1989-03-23 — Page 19

商教日六十月二年巳己腦夏

1.5Hydrolysis of Esters

CH2OH

(a)Esters are hydrolysed in the

presence of a minend' acid.ver an alkali.

CHON

1989 中學會考預習專欄

明德出版社:

CHOH

Ester, Water:

Alkanal Alkahoic acid

e.g.CH,COCH, + HD -

MILL & DALE PRESS

Chemistry (26)

Unit 15: Revision Notes on

Soaps and Detergents

1. Esters

R. Chu Esters,

1.1 General formula: RC-OR' where R and

Rore alkyl groups,

1.2Ester formation (Esterification)

Alkandic 4. Alkanol.

acid.

Cone Has

+ Water

ànd

CHCH CH, COOH:

(b)Acid hydrolysis of esters is just the reverse of esterification, The reaction is reversible. (c)Alkaline

hydrolysis

(saponification) of esters is: irreversible and the reaction is almost complete.

∙CH2O4 + C#,000TMMa

1.6Fat and oils are esters four. naturally. They are esters: formed between propan-1,2,3-trial (or alycerol) and large organic acids.. They can be represented by the Structure below.

where

lky groups

▲ represcrits

e.g+C/H,CCOH + CHOH CH COECH_HD.

1.3Physical properties of Esters

(a)ost of them are colourless. volatile, liquids: with b.p.s much lower than the alkanols and alkanoic acids. of -similar relative molecular mass. (b)They have characteristic pleasant.

frint smelis."

f:)insoluble

water but good solvents. far плачу organic

1.4Uses of Ester's

{a}as solvents for many paints and adhesives due to their volatility and good dissolving power. e.g.Ethylethanoate

: varnish remover;

(b)As artificial : flavourings Cir perfumes, food, " cosmetics: aric drinks etc.

characteristic friuty smells.

e.g.Pentyl ethanoate (pear

flavour) in sweets:.

Butyl

butanoste. (pineapple

flavour) in milk shakes:

Methyl benzoate

CH OC-

嗎

Where R and R are hydrocarbon chains saturated on.. unsaturated,

·similar or different;

2. A detergent is a substance which

cleans.

3. Soap-anatural detergent.

3.1Soaps are in fact the sodium cr potassium salts. cf/large alkaroic acids.

e.g.the most common soap is sodium octadecanuate, C7H35COO Na.

the alkaline: hydrolysis of the animal fatsor. oils, e.g. glycerine: vegetable ester. This react is ofter knownz

as saponification

flavour):

in minty

to.

their

312Soaps are made by

Trint

chewing

CH2OC

1989 中學會考預習專欄

明德出版社,

MILL & DALF PRESS

Economics (26)

TAXATION

Alain Li

Taxation: is

main

source

of

"government revenue.

Kinds of tax

Taxes can be classified according to 2 main. criteria:

A. According to income taken

According to the percentage of income taken from taxpayers, taxes Car

e classified

into

following 3 kinds:

1. Progressive tax. (選手

the

A progressive tax is one where.

Neol Q KOH

ark

noate

Soap)

3N20K

the tox race, rises as a person's income rises.

OH

Proportional tax (6 (8) A

Propertional taxis a uniform rate for all tax payerį, spective of their income

9. According t

ve tax is one, where

ate decreases as a income rises.

According taxation, taxes, ca into the following

報日僑華

detted surface

四期星:日三廿月三(九八九-)年八十七國民華中

High surface tonsion dun tG Marge Intermolecular forcas

dissolved calcium ions. (Ca2+) and/or

nagnessivations (Mg2+)..

6.2Soft water is one which does not

have any dissolved Ca2+.

Scum 15

6.3Soaps form scum (an insoluble grey

solid) in hard water. actually the magnessian and calcium ...'ss'ts of large alkanoic acids.

間新港本日六十版

Na

Soap

water.

moluculo.

Propane-1,2,3-triol {glycerol)

3.3Cleaning Action of Soap..

(a)Soap particles have a structure;

as shown below.

tonic 'hand' Hydrocarben tratat (Non-polar, hydrophoble, (Polar, hydrophilic solubia in grease) soluble in water) Thus, soap particles can dissolve pantly in grease and partly int Water.

(b)Soap works.In. The main ways in

tieaning:

the dirt of grease. That is, it breaks down the dirt or grease into to be tiny droplets so as washed away be water. Thus, soap is an emulsifying agent.

(1)It emulsifies

*150

Fabric

soap solution

+

soap ion

Repulslar

Is)

soap particle

water maloaula

scum

Soap Solution

7. Using Soaps 7.1Advantages

and

vetted surface

Low surface tehsics due to the weakening. of the forces between water molecules; by the presence of soap particles and the repulsion between the hydropovic ends.. 4: Synthetic (Soapless Detergents 4.1Synthetic detergents have

structure similar to the soap out their hydrophobic talls ard hydropinilic Feads are different from that of the soap..

e.g.

4.2The

Hydraphoole tail

(a)Good cleaning agent, (b)tittle

effect

organisms.,

problem.

nence

living"

pollution

(c)Biodegradable, 1.e decomposed by

bacteria.:

7.20isadvantages

(a)forming scum in, hard water; {b}Not suitable in strongly: acidic.

medium.

(c) Increasing Gemand" án fats/ails

that conex be used as food.

B. Using Synthetic Detergents 8.1Advantages,

in hard

{a}Not forming any scum loatc head

water, hydrophobic hydrophilic yuparts of a synthetic detergent have to be joined together using chemical reactions.

4.3Petroleum is the main source of the material s'': for aaking: synthetic

detergents..

4.4The cleaning action. of synthetic similar to that of the

soaps and Detergents

Gain alcohols within ther

-C-03

cjean.

•1 infage

The dier is proken up Into. croplets which remain separated due to the repulsion between the ́stoflaniy-charged' tonic heads of

soap particles.

(2)It lowers the surface tension

of water and

makes Water

better wetting substance.

a

services. The. producers or sellers who bay, the Laxes, Tay shift the tax burden to someone. else. Usually indirect taxes are expenditure-based.

Principles of Taxation

A. good taxation systen should consider. the following. 7 principles:

1. Equality

There may be 2 views on equality. One is that a person should be tased according to his ability. Another is that a person should be, taxed according to the benefit he

2. Certainty

tax obligation

:Father or foa

(b)Bleaching agen

(c)Anhydrous. Na, Sto keep

powder 生

(d)NajPoy to remove Mg2+ and Ce2

hard water. 6.‘Hard' and 'soft' water 6.1lard. water. is. one consisting of

possible.

·Aims of Taxation

Taxat on may have the following 4 aims: 1. Raising. goveriment revenue

government requires money provide puclic services. Through. 'taxation ft. may get the ioney. For

its expenditure.

(b)Can be used in acidic medium. (c)tess demand on fats, oils. 8.20isadvantages.

(a)Toxic to aquatic lives.

thus

soaps

and

(b)Synthetic detergents consisting cof branched hydrncarbon chains

non-biodegradable, are causing environmental pollution.

9. Pollutions caused:

Detergents. Phosphates. in most detergents. stimulate the growth of algae which use up most of the dissolved oxygen and hence kn the aquatic.organisms (due to lack or oxygen).

for Detergents

detergents ' form a lather foam bbles) when stirred with soft

10.2Soaps do not form lather with hard.

water

readily

synthetic

as

detergents.

as

Other Effects of Taxation

Taxation may have 2. other effects::

Prect on work effort

The effect on work effort consists 42 opposing effects: income, cceract and subst tution effect -to come effect

the means that taxpayer will work more so as to earn. more income to compensate the loss in income due to the tax. Substitution effect means that the taxpayer will work Tess and will substitute leisure for work effort.. because he thinks

not it is worthwhile to work so hard. The ultimate effect of taxation on work depends on the relative strength of these 2

if effects.

the Substitution effect is greater than income effect, the taxpayer will work less. But if the substitution effect is less than income effect, the taxpayer will work more..

2. Influencing. Consumption behaviour

When a government considers some. goods,e.g. cigarette, harm十口佛克 people, it may impose a jax, on so as to discourage therdalefand fci it. On the contrarye encourage the senia som對 by reducing the taxe

3.

Re-distribution of come

KONG PUBLIC

1. Direct taxes (1)

Direct: taxes

are those taxes which are levied on a person. The person who is taxed cannot shift the tax burden to anyone cise. Usually direct taxes are income-based.

2. Indirect taxes.

Indirect taxes are those taxes. which are levied on goods or

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should be stated clearly. It should

3. Convenience

The payment and the collection of a tax should be convenient to the parties concerned.

44 Economy

The administrative costs of a tax collection should be as small, as

Through taxation a government may Collect money from the higher dacone group and use the money to and the lower income group.

4.Improving balance of payments.

country faces an palance of payment,

unfavourable

its government may impose-tax on imports. SO as to discourage people's spending

imported

goods.

2,

Effect on investment

Profits tax may lower a fire's profit. Thus the firm will have less money for further investment. Besides, as the: tax makes the business Tess rewarding, the firm may have little interest to invest

more.

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