The Acidic Environment Flashcards
1
Q
what are some properties of acids?
A
- they taste sour
- they can conduct electricity
- strong concentrations will give a burning feeling during contact
2
Q
what are some common acids?
A
vinegar(acetic acid) lemon juice(citric acid) Battery Acid(sulfuric acid) vitamin c(ascorbic acid) Nitric Acid(HNO3) Hydrochloric Acid (HCl) Carbonic acid(H2CO3)
3
Q
what are some properties of bases?
A
- they are often bitter tasting and slippery to touch
- can conduct electricity
- strong concentrations will often give a burning sensation if it comes into contact with skin
4
Q
what are some common bases?
A
Ammonia baking soda detergent toothpaste soap sodium hydroxide potassium hydroxide slaked lime magnesium hydroxide
ANYTHING WITH A HYDROXIDE
5
Q
what are some common neutral substances?
A
water
salt water
ethanol
glucose solution
6
Q
what is an indicator?
A
an indicator is a subtance which, in solution, changes colour depending on the pH of a substance
7
Q
what is the disadvantage of using indicators?
A
indicators do not give quanitative measure of a subtances pH. it will only provide a loose guide as to how acidic or basic something is, damaging accuracy.
8
Q
what is universal indicator made of ?
A
universal indicator is a mixture of many different indicators. it provides a range of colours over the acid-alkali range rather than the usual two colours with single indicators
9
Q
what are the indicators i need to know in the hsc course?
A
litmus phenolphthalein methyl orange methyl red bromothymol blue
10
Q
from very acidic to very basic, what colour changes occur in litmus?
A
red red reddish-blue blue blue
11
Q
from very acidic to very basic, what colour changes occur in phenolphthalein?
A
colourless colourless colourless pink crimson
12
Q
from very acidic to very basic, what colour changes occur in methyl orange?
A
red yellow yellow yellow yellow
13
Q
from very acidic to very basic, what colour changes occur in methyl red?
A
red pink yellow yellow yellow
14
Q
from very acidic to very basic, what colour changes occur in bromothymol blue?
A
yellow yellow blue blue blue
15
Q
what are some uses of indicators in everyday life?
A
- testing pH of the soil
- in Fish tanks
- swimming pools
- testing domestic waste
- monitoring wastes from labs
16
Q
describe why testing pH of the soil is important
A
differing plants, fruits, vegetables, flowers etc require different levels of pH to survive and grow
17
Q
describe why testing pH in fish tanks is important
A
different fish survive in different pH levels, if this is not provided the fish will die. this range of pH is quite narrow however
18
Q
describe why testing pH in swimming pools is important
A
swimming pools must be maintained and monitored at a pH that is slightly above 7 for safety reasons. no one wants to swim in acid or base
19
Q
describe why testing pH in domestic waste water and in waste from laboratories is important
A
discharges to the sewerage system must be nearly neutral, helping to maintain a healthy environment
20
Q
whats special about non metal oxides, exclusing the neautral oxides (CO, NO, N2O)?
A
they are acidic in solution, or act acidic when reacting with bases
21
Q
what are the trends in regards to the position of metal/non metal oxides on the periodic table?
A
- metal oxides on the left hand side of the periodic table are generally basic
- non metal oxides on the right hand side of the periodic table are generally acidic
- semi metals can be amphoteric (acidic and basic properties) depending on their oxidation states
- bascity decreases down a group
- acidity increases up a group
- noble gases do not form oxides
22
Q
what is a reversible reaction?
A
a reversible reaction is a reaction which can proceed in forward and backward directions.
23
Q
when is a reversible reaction in a state of equilibrium?
A
when the forward rxn and backward rxns are occuring at the same rate.
24
Q
what are the characteristics of a system which is in equilibrium?
A
- neither forward or backward rxn will go to completion, there will always be some product and reactant
- the concentration of products and reactans are always constant
- no matter or energy leaves the system( described as closed)
- macroscopic properties (colour,smell, pressure, temperature, state) remain constant as concentrations remain constant
- microscopic changes do occur
25
what is the definition of Le Chatelier's Principle?
if a system in equilibrium is disturbed, then the system will adjust itself in order to minimise the disturbance
26
what is one thing that is important to remember about disturbances to an equilibrium?
the effects of the disturbance are never fully removed. they are only minimised, or lessened to a degree
27
what is the effect of temperature on a system in equilibrium?
-an increase in temperature will cause the system to shift in the direction that will decrease the temp of the system
for example, if the forward reaction of a reaction is exothermic, then, in response to an increase in temp, the equilibrium will shift in the backward direction to the endothermic rxn in order to decrease temperature.
THE CONVERSE OF THIS IS TRUE
28
what is the effect of pressure on a system in equilibrium and what is there to remember about changes in pressure?
in a rxn of gases, an increase in pressure of the system will result in a shift in the direction that results in the least number of moles of gas. for example, if a reaction involves 2 moles of reactant gas and 3 moles of product gas, the system will shift to favour the reactants in order to decrease the total amount of gaseous molecules. if temp is increased were there is an equal amount of moles of reactant and product, increasing or decreasing pressure does nothing
REMEMBER, CHANGES IN PRESSURE ONLY AFFECT GASES
CONVERSE IS TRUE
29
what is the effect of volume on a system in equilibrium?
affects of volume are like affects of pressure, where increasing volume is the same as decreasing pressure and decreasing volume is the same as increasing pressure.
30
what is the effect of differing concentrations of substances in a system which is in equilibrium?
consider the reaction of A + B -> C + D
- if more A or B is added, causes a shift to the right to convert excess A and B into C and D
- conversely, if more C or B is added, causes a shift to the left to convert excess C and D into A and B
31
what are the significant acidic oxides in the atomsphere?
nitrogen dioxide
nitrogen monoxide
nitrous oxide
sulfur dioxide
32
what are the industrial sources of sulfur dioxide?
- combustion of fossil fuels
- extraction and refinement of metals from sulfire ores, where sulfur dioxide is often released during the smelting of the ores in order to remove sulfur impurities from the metal
33
what are the natural sources of sulfur dioxide?
- two thirds of all sulfur dioxide are produced naturally by geothermal hot springs and volcanoes
- may arise from dihydrogen sulfide producing bacteria
34
what are the industrial sources of nitrogen monoxide/dioxide?
-combustion within power stations and motor vehices. high temperatures allow the conversion of oxygen and nitrogen into nitrogen monoxide, which combines with oxygen to form nitrogen monoxide
35
what are the natural sources of nitrogen monoxide/dioxide?
- nitrogen monoxide is produced by lightining , as the high localised temps created by lightning are enough to cause oxygen and nitrogen to from nitrogen monoxide
- nitrogen monoxide then reacts slowly to from nitrogen dioxide
36
what are the natural sources of nitrous oxide?
-formed by soil bacteria
37
what are the industrial sources of nitrous oxide?
- formed by catalytic converters in vehicles
- formed from the production of nylon
- formed from the combustion of fossil fuels
38
describe the evidence which suggests sulfur and nitrogen dioxide levels have increased?
well, because these oxides are soluble in water, there hasnt been a drastic increase of these gases on a global scale. this is because the water cycle effectively cleans the atmosphere of these oxides on a regular basis
however, trapped air bubbles in the arctic ice have shown and increase in the concentration of these gases when compared to the current composition of the atmosphere today. however, because these concnentrations are so small, they are hard to measure accurately and therefore may not be considered valid
39
describe the evidence which talks about the increase of nitrous oxides over the decades
despite the relatively stable sulfur and nitrogen dioxide levels, nitrous oxide levels in australia have increased drastically by over 130% beginning from the 1990's, with most of this being attributed to the use of fertilisers
40
what is the evidence that suggests there has been an increase in CO2 levels over the past two centuries?
- the current figure of CO2 is 360ppm, and it is rising
- this concentration is much larger than nitrogen and sulfur dioxide and so its easier to measure accurately
- carbonates are also insoluble in water unlike sulfates and nitrates. this allows past concentrations levels to be observed, while sulfates and nutrates are chemically changed and thus cannot be used for comparison
41
what conclusion can be made about the evidence surrounding acidic oxide increases?
any measurements obtained lack any real figures to compare with, as accurate methods of measurement have only been developed within the last few decades
42
whats the formulas for moles and concentration?
n=m/mr
c=n/v
C1V1=C2V2
43
how is acid rain formed ?
acid rain is formed when high enough concentrations of acidic oxides such as sulfur and nitrogen dioxide which are soluble dissolve in water and lower its pH
44
what are the effects of acid rain on the environment and infrastructure?
- increases the acidity of lakes to the point for marine life can no longer inhabit waters for extended periods of time. leads to death of fish eggs and other intolerant marine life
- forests on an international scale have been ravaged by acid rain, ravaging foliage which are neccessary parts of a plant used in photosynthesis
- acidic soils increase the solubility of aluminium ions which are toxic to life when absorbed. this inteferes with the plants normal mineral uptake
- acidic conditions for plants may stunt their growth by drawing out important mineral ions such as magneisium and calcium ions
- nitrogen fixing bacteria are negatively affected by changes in soil pH, and are vitalfor healthy plant function
- leads to the corrosion and decay of structures made from limestone and marble as they cannot calcium carbonates
also causes damage to structures made from iron as iron reacts
45
what are the health and environmental issues associated with the release of sulfur dioxide in the atmosphere?
- aggravates existing lung conditions, and can trigger ashma attacks and bronchitis
- also forms acidic rain which has its own negative effects
46
what are the health and environmental issues associated with the release of nitrogen dioxide into the atmosphere?
- can irritate airways and be detrimental for ashmatics
- in moderate levels, long-term eposure can increase the chances of respiratory illness and sentise people with allergies
- forms an even stronger acid as compared sulfur dioxide
- FORMS PHOTOCHEMICAL SMOG which is produced as a result of sunlights action on pullutants in the atmosphere creating ozone
ozone readily oxidises bodily tissue, and it highly toxic even in low concentrations
47
what are the health and environmental concerns associated with the release of nitrous oxide into the atmosphere?
-has been estimated to have a global warming potential 300x higher than CO2
48
so, considering the issues related to the release of acidic oxides into the atmosphere, what can be said for sure?
the evidence is both plentiful and persuasive, making it abundantly clear that concerns regarding the release of sulfure dioxide and the oxides of nitrogen are in fact well founded
49
WHAT ARE ACIDS?
proton donors
50
WHAT ARE BASES?
proton acceptors
51
describe the ionisation of an acid in water?
when an acid dissolves in water, the acid molecule disaccociates into its invididual ions, a hydrogen cation and an anion.
the hydrogen ion formed reacts with water to form the cation called the hydronium ion
52
what are names given to acids in respect to how many protons they donate?
monoprotic- one proton
diprotic-two protons
triprotic-three protons
53
essentially, what is the hydrogen ion?
a proton
54
what is the systematic name of acetic acid?
ethanoic acid
55
what is the formula for acetic acid?
CH3COOH
56
how is acetic acid formed naturally?
formed in bacteria as ethanol is oxidised
57
why is acetic acid formed on an industrial level?
for the production of items such as soft drink bottles, glue and vinegar
is also used as a food additive
58
what is the systematic name for citric acid?
2-hydroxypropane-1,2,3-tricarboxylic acid
59
what is the formula for citric acid?
C6H8O7
60
where is citric acid formed naturally?
widespread in animal and plant tissue, espcially in citrus fruits
normal component of blood serum and urine
61
how is citric acid formed industrially?
fermenting crude sugar with the aspergillus fungus
62
how is citric acid used?
often added to jams to give it a sharp taste as it is an antioxidant
also added to canned food to stop microbial growth
also used in textile and pharmecutical industries
63
where is HCl found naturally?
produced in the glands of the stomach to assist food digestion
64
how is HCl formed industrially?
by dissolving chlorine gas in water
65
what are the uses of HCl?
used to clean brick work
| used in the production of polyvinylchloride
66
where is sulfuric acid used?
acid used in car batteries
used as a catalyst in the dehydration and hydration of ethanol
used to manufacture explosives and fertilisers
67
what is a strong acid?
a strong acid is one that will completely ionise in water forming anions and hydrogonium ions
an example of a strong acid is HCl
68
what is a weak acid?
a weak acid is one that will partially ionise in water to form hydronium ions and anions
69
when is an acid described as concentrated?
An acid which is concentrated has a total concentration of solute, acid molecules, which is high
70
when is an acid described as dilute?
an acid which is dilute has a total concentration of solute, acid molecules, which is low
71
how do we find the pH of a solution?
-log[hydronium ion conc] to the base 10
72
an increase in pH of one means...
a ten fold decrease in hydronium ion conc
73
a descrease in pH of one means..
a ten fold increase in hydrogenium ion conc
74
how do we find the pH of a basic solusion?
14-(-log[hydroxide conc])
75
what is a buffer?
a substance that will work to maintain the pH of a system even if small amounts of acid of base are added
76
what is an example of a buffer used in a natural system?
the biocarbonate ion found in human blood
77
what are the three uses as acids as food additives?
preservatives
antioxidants
flavouring
78
why are acids used as presevatives?
acids such as acetic acid prevent microbial growth such as salmonella in foods, thus preseving food so it has a longer shelf life and minimising the risk of law suits caused by food poisoning
79
why are acids used as antioxidants?
some acids such as ascorbic acid are used as antioxidants, preventing spoilage of food due to oxygen
80
why are acids used as flavouring?
some acids such as citric acid add taste and tartness in the case of citric acid, often used in spreads(jams)
81
what combinations of acids and bases form a neautral salt?
a strong acid and a strong base or
| a weak acid and weak base
82
what combinations of acids and bases form a basic salt
weak acid and a strong base
83
what combinations of acids and bases form a acidic salt?
a weak base and a strong acid
84
what theory did lavoiser propose about acids?
he asserted that acids were compounds which contained oxygen
this theory aimed to define them based on their chemical composition
85
what were the issues associated with lavoisers theory of acids?
- the theory could not explain why some substances that did not contain oxygen displayed acidic properties, such as HCl
- couldnt explain why metallic oxides where basic, such as sodium hydroxide
86
what theory did davy propose about acids?
he proposed that all acids contain a replaceable hydrogen
reasoned that the present of hydrogen in acids gave them their acidic properties
87
how did davy reach his conclusion about his theory regarding acids?
- performed an electrolysis of HCl and found that hydrogen gas would form
- hydrogen could be replaced by a metal to form a salt
88
what was good about davy's theory of acids?
this definition aided in the development of acids definitions by relating their nature to their reactions with other substances
89
what were the issues with davy's theory of acids?
failed to explain why some substances containing hydrogen were not acidic, such as methane
did not make any connections with bases
failed to take into account acidic metals such as silver, or acidic oxides such as sulfur dioxide and nitrogen dioxide
90
what was arrhenius' theory regarding acids and bases?
proposed that acids were substances that ionised in solution to form hydrogen ions, and that bases were substances which ionised in water to form hydroxide ions.
acids ionsied in water to form ions
arrhenius also recognised that some acids were stronger than others, conversely for bases
also proposed that it is the hydrogen ion and hydroxide ion which combine together to form water in a neautralisation rxn
91
how did arrhenius come to his conclusion regarding acids and bases
-established his conclusion regarding hydrogen ions by electrolysising various acids, incluiding HCl
reasoned that the evolution of hydrogen gas was the result of hydrogen ions in soln turning into hydrogen molecules
92
what were the issues regarding arrhenius' theory of acids and bases?
- failed to explain why some salts were acidic, basic and neautral
- failed to explain why metal oxides and carbonates were basic even though they didnt produce hydroxide ions
- his explaination only applied to acqueous solutions
- it could not explain amphoteric oxides, which can behave as both acids and bases
- did not explain that the ionisation of an acid is a rxn between the acid molecule and the solvent. eg HCl in water is strong, while HCl in diethyl ether is fairly weak
93
what are alkanols?
a homolgous series of carbon compounds containing the hydroxyl group, -OH
94
what is the general formula for an alkanol?
R-OH
95
what are some features of alkanols?
- polar due to OH group
- hydrogen bonding can occur between OH groups
- soluble in water but solubility decreases with increasing chain length
- higher MPs and BPs than corresponding alkanes and alkenes
- react with alkanoic acids to form esters
96
what are alkanoic acids?
homologous series of carbon compounds containing the carboxyl group, -COOH
97
what is the general formula for alkanoic acids?
R-COOH
98
what are some features of alkanoic acids?
- polar due to carboxyl group
- strong hydrogen bonds form between neighbouring alkanoic molecules
- water soluble but solubility decreases with increasing chain length
- higher MPs and BPs than corresponding alkanes, alkenes and alkanoic acids
- they are weak acids as they partially dissolve in water
- react with alkanols to form esters
99
what is the general nomenclature for esters?
alkyl alkanoate
100
the alkyl part comes from the...
alkanol that reacts to form the ester
101
the alkanoate part comes from the...
alkanoic acid that reacts to form the ester
102
what is esterification?
the condensation reaction between an acid and alkanol through which can acid is formed.
103
is esterification reversible or nah?
its reversible
104
why is esterification a condensation reaction?
it produces water along with the ester
105
whats bad about esterification?
its an equilibrium reaction that occurs relatively slowly at room temps
106
in general, why are acids used in esterification?
- to increase the yield of ester
| - to increase the speed of the rxn by lowering the activation energy
107
why does using an acid in esterification like sulfuric acid increase the yield of ester?
concentrated sulfuric acid is a strong acid and a strong dehydrating agent, thus it actively absorbs the water in the reaction.
via Le Chateliers principle, the equilibrium will shift to the right to get back the water that is being lost and hence increasing the amount of ester in the process
108
why does using an acid in esterification like sulfuric acid lower the activation energy of the reaction?
a strong acid like sulfuric acid may donate a proton to the unshared oxygen electron pairs of either the acid or the alkanol. this, in turn, makes the alkanol and alkanoic acid more reactive. hence, this speeds up the reaction by allowing it to proceed at lower activation energies due to this increased reactivity between the reactants
109
what is refluxing?
the heating of the reactants in flask, from which vapours rise through a cooling condenser. this causes the reactants to condense and fall back into the flask, preventing them from escaping.
110
why is refluxing necessary?
according to the collision theory, more heat leads to more collisions between molecules, leading to a faster rate of reaction. this is why heating is necessary to cause the reaction to proceed to any appreciable extent. however, higher temp would also lead to faster evaporation, meaning unnacceptable amounts of reactants would be lost to the environment
refluxing keeps reactants constrained to the flask, where they can continue to react. this means higher temps and thus faster rxns can be achieved in a viable manner
in addition, refluxing also provides safety since the vapours from esterification are flammable
111
where can esters be found naturally?
in fruits, animal fats and plant oils are natural esters
112
where can esters be found artifically?
found artifically in flavourings and fragrances such as perfumes and colognes
113
what are some uses of esters and provide examples
food: scents and flavours are used such as peach (ethyl butanoate), orange( octyl ethanoate), and apple (methyl butanoate)
solvents: to dissolve both polar and non polar substances such as ethly ethanoate, used in manufacturing cellulose lacquers
flavours and scents in cosmetics: flavoured lip gloss (butyl ethanoate), creams and lotions for sore muscles (methyl solicylate), perfumes (pently ethanoate)
114
how can i make a buffer?
either equal concentrations:
- add a weak acid and its conjugate base, or a salt of that weak acid
- add a weak base and its conjugate acid, or a salt of that weak base
115
why is a buffer good in blood?
this strictly suitable because many biochemical reactions that occur in blood are only efficient at a pH around this level, enzymes denaturing is bad
116
what are the three equilibria that exists in the blood that acts as a buffer?
carbon dioxide dissolving in water to form carbonic acid
then carbonic acid reacts with water to form the hydronium ion plus hydrogen carbonate
then, hydrogen carbonate reacts with ater to form carbonic acid plus hydroxide ion
117
what is an amphiprotic substance?
a substance that can behave as both a proton donor and a proton acceptor
118
how do amphiprotic substances work?
if the substance its reacting with is a stronger proton donor, it will act as a base and vice versa
119
what are some common amphiprotic substances?
```
water
HS-
HCO3-
HPO4-
HSO4-
```
notice how all these substances have a hydrogen to donate :)
120
what is a neutralisation reaction?
a proton transfer reaction involving acids and bases
121
is a neutralisation reaction exothermic and what does this amount of heat depend upon?
yes and the amount of heat liberated depends on the strengths and concentrations of the acids and bases in question.
122
do neutralisation reactions always produce water?
no! they only involve a transfer of a proton
123
what is a titration?
experimental procedure used to dtermine the concentration of an unknown base or acid. often called volumetric analysis
124
how do titrations occur?
it works by taking the unknown sample, and then neutralising it using a measured quantity of a substance of known concentraiton. the neutralisation is detected by using an indicator that changes colour at the midpoint of the titrations, known as the equivalence point
125
which equation is used in a titration?
C1 x V1 = C2 x V2
126
what is a primary standard solution?
a solution of known concentration which is impecably accurate used to find out the concentration of an unknown solution during titration.
127
what do substances have to be in order to make them a primary standard solution?
- sufficiently high purity
- sufficiently high stability
- known formula
- solid form
- high molecular weight
- readily soluble in water
and they cant absorb moisture from the air or react with anything in the air
128
what are some examples of sustances that are used to make primary standards?
- oxalic acid
- sodium carbonate
- sodium hydrogen carbonate
129
what are the steps in setting up a primary standard solution?
1. accurately weigh out a known amount of the primary standard using a clean, 50ml beaker
2. clean your 250ml volumetric flask with distilled water and dry
3. use a wash bottle to add distilled water to the beaker of crystals and use a short glass rod to dissolve by stirring carefully
4. with a clean, small funnel, quantitavely transfer the primary standard into the volumetric flask with the aid of a glass rod and wash bottle. thoroughly irrigate the beaker and glass rod to ensure all washings and crystals are transferred into the volumetric flask
5. fill up the volumetric flask carefully with distilled water from the washbottle up to the graduation mark, with the bottom of the meniscus touching the mark
6. stopper the flask and invert the flask three times to ensure thorough mixing
130
what are the equipment for a titration?
- pipette
- burette
- white tile
- glass funnel
- distilled water and washbottle
- suitable indicator that changes colour at equivalence point
- conical flask
- base and acid
131
whats the equivalence point of a titration?
the point at which the rxn has just been completed via just the right amount of the combination of acid and base
132
what do you have to do when using the burette to improve accuracy?
- ensure no air bottles are in the burete upon filling, especially near the top of the base
- use a white tile and view the meniscus at eye level to minimise parallax errors when viewing values
- near the endpoint, the top of the burette should be turned just the right amount as to only allow drops to be dispensed into the flask
133
what do you have to do when using the pipette to improve accuracy?
- hold the pipette vertically and view the meniscus at eye level to reduce the parallax errors
- never blow at the last drop of the soln, the pipette is designed to have one final drop remaining
- when removing excess drops, touch the tip of the pipette to the bottom of the conical flask
134
what do you have to do with all glassware in a titration!!!!????
- rinse 3x with distilled water and dry thoroughly
- both the burette and pipette should be rinsed with their corresponding solns to wash out any excess water that will dilute and hence impede on the vaildity of the titration
- fill the pipette/burette with soln above the 0 mark, and controllably dispense excess soln to achieve hopefully a highly accurate volume
