真二第張五第日七初月四年丑発歷
1973英文中學會考試題預習專欄
WA ME NKARENA
化學科
(廿九)
Chemistry (29)
Solution for last week
TI
AMAMO
6000000
T
HUCHU
O. R
No. of Hydrogen: No. of Carbon:
14.28 85.72
12
14.28 7.14
Therefore the empirical formular of X is CH2
(ii) Molecular weight
2 x Vapour density
2 x 21
42
Let (CH2) be the molecula
formula,
(12 + 2) =
Therefore the molecular formula is CH6.
The structural formula is
HHH
Its name is propylene
(iii) 203H6 + 90%
6002 + 6H20
• 9 = 10 c... : Y c.c. (y be the volume of oxygen
required)
(iv) a. It combines with hydrogen
when passed over a catalyst of heated platinum
CH6 H2
озна
It reacts with chlorine under sunlight to form an additional product.
C3H6 + Cl2 C3H6C12
dichloropropan
It also forms additional product when hydrogen chlor- ide is passed slowly over it. C3H6 + HCl →→→
HACL
d. It is absorbed by concent- rated sulphuric acid":
C3H6 + H2SO
Organic chemistry (2)
озн
C HHSO
The Monohydric Alcohols.
The term monohydric alcohol indicates an alcohol possessing one hydroxyl (OH), group.
The monohydric alcohols consti -tute a homologeous series of general formula C H.
OH
the
first four membergcohol)
Methanol (or mei yl
Сизон
Ethanol (or ethyl alcohol):
C2H5OH
C
CHOH
Propanols (or propyl alcohols,
normal or iso
Butenols (or butyl alcohols, four isomers) OH OH CHOH
Classification of monohydric alcohols
They are classified as primary secondary and tetrary alcohols. according to whether the carbon atom which is combined with the hydroxyl group, OH, is combined with one, two or three carbon atoms respectively.
General methods of preparation alcohols
1. Hydrolysis of alkyl halides
The alkyl halide is boiled under reflux with aqueous caustic alkali, e.g.,
-O E ̧Br + KOH —○2H5OH + KBr
Reduction of carboxylic acids or their eaters
WAH KIU YAT PO
報日僑華
三期星 ®
日九月五年三七九一层公年二十六國民華中 育教僑華
HSO
1978
CHHSOC2H4+ H2SO4
中文中纜會考試題預習專欄
英文科
(廿九)
徐有祿。
The reducing agent is lithium aluminium hydride. The acid or ester and the reducing agent are both used cold in dry ester as solvent, under reflux» Later, water is added to remove excess of hydride and ditute sulphuric acid to release the free alcohol from intermediate products. The reactions are complex but equivalent finally to:
RCOOH + 4(H) →→→→→RCH2OH + RCOOR, + 4(H)- RCH OH +
By fermentation
By the fermentation of glucose or sugar with a suitable organic catalyst (enzyme). The catalyst used is zymase (yeast)
yeast C126
20H OH + 200
The fermentation goes best at a temperature of 25° 30°C. The product is distilled, and the alcohol collected, dried over quickline and redistilled
Properties of the Primary Alcohols Physical -- The simple alcohols are liquids. They are very soluble in water and in organic solvents such as ether
Chemical
ethanol
illustrated by
properties of the hydroxyl group
a) with sodium or potassium
In the cold, effervescence occurs and hydrogen is evolved.
A deliquescent
white solid is left, sodium ethoxide,
200
OH + 2Na2CH2ONa + H2↑
b) Ester formation with acids. -The alcohol is heated under reflux with an anhydr ous organic acid and a little concentrated sulphur- ic acid, or dry hydrogen chloride, as catalyst. The product is an ester.
CH
CHCOO
COOH + HỌC, H,= GH COOC, H,
H2O
Action with phosphorus pentachloride -- Vigorous reaction occurs in the cold "Steamy" fumes of hydrogen chloride are evolved togeth er with an al-yl chloride.
C2H5OH + PC15
+POC1
+H01
phosphorus trichloride giver a similar reaction. 3C2H5OH + 2PC1302H01
2. Oxidation
203 3HC
Primary alcohol oxidises in two distinct stages, first to an aldehyde, then to a carboxy lic acid, with no less of carbon.
RCH OH + (0)
RCHO + H2O
RCOOR
RCHO + (0)
CHCH2OH + (0):
CH3
CHO + (O)
3. Dehydration
CH CHO + H2O
Acetaldehyde CH COOH Acetic acid
Ethyl alcohol can be made to dehydrate in two distinct ways by choice of conditions and these should be carefully noted.
a) To ether
Ethanol in excess Concentrated sulphuric
acid Heat to 145°C.
b) To ethylene
Ethanol
Concentrated sulphuric
acid in excess Heat to 180°C. First stage for both:
CHOH + H2SO
HSO4 + H2O
With excess ethanol: C2HHSO4 + CH5OH (C2H)20
4. Dehydrogenation
Primary alcohols can often coverted to aldehydes by passage over copper ganze
(Catalyst) at 30000. Hydrogen is removed as the element.
H2t
RCH OH ) RCHO
e.g. CH2CH2OH
5. Burning
-- CH CHO + H
Ethyl 1 alcohol burns in air, and in oxygen:
e•E• CH CH2OH + 302
Saturated Monocar (Fatty acids)
3H 0 + 2002 (4 His
ylic acids
Saturated monocarboxylic acids form a homologous series of which the general molecular formula is CHCOOH, where
n is 0,1,2,3, etc
Formic acid
Acetic acid
CH3C
HCOOH соон
Propionic acid C2HCOOH
Method of prepara
By oxidation of primary alcohols
All the simpler primary alcohols and aldehydes are oxidis- ed readily to the corresponding. carboxylic acids.
RGH2OH + (0)- PCHO + H2O
ROHO+ (0)
RCOOH
CH_CH OH + (0) →→ CH CHCH2O
сна сно (0)
CH3CHO + H2O CH COOH Acetic acid
Properties of the fatty acids
Physical The first two fatty
acids are liquids in ordinary conditions. Both of these acids mix with water in any proportions. With lengthen- ing of the carbon chain, the acids become solid and the solubility in water decreases
Chemical --
Acidic properties -- All the fatty acids are weak,
a) production of colour change in indicators, e.g., litmus from blue to red
b) Neutralisation of a base to produce a salt and water only, e.g.,
RCOOH + KOH- RCOOK + H2O
c) Liberation of hydrogen with strongly electropositive metals.
2(CH,COOH) + Mg
Mg(CH, COO)2 + H2↑
d) Liberation of carbon dioxide with carbonates and bicarbon -ates.
e.g.
NaCO3 + 2CH3COOH →→→→
2CH COONE +H2O
Ester formation
+ CO
The anhydrous acid is boiled under reflux with an alcohol and with concentrated sulphuric acid or dry hydrogen chloride as catalyst. RCOOH + ROH
RCOOR + HO
CH3COOH + CHOH
CH COOCH
+ H2O
3. Action with phosphorus
pentachloride, and trichloride.
Phosphorus pentachloride. reacts quite rapidly at ordin- ary temperature with the simpler acids, liberating hydrogen chloride and forming the corresponding acyl chloride
RCOOH PO15 →→RCOC1 + POC13
+HC1
Phosphorus trichloride gives the acyl chloride and hydrogen chloride, too, but less rapidly. and usually requires steam-heat 3RCOOH + 2P0133RC001 + P203
(未兆明日續)
3HCL
English (29)
The answers to last week's exer
cise are as follows:
(a) postponed
(b. it will start.
(c) takes
(d) neither did I
(g) s
somewhere else
on
spend
0000000
Read the following passage care- "fully and write down suitable
prepositions for (a), (b), (c) etc. Do not copy the passage.
The chairman turning (a), the secretary, told him to put the
Then he proposal (b) record. asked whether anyone (c) the meet-
He ing had any objection (a) it. was surprised (e) the show. (f); hands (g) response and he rose (h) his seat to count them. Still determined to have the proposal passed, he said he would repeat. it (i) the benefit (j) those who could not understand its importance.
Write out the correct tenses, active or passive, of the verbs in brackets in the following sentences:
(a) The accident not (occur) if
he (check) the brake of his car before going for a ride. (b) The unfortunate man, who
(fall) from the tenth storey, (catch) halfway by a canopy extending from the window. (c) If you (be) the director of
the department, what you (do) (d) In two more hours our car
(complete) its trip round the New Territories and the sun.. (set) by that time.
(e) Every evening he (visit) the
theatre but never (buy) a ticket.
Insert "helping verbs" to complete the following questions: (a) Why
you not tried to persuade him to join us? (b) Where
(c)
he leave the pen- cil case yesterday?
he quite happy with his present job?
the boy holding the tray when he slipped? (e) Who: take care of the baby when she is gone?
(a) How
(£)
(e)
the girl shown any interest when you showed her the necklace?
the dog playing in the garden when it bit you? (h) Why
the pupils being detained now? (1)
your brother like straw- berry jam?
we been told of the regulations of this school?.
Combine each of the following group of sentences into ONE sentence:
(a) Mr. Jacob attended a village
school in Scotland.
He was the author of this book.
He died recently.
(b) He saw the big fish in the
stream.
He sat down on a rock on the bank.
He tried to think of a way to catch it.
Put the first sentence (a) into Indirect speech and the second (e) into Direct speech: (d) Before going out, Mr. Banner
said to his wife: "If I am not home by 11 o'clock, tele- phone me at the office.": (e) The bus conductor told the
passengers to wait till the bus had stopped before they got off.
Candidates may find the exercises in this week's column somewhat different from those in previous weeks columns, but they are not simpler. They are just
Candidates as full of pitfalls. are therefore warned that they must approach every question with the same caution although they maj find one question simpler than another on the surface. They should bear this in mind when they are doing the exercises, as well an attempting the questions in Paper.