1965-05-20 — Page 14

真二第四第

四期塞

日十二月五年五六九一磨公年四十五國民中

日十二月四年巳乙愛付

1

WAH KIU YAT PO

#

Define:

normal solution.

molar solution,

英中會考自然科學試題

EDUCATION DEPARTMENT HONG KONG

ENGLISH SCHOOL CERTIFICATE EXAMINATION. 1965

GENERAL SCIENCE

Time allowed → Two hours and thirty-rosaute

PART 1 (75 marks).

CANDIDATE'S NO.

ALL answörs in Part I must be written in the space provided.

of the paper must be handed in with your answer book..

Pari

Candidates are advised to try to complete this section in 45 minutes.)

Symbols and formulae may only be used in chemical equations, All names must be written in full.

How many grams of sulphuric acid, acetic acid (CH,COOH), or}

odium hydroxide are contained respectively int

litre of 0, 5N sulphuric acid. ilitre of decimolar acetic acid

i 100 cas. of ZN sodium hydroxida, iv. † litze M/2 sulphuric acid.

Calculations:

and 12.

(<)

The process is mane pasardig Decaus

is only alightly soluble,

EART B (120 marks)

Instructions to candidates).

Answer FOUR questions only. Each carries 30 marks. Start each question on a new page of the answer-book, Write the numbers of the questions clearly in the margin. Names of substances must be written in fuli, Symbols and formulae may be used only in equations.

In calculations; all relevant steps and working must be shown. Write clearly and arrange your work neatly.

States

Gay Lussac's Law."

Avogadro's Hypothesis.

(2)

Name, two elements which burn in air to forto acidic oxides:

I and two new our in air to form basic oxides:

(b))

Demice the relationship between molecular weight and vapour density,

A gas mixture containing 20 ees. of carbon monoxide and 40 cca.

(o)

Name the substances formed when the acidic oxides' made t burning the elements given in (a) are dissolved in water. /

XO is a basic oxide,

with hydrochloric acid,

Equation:

Li

Write an equation to show its reaction

Draw and tabel a diagram of the apparatus you would use to prepare hydrogen from steam,

State what modifications you would need to make in the apparatus if you wished to prepare dry hydrogen. (Do not draw another diagram).

What is the effect of prolonged exposure of a clean iron surface to”

1 dry air,

1 humid air,

Answers:¡

231- rain water

pure water, 71, 0, containing no dissolved sustance.

What conclusion do you draw from the results of these experiments 7

Answers:

Name the metals present in the alleys below

(d)

of oxygen was exploded. After cooling to room temperature the volume of the remaining gas was 50 ces, but was reduced to 30 cca. after shaking with a solution of caustic soda,

4

Show that these figures are in agreement with the law of Gay Lussac.

On heating 7.5 gms, of a solid, 1680 cas. of a gas et N, T. P. and 4.2 gms. of residue were produced.

Calculate the molecular weight of the gas, and state the assumption used in the calculation,

Describe how water can acquire, by natural means,"

temporary hardness. 精 " permanent hardness,)

Outline and explain a chemical method for removing both kinds of T hardness simultaneously, and a chemical method which removes only temporary hardness.

Describe how you would discover whether a sample of water contained temporary, permanent or bath kinds of hardness.

QUESTION

soldes

Ans:

Kiantian one characteristic test, and one Industrial use for hydrogem

What special properties of the alloy known as "type metal" ma especially suitable for use in the printing industry ? Answer:

What is an alloy

{tame all the constituents of (1) duralumin, and (ii) type metal" --

typo-metai

(2)] | [Name the alloys made of

15 para destes and fluc

lead and tim

Name, in order, the elements whose atomic numbers range from a to

Draw diagrams of the shell (ie, orbitalį structure of atoma of hydrogen, carbon, sodium, calcium,

Hydroge

Carbon

· Name]

seride

formuler

FOIL

What is meant by (a) unsaturated compound, (b) addition compound?

Ang

11. Describe exactly what you would observe when (a) water le added slowly

to freshly prepared quicklime, (b) a burning candle is lowered into » jar of chlorine, and (c) washing soda crystals are heated gradually high temperature,

VOTE:

POTARLIQ

TEMPER

(Sodium:

Calcium

Defines

Answer:

electrolyte.

Il cathode,

11 weak acid,

Draw a neat and clearly labelled diagram to illustrate the laboratory preparation of dry ammonia gas, and give the equation for the reactím

Ammonia can be oxidised directly by hoi copper oxide, Name the products of the reaction, and state an important conclusion which can be drawn from the result of this experiment.

Diagram:

[Answered.

Equation:,

Products are:.

Conclusion drawn,

The same current is passed for the same time during the electrolysem of a solution of a silver salt and acidulated water respectively.' in, the former, a deposit of 2, 16 gms, of silver was produced; in the latter there was an evolution of 224 ces. of hydrogen at N, T. P. Calculate the equivalent of silver (OR the atomic weight of silvern,J and explain the principles used in the calculation,

Calculation:

Complete the following equations:

CONH + HO

(b)

(al

LC)

NaCl + NH HCO

(b)

[b]

These equations represent the main reactions of the

process for manufacturing

The three badic raw materials used in the process are l,.

"A white powder containing two substances derived from the same

metal was seen to dissolve partially when shaken with water, producing an alkaline solution, However, the white powder dissolved completely. In dilure hydrochloric acid. producing a gas which gave a white precipitate with lime-water. On adding excess sodium carbonate solution to the resulting acid solution, a white precipitate was formed, Finally, a sample of the original powder was heated with ammonium chloride yielding a gas which gave dense white fumes on contact with the stopper of a hydrochloric acid bottle.

Explain each of the observations noted above, and hence auggest the possible composition of the white powder.

The accompanying graph show's the solubility curves for potassium nitrate and potassium chloride. Use the graph to anawer the following questions as accurately as possible.

What is the solubility of potassium nitrate at 7

(a) 65°C..

(b) 35°C. ↑

What is the solubility of potassium ènioride as

(a) 85°C,

(b) 15°C.

What will be the effect of trying to dissolve a mixture containing 75 gms." of the nitrate and 50 gms., of the. chloride in 100 gms, of water maintained at 50°C,

2

you were asked to make 100 gms, of a saturated solutio of the nitrate in water at 25°C., what weights of nitrate ans. water would you use ?!

If you were to cool to 35*C, the solution made in iv; what weight of nitrate would crystallise out?

What information can be obtained from the point of Intersection of the two curves?

Write down the general formula of the paraffins, and the graphic formulae (e, showing all valency bonda) of the first three membe of the series, together with their names,

Describe the preparation and properties of the simplest paraffin, and show by means of equations how it forms substitution products with a halogen, Name these products.

State briefly how you would discriminate between ethylene and j STELIERS,

Explanationt)

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