) ions from the soil, making plants unable to
grow
-releases Al 3+ ions from rocks into soil, which
damages roots of plants and prevents them from
taking up water and nutrients
water:
-fish cannot survive in acidic conditions below 5
-Al 3+ (from interaction of rock and H+ ions)
interfere with operation of fish gills and reduce
their ability to take in 02
Al (OH)3 + 3H+ -> Al 3+ + H20
**Al (OH)3 is Al present in rocks
-can cause eutrophication in lakes as Nitrate ions
cause excessive plant growth -> reduce
biodiversity
human health:
-affect mucous membranes and lungs
-cause irritations
-exacerbating the symptoms of people with
respirating conditions

21
Q

8.5 Distinguish
between the pre-
combustion and
post-combustion
methods of
reducing sulfur
oxides emissions

A

combustion: removing S before coal is
combusted
e.g. hydrodesulfurisation
-S is removed from fine petroleum products
-requires a catalyst
-S removed from product in the form of H2S
post combustion: removing SO2 from exhaust
gases once they have been formed by reacting
with a base
e.g. flue gas desulfurisation
-levels of SO2 emissions in flue gas can be
reduced by passing them into a flue gas
desulfurisation tower
-or passed through sprayed aqueous suspension
of CaCO3
CaCO3 + S02 -> CaSO3 + CO2
CaO + S02 -> CaSO3
2CaSO3 + 02 -> 2CaS04
-soils and lakes with lower pH can be treated with
calcium hydroxide/limestone (neutralisation
reaction)
CaCO3 + H2S04 -> CaS04 + H20 + CO2
H2S04 + Ca(OH)2 -> CaS04 + H20

22
Q

8.5 State what is
meant by the term
acid deposition.

A

process by which acidic (substances) leave
atmosphere/return to Earth
acidic/acid-forming pollutants deposited on the
Earth’s surface/leave the atmosphere / rain/
precipitation/deposition that is acidic/ with a
pH<5.6pH<5.6;
Award mark if two specific examples are given

23
Q

18.2 Define a buffer
solution.

A

A solution that resists change in pH when small
amounts of acid or base is added

24
Q

18.2 Describe the
composition of an
acidic buffer
solution.

A

(solution containing significant/equal amounts of
a) weak acid and its salt / (solution containing)
strong base to which excess of weak acid has
been added / OWTTE;
Accept (solution containing) weak acid and
conjugate base.
Do not accept descriptions with specific
compounds alone (e.g. CH3COOH and
CH3COONa) unless compounds are stated as
weak acid and its salt
Accept answer such as (solution containing) x mol
of weak acid and 12xmol of strong base.

25
Q

18.2 Explain the
relationship
between Kw and
temperature.

A

The dissociation of water molecules into ions is
bond breaking and is therefore an endothermic
process
-increase in temp = increase in production of [H+]
AND [OH-]
-therefore leads to lower pH and pOH

26
Q

18.3 The
characteristics of
the pH curves
produced by the
different
combinations of
strong and weak
acids and bases.
Draw the pH curves
that involved the
titration of:
-strong acid with
strong base
-strong acid with
weak base
-weak acid with
strong base
-weak acid and weak base

In addition, state
their (range of)
equivalence points

A

strong acid with strong base
-pH 7
strong acid with weak base
-pH 3< eq point < pH7
weak acid with strong base
-pH 7 < eq point < pH11
weak acid with weak base
-no significance change in pH
-titration does not give clear equivalence point

27
Q

18.3 Define an acid
base indicator.

A

An acid-base indicator is a weak acid or a weak
base where the components of the conjugate
acid-base pair have different colours.
Acid indicator:
Hin= H+ + In-
HIn: color A
In: color B
-in acid, eq shift to left
-in alkali solution eq lies to right
-color change when [HIn]=[In-]
Base indicator:
BOH = B++ OH-
BOH: color A
B+: color B
**The colour change can be considered to take
place over a range of
pKa+1.

28
Q

18.3 State and
explain the
relationship
between the pH
range of an
indicator and its
pKa value.

A

color change occurs when [HIn]=[In-];
pH=pKa;
OR
pH range is a range of pH values either side of
pKa value;
lower pH when acid colour is seen and upper pH
when alkaline colour seen;

29
Q

18.3 Define a buffer
region.

A

The buffer region on the pH curve represents the
region where small additions of acid or base
result in little or no change in pH

30
Q

18.3 Explain how
buffer solution can
be made.

A

While the nature of the acid-base buffer always
remains the same, buffer solutions can be
prepared by either:
-mixing a weak acid/base with a solution of a salt
containing its conjugate
OR
-partial neutralization of a weak acid/base with a
strong acid/base.

Chemistry Ib (4 decks)

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