1966-06-02 — Page 15

TEXBOX

百四十四年午丙薹買

WAH KIU YAT PO

12: 期

英中會考生物科答案 瓶)

徐錫禧

華僑教育

英中會考化學科答案

王錦釗。

ENGLISH SCHOOL CERTIFICATE 1966 INSWERS ΤΟ CHEMISTRY EXAMINATION

SECTION B

2. (a) State what you would see and explain what happens when:

(1) Concentrated nitric acid is added a little at a time

to copper turnings in a beaker until no further change takes place.

When concentrated natric is adde¤ à Little at a time to copper turnings in a beaker, effervescence occurs and dense brown fumes are given offs Gradually the copper disappears, and when no further change takes place, all the copper will have disappeared, and a blue solution is left in the beaker,

The nitric acid oxidises the copper to copper nitrate, which forms a blue solution, and nitric acid itself is reduced to nitrogen peroxide, which is a brown gas. The equation for the reaction ibr-

Cu + HNOX = ̈ ̈ ̈ Cũ (NO3)2 + ̈2N02

**2K 20 (ii) A piece of burning magnesium is lowered into a

carbon dioxide,

JAY ME

When a piece of burning magnesium ribbon is lowered into a jar of carbon dioxide, it continues to burn brilliantly with the formation of dense white fumes, Black specks are obtained on the sides and bottom of the gas: jar..

The burning magnesium burns at a temperature which is high enough to decompose carbon dioxide into carbon and oxygen. The black specks obtained is the carbon so formed. The oxygen supports the combustion of magnesium forming magnesium oxide, a white solid,

The equaltion for the reaction ist

2 Mg CO2

2 MgO

C

(1) A stream of chlorine is passed into a solution of ferrous

chloride. When a stream of chlorine is passed into a solution ferrous chloride, the pale green solution is turned into a light brown solution.

The chlorine oxidises ferrous chloride pale gre solution) to ferric chlorinde (light brown selution). The equation for the reaction is:-

2 FeCl2 = 2FeCl

(b) Describe one good chemical test in each case for distinguishing

between the following pairs of substances:

(1) Sodium carbonate and sodium bicarbonate.

To a small quantity of an aqueous solution of each substance in a test-tube, add magnesium sulphate sulphate solution **/*

In the test-tube containing sodium carbonate, a heavy wh precipitate of magnesium carbonate will be formed,

Na2 C0, + Mg 30

While in the test-tube containing sodium bicarbonate, no apparent chemical change takes place, as the resulting solution contains magnesium bicarbonate which is soluble in water.

Mg SO,

ים

Mg (HCO3)2 + Na230,

Copper oxide and manganese dioxide. Put a small quantity of the black solids into two hard- glass test-tubes. Add concentrated hydrochloric acid to each, and heat gently. In the test-tube containing manganese dioxide, a green gas, chlorine is evolved, whic tüme starch-lodide paper blue,

0,4 H MnC12H20 C12,

"Proposed answer for 8.8.8.9.C.R-2966.

a) Make a list of Bight named multicellular organisms (plants and

animals) that you have found in any one named -habitat (or in a balanced aquarium) you have studied.

The.

The typical multicellular organisms in pond life are an follows:

1, Hydra

2, Pond shails of various, form

3. Fish iya, 961s

4. Frogs in various stage.

5. Spkrogyra

6.

Duckwaeda

7. Water lilies

8. Canadian pond weeds.:

b) Give a brief illustrated account of the life history and

habits of one plant and one animal from your list.

Spirogyra is a multicellular plant found along the sides of! fresh water ponds or slow-ruining streems,

Its life history can be classified into two typas bacarding to conditions

The mature spirogyra filament would increase in length by cell division and elongation in gongitudinal direction only, After the wholear division the plant cell by forming a cross wall divides into two young cells which develop its cylindrical-shape structure. Then each young cell slowly grows in length to the normal isze.

Vegetative Reproduction When condition 13, favourable parts of the mature plent body become, separated to give rise to new individual without any abvious change in the protoplasm. Then the filamenta separate into two shorter lengths of the filament. The reproductive method is termed. fragmentation.

Sexual Reproduction:

Usually when condition is unfavourable or by chande the two mature spirogyra filaments arrange parallel to each other conjugation occurs, The co is of the two separate filaments would link together by forming a conjugation tube. The contents of the two linked cells shrink the chloroplasta. disintegrate, the cross walls are then dissolved. The content of the oell as moved to the other cell by passing through the conjugator cube. Then the two nuclei fuse together. The fusion of two cells is termed fertilization. After the result of fertilization an ellipsoidal zygospore is formed, 1 continues to develop as is set free by decaying the old centralla of the filament. It is able to resist adverse condition or

is carried by animal feet or wind to a suitable condition where

it burst out of its zygospore wall to for a new filament by cell division.

HA

Conjugation

tube

日二月六年六六九一麻公年五十五國民華中

The life history and habitat of a multicellular animat (Froz)'s Habitat:

Frog is found in fresh water ponds, lakes, planted fields or ditches.

Breeding season: It is around March or April each year.

Its life history can be divided into the following atagant

1. Mating In spring the mature male frpge ride a pick-a- back

fashion on the mature female, m

2.

Egg laying after mating the female frog lag 1000-2000 egge on the shallow pond Lottom. Then the male frog sheds sperm over tham

3. Fertilization when the fusion of a male sperm and a female

egg starts fertilization is said to take place. Development is the process of charge during which the fertilized egg becomes a multicellular frog.

(1) Ambryo days altar fertilization the zygote develops and has tail, nead arid cement gland. The energy and raw materials for growth are supplied from its yolk while ozygen for respiration diffuses from the pond. water through the egg membranes and surface of the i enbryo.

(ii) Larva 2-3 days after natching, tadpole is formed. Tail

lengthens mouth and external gills start to functions by inhaling dissolved oxygen through external gills. The tadpole is fed by, pondweeds,

Mouth

2 weeds after hatching, the operculum of the tadpole.. begins to grow and interrial gills emerged...

3 month after hatching, formation of hind limbs first appears and the tadpole inhales diseclved ozygen through internal gills. The animal is graduall changed to take in carnivorous dist,

2 months after hatching lungs develop and the animal pay frequent visits to surface of the porida.

3 months after hatching the animal casts skin and young frog is formed after the complete absorption of the tai It then leaves the water and try to live on land by Innaling free oxygen from the atmosphere through..akin and mucous membrane of mouth and lungs. The young frog Tands on worms, snaile and flies.

-Nerly botched topole.

Rudiment of pe

Worth

ent glach

monining yolks.

cement gland Enteral githe

sport

ntemal gil Mouth

Frai lint

-Hind limb

2 KI

2KC1

(turns stareh blus)

In the other test-tube, no gas is given off, but solution of cupric chloride is formed,

Cu 0. 2401

[ (111) Chalk and slaked-line.

Put a small quantity of each solid into two separate test- tubes and add dilute hydrochloric acid to each. In the test -tube containing chalk, vigorous offervescence takes. place with the evolution of a gas, carbon dioxide, which turno lime-water milky...

Ca Co 2HC1 CaCl⚫ CO2 H2O

In the other test tube, no effervescence occurs,

but the solid also dissolves in the dilute acid forming.

clear solution of calcium chloride,

Ca(OH), + 2401

CaCl2 + 2H20

Question 4 (a) You are provided with potassium nitrate, ammonium

chloride, slaked-lime and concentrated sulphuric. "acid, but no other reagents, Sugest how you would

obtain (1) nitric acid, (li) ammonia, (iii) oxygen.

(1) Heat a mixture of concentrated sulphuric acid and potassium

nitrate in a retort Nitric acid vapour is given off, which is condensed to a liquid by cooling the receiver under the tap.

Process of Conjugation of Splenor HR XI

外衆度强,的批 講五論有英之主十三開,共解對計定杰之形, 偡非下 線多好轩稱: 甯下篩報體

A young adults)

stages in the development)

Figures of Developpent of a forg

END

部修進外校學大文中 注對程課新項三天兩明今

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部中

以窑作一分式名

夺可必須點於 台粥 試用須交到;今年

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大能况理開具開

水罐;序番組市工

下篇篇諜。赠上學期演期對括代阻 在共演時

「當代英

中中會考

明日開始

·考生宜記各項應試

***

H250% KNO

5.

· KHS (13) An intimate mixture of ammonium chloride and slaked-line

(with the slaked-line in excess) is heated in a harc glass test-cube and the gas evolved is collected in gas jars by upward delivery;

2NH C3+

Ca(OH)2 → CaCl2 * 2NH2** 2H20 (111) Some potassium nitrate is put into a hard-glass rest-tube

and heated strongly. The nitrate decomposes with evolution of oxygen. The gas is collected in gas-Jars over water

2KNO3 • 2KNO

(b) Stäte briefly the industrial preparation of nitric

acid, starting from at

Nitric acid is annafactured from ammonia by the Ammonia Oxidation Process Purified ammonia gas, made by the Haber Process, is passed with excess of air over platinu wire gauze (catalyst) at red heat, the temperature being about 900°C. The ammonia is oxidised to nitric oxide.

+502

4ND 6H20

The nitric ocide is then rapidly cooled and ia mixed with more air to form nitrogen dioxide:

2W4 +02

*

2N02

The nitrogen dioxide, with still more air, is passed into hot water, and a 60% solution of nitric acid is produced

2H20 ANO2+02:

HNO

(0) Describe what happens when: (1) ammonis gas reacts with Schlorine gas, (11) ammonia solution is added to ferrie

chloride solution.

(i) Ammonia gas reduces chlorine gas to white fumes of ammonium

chloride, while the ammonia itself is oxidiseo to nitrogen

BNH3 + 3012 6NH C1 + N2

If the chlorine is in excess, the highly explosive compound, nitrogen trichloride NC1; will also be formed,

Fe

(1) When ammonia solution le added to ferric chloride solution,

'a brow gelatinous precipitate of ferric hydroxide is formed,

3 NH, OH FeCI

(OH)3 + +

3NHL CI uestion (a) 2.45 gm. H2 50 is contained in 5000.c. solution.

26.5 c.c. of the sulphuric acid solution required 30 c.c. of sodium bicarbonate, solution for: neutralization. Calculate the strength of the sodium bicarbonate solution in grams per litre.

2Na HOU3

Naz SO

2x84

The aquivalent weight of sulphuric asid

the normality of NARCO solition

0.18

0.265

g per litre)

7.42 ga per litre.

(b) What is the volume of carbon dioxide evolved at N.T.P.

when

5 gms of calcium carbonate is added to 60 c.c.j N-HCl solution? What weight of calcium carbonate would remain?.

CaCO, + 2HC1 - Ca 012

100 gms

2 litres N-solution 1 litre N-solution.

CO2 + H2 0?

22.4 Litres at N.T.P.). 11.2 litres at N.T.P.

Volume of CO2 at N.T.P. obtained from 1 titre. N-HC1 - 11.2 Titres

600 c. N-H01 - (11.2 x 0.06)

litre. 0.672 litre,

672 ml.

200, 28-01

Weight of CaCO, that will react with i litre N-HO1 -

60 c.c. N-401 -

50 g A

(50 x 0.06)

The equivalent weight of sodium bicarbonate - Bh

Strength of 30, Solution

2:45 gm in 100 c c. solution 4.9 gmper. litre solution

the normality of H2SO Solutions:

0.1 N

·30.6.

of NaHCO solation,

Original wt of calcium carbonate

wt. of calcium carbonate left

gm

(53) g.

2 Sus

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