Suggested answers to in-text activities and exercises
New 21st Century Chemistry
Suggested answers to in-text activities and unit-end
exercises
Topic 8 Unit 33
In-text activities
Internet Search & Presentation (page 207)
The aspirin story
The history of aspirin and other medicines dealing with pain,
fever or inflammation reveals many interesting points about
scientific methodology and the interaction of people and society
with technology. One overriding theme that emerges when looking at
the development of medicines is the importance of sharing
information and cooperation in research. Time and again discoveries
in one part of the world have been published, but not developed
fully until another person reads and uses the information in
another time and place.
The textbook gives some detail of the history of the development
of aspirin, but it is intended that students find out more than
what has been given to them.
Conditions that aspirin helps to relieve or cure
At over-the-counter dosage (one or two grams), it relieves fever
and minor aches and pains. At dosages three or four times higher,
available by prescription only, it reduces swelling and is used to
treat gout, rheumatoid arthritis, and inflammatory ailments. Many
people take low dosages (below 100 milligrams) daily for preventing
recurrent stroke or heart attack. Recent studies found it effective
in reducing risks for colon and breast cancers. Evidence is
accumulating for similar effects in Alzheimer and other
diseases.
However, aspirin can irritate the stomach and in some cases
cause ulcer and internal bleeding. Alternative treatments for pain
relief are available: paracetamol and ibuprofen.
Making aspirin soluble
One problem with aspirin is that it is not particularly soluble
in cold, or even warm, water (e.g. 36 °C – the temperature of the
human body).
A medicine tablet works far better if it is water-soluble,
because it then enters the bloodstream more rapidly. One way of
making the aspirin ‘soluble’ is to convert it to one of its salts,
e.g. the sodium salt. As this product is ionic, it would be much
more water-soluble than the parent covalent acid – aspirin
itself.
Clinical trials
A new medicine has to demonstrate its safety, quality and
efficacy through a series of rigorous clinical trials in order to
obtain a licence and be available to the general public.
Clinical trials are conducted in phases. The trials at each
phase have a different purpose and help scientists answer different
questions.
•In Phase I trials, researchers test an experimental drug in a
small group of people (20 – 80) for the first time to evaluate its
safety, determine a safe dosage range, and identify side
effects.
•In Phase II trials, the experimental study drug is given to a
larger group of people (100 – 300) to see if it is effective and to
further evaluate its safety.
•In Phase III trials, the experimental study drug is given to
large groups of people (1 000 – 3 000) to confirm its
effectiveness, monitor side effects, compare it with commonly used
treatments, and collect information that will allow the
experimental drug to be used safely.
•In Phase IV trials, post marketing studies delineate additional
information including the drug’s risks, benefits, and optimal
use.
References:
http://www.creatingtechnology.org/biomed/aspirin.htm
http://docbrown.info/page04/OilProducts15.htm
http://www.abpi.org.uk//publications/briefings/clinical_brief.pdf
http://clinicaltrials.gov/ct2/info/understand
Internet Search & Presentation (page 215)
Soap-making by ancient people
Soap making is one of the oldest known organic chemical
reactions. Soaps are formed by the reaction of fats or oils with an
alkali. It is possible that the process could have been discovered
in prehistoric times when animal fat from cooking meat dripped onto
wood ash (which is alkaline) producing a crude soap. Archaeologists
once found evidence that the Babylonians were making soap around
3000 BC. Soap making was probably introduced to Europe by the
Phoenicians around 600 BC.
The Romans also produced soap. The word soap in many languages
is derived from a famous Roman legend. According to this legend
women who washed clothes in the stream below Sapo Hill noticed how
much easier they were to clean than in other streams. It seemed
that the ashes and fats from sacrificial fires in temples on Sapo
Hill mixed together to produce soap which was washed down from the
hill. A soap-making factory, complete with soap moulds and bars of
soap, was discovered in the ruins of Pompeii. With the fall of the
Roman Empire, soap making declined and soap was used mostly for
cleaning clothes and textiles rather than for personal bathing.
Commercial production of soap in Europe
Soapmakers’ guilds began to spring up in Europe during the
seventeenth century. Southern European countries, such as Italy,
Spain, and France were early production centers for soap.
The English began soapcrafting during the twelfth century.
Unfortunately, soap was heavily taxed as a luxury item, and so it
was only readily available to the rich. In 1853, when the English
soap tax was repealed, a boom in the soap trade coincided with a
change in the social attitudes toward personal cleanliness.
In America, soap was made by women producing it out of their
homes seasonally. The commercial production of soap did not start
until the early 1600s when enterprising soapmakers from England
began arriving in the New World.
Scientific advancements and soap-making
Scientific advancements that affected the soapmaking trade began
with Nicholas Leblanc, a French chemist who patented a process for
making an alkali from common salt in 1791. His process allowed for
the inexpensive production of soda ash.
In the early 1800s, Michel Chevreul's significant discoveries
about the relationship of fats, glycerine, and fatty acids laid the
groundwork for the chemistry of soaps and fats.
During the mid 1800s, Belgian chemist Ernest Solvay discovered
the ammonia process that improved the methods for extracting soda
ash from common salt. This increased the availability and quality
of soda ash for soap making.
As a result of the scientific achievements, soap became a
popular and easy-to-obtain commodity.
Production of soapless detergents
Soapless detergents use materials called surfactants which
dissolve greases; detergent effects of certain synthetic
surfactants were first noted in 1913 by A Reychler, a Belgian
chemist. During World War I the Germans used soapless detergents as
an alternative to soap but after that war their uses were largely
confined to industrial processes.
After World War II the U.S. aviation fuel plants changed over to
making tetrapropene, used in household detergents, causing a fast
growth of household use in the late 1940s. The first product was a
‘soapless shampoo’. Up to the 1960s they were more expensive than
traditional soaps but they could be used with hard or soft water
equally well.
In the late 1960s biological detergents, containing enzymes and
better suited to dissolve protein stains such as egg stains, were
introduced in the U.S..
References:
http://inventors.about.com/library/inventors/blsoap.htm
http://www.harvestsoaps.com/history_of_soap.htm
http://www.soapmakingfun.com/making-homemade-soap/history-of-soap-making.shtml
http://www.sappohill.com/soaphistory.html
http://www.worldlingo.com/ma/enwiki/en/Detergent
http://www.igg.org.uk/gansg/12-linind/soap.htm
Checkpoint (page 225)
1CH3(CH2)14CH2— is a non-polar group which can dissolve in
grease. is a polar group which can dissolve in water.
2a)Detergent I
b)
c)Before shaking an oil-water mixture, the hydrocarbon ‘tails’
of detergent particles are soluble in the oil and the anionic
‘heads’ are soluble in the water.Upon shaking, oil droplets form.
Each droplet is surrounded by detergent particles with the anionic
‘heads’ in the water.Repulsion between the anionic heads prevents
the oil droplets from coming together again. Thus, the oil droplets
remain suspended in the water. An emulsion is formed.
d)Detergent I functions well in hard water.When detergent II is
added to hard water, scum forms.A lot of the detergent is needed to
get a lather.
e)Not suitableSea water contains a lot of metal ions, such as
magnesium ions and calcium ions.Detergent II will react with the
metal ions to form scum and hence reduce the effectiveness of the
detergent.
Checkpoint (page 236)
1
2a)
b)Carboxyl group; hydroxyl group
Checkpoint (page 244)
1a)Ester functional group; carbon-carbon double bond
b)
c)X is formed from an unsaturated carboxylic acid.It is a liquid
at room temperature as its molecules cannot pack together closely
due to the presence of cis double bonds.
2a)First gently heat, while stirring, a mixture of fat and
concentrated sodium hydroxide solution for about 20 minutes. Most
of the soap formed dissolves in the reaction mixture.Then add
concentrated sodium chloride solution to the mixture. The soap
separates from the solution and floats on the surface.Obtain the
soap by filtration. Then wash the soap with a little distilled
water and allow to dry.
b)
c)Saponification
Checkpoint (page 249)
a)Amine functional group, carboxyl group, amide functional
group, ester functional group
b)
Internet Search & Presentation (page 249)
Saccharin
Saccharin was discovered over a century ago and has been used as
a non-caloric sweetener in foods and beverages for more than 100
years. Saccharin contributes no calories to the diet because it is
not metabolized by the human body. (It is excreted in the same form
as ingested.)
Uses of saccharin
Saccharin is useful for people trying to control their weight.
Saccharin may assist in weight management, control of blood glucose
and prevention of dental caries.
Saccharin is appropriate for medical and nutrition therapy for
people with diabetes, and dietetic professionals may incorporate
saccharin into the individualized meal plans of their patients who
have diabetes.
References:
http://www.saccharin.org/pdf/sach_broch_final_406.pdf
http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures---S/Saccharin.htm
Sucrose
Sucrose or table sugar is obtained from sugar cane or sugar
beets.
Sucrose is made from glucose and fructose units. The glucose and
fructose units are joined by a glycosidic linkage.
Uses of sucrose
Sucrose and its co-products lend themselves to possibilities in
many areas:
•fine chemicals;
•pharmaceuticals;
•polymers;
•building and structural materials;
•fermentation or enzyme substrate for chemicals production;
•new food products and sweeteners;
•making biodiesel / ethanol;
•transformation of cane or beet plant to make other
products.
References:
http://www.spriinc.org/buton10bftpp.html
http://www.elmhurst.edu/~chm/vchembook/546sucrose.html
Cellulose
Cellulose is a natural polymer of the β-glucose monomer. Two
b-glucose monomer molecules can link together via an oxygen atom at
the first carbon atom (C1) of one unit and the fourth carbon atom
(C4) of the next. A water molecule is released. This is a
condensation reaction. The link between the two glucose units is
called a glycosidic linkage.
Uses of cellulose
Cellulose has been used to make paper since the Chinese first
invented the process around AD 100. Cellulose is separated from
wood by a pulping process that grinds woodchips under flowing
water. The pulp that remains is then washed, bleached and poured
over a vibrating mesh. When the water finally drains from the pulp,
what remains is an interlocking web of fibres that, when dried,
pressed, and smoothed, becomes a sheet of paper.
Cellulose is the major constituent of textiles made from cotton,
linen and other plant fibres.
Cellulose can also be processed and chemically modified to make
plastics, photographic film, and rayon. Cellulose derivatives can
be used as adhesives, explosives, thickening agents in food, and
moisture-proof coatings. Historically, cellulose made some of the
first synthetic polymers like cellulose nitrate, cellulose acetate,
ethyl cellulose and rayon.
References:
http://www.scienceclarified.com/Ca-Ch/Cellulose.html
http://en.wikipedia.org/wiki/Cellulose
http://web1.caryacademy.org/chemistry/rushin/StudentProjects/CompoundWebSites/2000/Cellulose/uses.htm
Starch
The main sources of starch are the cereal crops, rice, maize,
wheat and the root crop potatoes.
Starch is composed of a mixture of two substances: amylose, an
essentially linear polysaccharide, and amylopectin, a highly
branched polysaccharide. Both forms of starch are polymers of
a-glucose. Natural starches contain 10 – 20% amylose and 80 – 90%
amylopectin.
Amylose typically consists of more than 1 000 glucose units link
together via oxygen atoms between the first carbon atom (C1) of one
unit and the fourth carbon atom (C4) of the next. The link between
glucose units is called a glycosidic linkage.
Chains of glucose units with such glycosidic linkages tend to
assume a helical arrangement.
Amylopectin has a structure similar to that of amylose, with the
exception that in amylopectin the chains are branched. Branching
takes place between C6 of one glucose unit and C1 of another and
occurs at intervals of 20 – 25 glucose units.
These two molecules are assembled together to form a
semi-crystalline starch granule. The granule also contains small
amounts of lipid and phosphate. The exact proportions of these
molecules and the size of the granule vary between species.
Examples of use of starch
Food and drinks
Animal feed
Agriculture
Plastic
Pharmacy
Building
Textile
Paper
Various
mayonnaise
pellets
seed coating
biodegradable plastic
tablets
mineral fibre
warp
corrugated board
oil drilling
baby food
by-product
fertilizer
dusting powder
gypsum board
fabrics
cardboard
water treatment
bread
concrete
yarns
paper
glue
soft drinks
meat products
confectionery
Source: International Starch Institute, Aarhus, Denmark
References:
http://www.starch.dk/
http://jxb.oxfordjournals.org/cgi/content/full/54/382/451
Cholesterol
Cholesterol is a waxy, fat-like compound that belongs to a major
class of lipids called steroids. It's found in many foods, in the
bloodstream and in all the body’s cells.
Cholesterol comes from two sources: the body and food. The liver
and other cells in the body make about 75% of blood cholesterol.
The other 25% comes from food.
Functions of cholesterol
Cholesterol is essential for
•formation and maintenance of cell membranes (helps the cell to
resist changes in temperature and protects and insulates nerve
fibres);
•formation of sex hormones;
•production of bile salts, which help to digest food;
•conversion into vitamin D in the skin when exposed to
sunlight.
‘Good’ and ‘bad’ cholesterol
Cholesterol cannot dissolve in the blood. It has to be
transported to and from the cells by carriers called lipoproteins.
Lipoproteins consist of protein, cholesterol, triglycerides and
phospholipids. The density of these lipoproteins is determined by
the amount of protein in the molecule. The terms ‘good’ and ‘bad’
cholesterol refer to high density lipoproteins (HDL) and low
density lipoproteins (LDL) respectively.
When too much LDL (bad) cholesterol circulates in the blood, it
can slowly build up in the inner walls of the arteries that feed
the heart and brain. Together with other substances, it can form
plaque, a thick, hard deposit that can narrow the arteries and make
them less flexible. This condition is known as atherosclerosis. If
a clot forms and blocks a narrowed artery, heart attack or stroke
can result.
About one-fourth to one-third of blood cholesterol is carried by
high-density lipoprotein (HDL). HDL cholesterol is known as ‘good’
cholesterol, because high levels of HDL seem to protect against
heart attack. Low levels of HDL also increase the risk of heart
disease.
Medical experts think that HDL tends to carry cholesterol away
from the arteries and back to the liver. Some experts believe that
HDL removes excess cholesterol from arterial plaque, slowing its
buildup.
References:
http://health.howstuffworks.com/cholesterol1.htm
http://www.americanheart.org/presenter.jhtml?identifier=512
http://www.scientificpsychic.com/health/lipoproteins-LDL-HDL.html
Insulin
Glucose provides energy to all of the cells in the body. The
cells take in glucose from the blood and break it down for energy.
The glucose in the blood comes from food.
When a person eats food, glucose gets absorbed from the
intestines and distributed by the bloodstream to all of the cells
in the body. The body tries to keep a constant supply of glucose
for the cells by maintaining a constant glucose concentration in
the blood. So, when there is an oversupply of glucose, the body
stores the excess in the liver and muscles by making glycogen, long
chains of glucose. When glucose is in short supply, the body
mobilizes glucose from stored glycogen and / or stimulates the
person to eat food.
To maintain a constant blood-glucose level, the body relies on
two hormones produced in the pancreas that have opposite actions:
insulin and glucagon.
Insulin consists of two polypeptide chains, an A chain and a B
chain, joined together by disulphide bonds. The smaller of the two
chains is referred to as the A chain and is 21 amino acids long in
humans. The second chain is referred to as the B chain and is 30
amino acids long in humans.
Source: http://www.chemistryexplained.com/Hy-Kr/Insulin.html
Functions of insulin
Insulin is required by almost all of the body’s cells, but its
major targets are liver cells, fat cells and muscle cells. For
these cells, insulin does the following:
•stimulates the liver and muscle cells to store glucose in
glycogen;
•stimulates the fat cells to form fats from fatty acids and
glycerol;
•stimulates the liver and muscle cells to make proteins from
amino acids;
•inhibits the liver and kidney cells from making glucose from
intermediate compounds of metabolic pathways (gluconeogenesis).
Diabetes
Diabetes is classified into three types: Type 1, Type 2 and
gestational diabetes.
Type 1 is caused by a lack of insulin. This type is found in 5 –
10% of diabetics and usually occurs in children or adolescents.
Type 2 occurs when the body does not respond or cannot use its
own insulin. Type 2 occurs in 90 – 95% of diabetics and usually
occurs in adults over the age of 40, most often between the ages of
50 and 60.
Gestational diabetes can occur in some pregnant women and is
similar to Type 2 diabetes. During pregnancy, several hormones
partially block the actions of insulin, thereby making the woman
less sensitive to her own insulin.
References:
http://health.howstuffworks.com/diabetes1.htm
http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/insulin_struct.html
http://www.providence.edu/chm/kcornely/Case%204_%20The%20structure%20of%20insulin.pdf
Casein
Milk is a complex biological fluid with high amount of proteins,
lipid and minerals. The function of milk is to supply nutrients
such as essential amino acids required for the growth of the
newborn.
Originally, milk proteins were believed to be a simple
homogeneous protein, but about a century or more ago, milk proteins
were divided into two broad classes. The first fraction, which is
about 80% of the protein in bovine milk, is called casein. The
second fraction, which makes up about 20% of protein, is referred
to as whey protein, serum protein or non-casein nitrogen.
Casein exists in milk in complex groups of molecules that are
called ‘micelles’.
A typical micelle contains on the order of 104 polypeptide
chains of four basic types, together with about 3 x 103
microgranules of an amorphous calcium phosphate. The micelles are
polydisperse in size and variable in composition.
Due to the importance of casein and casein micelles for the
functional behaviour of dairy products, the nature and structure of
casein micelles have been studied extensively, but the exact
structure of casein micelles is still under debate.
Various models for casein micelle structure have been proposed.
Most of the proposed models fall into three general categories:
coat-core, subunit (sub-micelles), and internal structure
models.
Functions of casein
The casein micelle is an important and characteristic
macromolecular assembly of mammalian biology, occurring in all
milks that have been examined in sufficient detail. Its functions,
insofar as they are known, are to form a coagulum in the stomach of
the nursling, allowing the slow release of nutrients down the
digestive tract, and to act as a means of transporting calcium and
phosphate in a readily assimilable form from mother to young. As
well as providing a source of amino acids, enzymatic cleavage of
casein polypeptide chains can produce various types of biologically
active peptides.
Another recent speculation is that casein has a role in
protecting the mammary gland against ectopic calcification, a
hazard that is common to all tissue in contact with supersaturated
calcium solutions.
References:
http://www.nzic.org.nz/ChemProcesses/dairy/3E.pdf
http://books.google.com.hk/books?id=9H_gemXpEWQC&pg=PA63&lpg=PA63&dq=structure+of+CASEIN&source=bl&ots=mxmH460AUp&sig=M-EfF2UOtYlYE9E6L-MUH3YTQzw&hl=zh-TW&ei=KaL8S_T7N4uTkAWGi9iMBw&sa=X&oi=book_result&ct=result&resnum=10&ved=0CDcQ6AEwCTge#v=onepage&q=structure%20of%20CASEIN&f=true
http://rdo.psu.ac.th/sjst/journal/27-1-pdf/19casein-micelle.pdf
Unit-end exercises (pages 255 – 267)
Answers for the HKCEE (Paper 1) and HKALE questions are not
provided.
1a)i)B
ii)A
b)
2When we add a detergent solution to a table cloth stained with
grease, the hydrocarbon ‘tails’ of the detergent particles dissolve
in the grease. The anionic ‘heads’ of the detergent particles are
insoluble in the grease and remain outside.The surrounding water
molecules attract the anionic ‘heads’ and lift the grease off the
surface.By stirring, the grease (which carries the dirt particles)
breaks up into tiny droplets suspended in the water. These tiny
droplets cannot come together again due to the repulsion between
the anionic ‘heads’ of detergent particles on their surfaces. An
emulsion forms.Rinsing washes away the greasy suspension, and
leaves the surface clean.
3a)Ahexane-1,6-dioic acid
Bhexane-1,6-diamine
b)Condensation polymerization
c)
4a)
b)i)
ii)Condensation polymerization
c)Fibres used to make clothesBottles for carbonated drinks
d)By the hydrolysis of the ester linkage by enzymes or
microorganisms
5Carbonyl groupHydroxyl group
6B
7B
8B
9B
10B(1)X is a condensation polymer.
(2)X is formed from the condensation polymerization of two
different monomers.
11—
12—
13—
14a)Little / no latherScum
b)Add dilute nitric acid followed by silver nitrate solution.A
white precipitate forms.
c)There are several ions that would give a colour flame.
15a)Ester functional group; carbon-carbon double bond
b)i)Saponification
ii)First gently heat, while stirring, a mixture of vegetable oil
and concentrated sodium hydroxide solution for about 20 minutes.
Most of the soap formed dissolves in the reaction mixture.Then add
concentrated sodium chloride solution to the mixture. The soap
separates from the solution and floats on the surface.Obtain the
soap by filtration. Then wash the soap with a little distilled
water and allow to dry.
c)Hydrogenation of vegetable oils
d)Hydrocarbons from petroleum, concentrated sulphuric acid and
sodium hydroxide
e)Bacteria use up oxygen in the water during the decomposition
of detergents. This makes the water of some streams, rivers and
seas smell badly due to oxygen depletion.
16a)
b)When the soap is added to hard water, scum forms.The scum
forms because the calcium and magnesium ions in hard water react
with the soap, giving an insoluble product that floats on the
water.
c)Washing soda reacts with calcium ions and magnesium ions in
hard water to form insoluble carbonates, thus removing the hardness
of water.
17a)i)Carbon and hydrogen
ii)
iii)Permanent dipole-permanent dipole attractions
iv)Reflux glycerol and carboxylic acid in the presence of
concentrated sulphuric acid.
b)i)Hydrogen bonding is the attraction between the hydrogen atom
attached to an oxygen atom and the lone pair on another oxygen
atom.
ii)Glycerol is soluble in water because its molecules can form
many hydrogen bonds with water molecules.The boiling point of a
compound depends on the strength of its intermolecular
attractions.Strong hydrogen bonds exist in glycerol.Hence a lot of
heat is needed to separate the glycerol molecules during
boiling.Thus glycerol has a relatively high boiling point.
c)i)Propene
ii)Petroleum
iii)Substitution
iv)Sodium hydroxide solution
v)
vi)Number of moles of compound A =
= 0.71 mol
Theoretical yield of glycerol = 0.71 mol x 92.0 g mol–1
= 65 g
Percentage yield of glycerol = x 100%
= 3%
18a)Monomer molecules join together repeatedly to form polymer
molecules.Small water molecules are formed during the reaction.
b)
c)
19a)
b)i)
(any one of the hydrogen bonds is acceptable)
ii)Strong hydrogen bonds hold the polymer chains and water
molecules together.
c)i)Permanent dipole-permanent dipole attractions exist between
chains of the polymer derived from compound A while hydrogen bonds
exist between chains of the polymer derived from compound B.Hence
chains of the polymer derived from compound A can slide past one
another more easily.Thus the polymer is more flexible.
ii)
iii)NoThe polymer does not contain carbon-carbon double
bond.
20a)Any one of the following:
•To improve the quality.
•To reduce cost.
•The demand is greater than the nature can supply.
b)
c)i)butane-1,4-diamine
ii)Any two of the following:
•Lower melting point
•Lower strength
•Lower rigidity
d)i)Number of repeating units =
= 151
ii)Amide functional group
iii)The number of hydrogen bonds per unit length of polymer
chain of Stanyl is greater than that of nylon-6,6.Hence more heat
is needed to overcome the forces between the polymer chains of
Stanyl, enabling the chains to move over one another.
e)i)
ii)
(any one of the hydrogen bonds is acceptable)
21a)Number of moles of CO2 produced by 0.10 g of Z =
= 2.2 x 10–3 mol
Mass of C in 0.10 g of Z = 2.2 x 10–3 mol x 12.0 g mol–1
= 0.026 g
Mass of H in 0.10 g of Z = 0.020 g x
= 2.2 x 10–3 g
Mass of O in 0.10 g of Z = (0.10 – 0.026 – 2.2 x 10–3) g
= 0.072 g
( the empirical formula of Z is CHO2.
b)Let (CHO2)n be the molecular formula of Z.Molar mass of Z=
n(12.0 + 1.0 + 2 x 16.0) g mol–1
= 90.0 g mol–1
n= 2
∴ the molecular formula of Z is C2H2O4.
c)Number of moles of 0.900 g of Z =
= 0.0100 mol
Number of moles of NaOH required for complete neutralization
= 1.00 mol dm–3 x dm3
= 0.0200 mol
0.0100 mole of Z requires 0.0200 mole of NaOH for complete
neutralization.
i.e. 1 mole of Z requires 2 moles of NaOH for complete
neutralization.
It can be deduced that Z should contain two –COOH groups.
(the structural formula of Z is .
d)WCH2=CH2
XBrCH2CH2Br
YHOCH2CH2OH
e)C20H42 ( C18H38 + C2H4
22
23—
24—
25—
20.0
1 000
0.900 g
90.0 g mol–1
2.0 g mol–1
18.0 g mol–1
53 cm3
24 000 cm3 mol–1
3 x 104
198.0
2 g
65 g
30 g
42 g mol–1
Suggested answers to in-text activities and unit-end exercises
21© Jing Kung. All rights reserved.
Topic 8 Unit 33