1982-03-29 — Page 22

'頁二第張六第日五初月三年戌壬曬夏 WAH KILI YAT PO

1982

Mass of carbon in

1.48 g of Z

mass of carbon in

2.64 g of CO,, formed

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on

化

學

2.64

(四)

12 x

0.72

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Chemistry (24)

Reginald W.

"MILL & DALE PRESS LTD,

Solution to

34

4(a)

(1) A is copper(11)

carbonate;

Bi

B is copper(11)

chloride solution;

C is carbon dioxide;

D is copper(II) oxide;

E is

copper.

CuCl2+,0C,

(2) Cu€0. →→ CL{ +CO2 (3) 2cuo+C -C2+2Cu

Molar mass of C02=44 gmol

Molar mass o H0-18 gmol

Mass of hydrogen in

1.48 g of Z

Mass of hydrogen in

1,08 g of water

formed on combustion

1.08

18

0,12 g

1982

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PHYSICS (25)

I. K. Lo

MILL & DALE PRESS LTD

Revision Test

allowed: One hour

and 30 min,

Answer SIX questions choosing, at least ONE. from each section. Each question carries equal · marks, All answers to problems should be given in S.I. unita,”

SECTION A MECHANICS AND

PROPERTIES OF MATTER.

(When necessary, take the

acceleration due to. gravity

10mg-2

Figure

Figure 2

In figurer 1, two metal spheres A and B are suspended from X and Y respectively by two strings of eqnal Tength. The strings are long, inextensible and of negligible máss, A and B have the same radius r and” the- seperation of X and Y is 2r. The points XY and the centres of the spheres are in the

mass of oxygen in

1.48 g of Z

(1.48-0.72-0.12) g 0.74 g

Mole ratio of C:11:0 0.72

0.12

0.64

12

0.06 : 0.12

10 0.04

3: 6:2

Hence, the empirical formula of. Zis

CH02

(ii) Molar maes of ï

0.296 x

74gmol

24000

relative molecular mass of 2 is 74.

(iii) Let the molecular

formula of Z be

(G2H2Ug) n

Then, relative molecular mass

740

74 (as calculated

above.)

Hence, the

molecular formula

of Z is C-H

C-602-

(iv) The three compounds

with this molecular formula ore

(1) CHL CH2COOH

same vertical plane.

The mass of is 2kg

and it is pulled aside

so that it is 0,5m above its lowest

• The

released

position. The mass of Bis 1kg and it is pulled aside so that it is 1.25m above its lowest pogi Lion.

are then the same time, the spheres. callide. with each other and the naximum height reached by B after collision is 0.8m (soe figure 2) (a) Explain briefly why the spheres will collide at their lowest positions.

(2 marks)

(1) What are the

[(b)

velocities of the spheres just before collision?U (fi)What are the

velocities of the spheres just after collision? (ifi)Find the maximum

height reached by A after collision, (iv)If when A collides

head-on with B, the two spheres remain in contact for 0.2- seconds, find the average force an during the callision. (v) Pind the energy lost uuring, the collision. In" what: form will the fost energy dissipated?

(8 marks)

så amidorm planck AB of

Length 12m and mass 50kg rests on two supports P and at positions 3m and 9m from one end A. A món of mass 75kg stands on the planck 1 metre from 6 and 4m from H as shown in figure 3.

3m

5m

Эт

Figure 3

Find the reactions at P and -9.

(b) If, the man walks

tovards D, find,

報日橋華

propanoic acid

(2) CICOOCH

methyl ethanoate

(5) Heo CI,CIL,

ethyl methanoate

Solution to î.

(1)(1) When the pressure

(b)

is increased, the rate of the forward reaction and that of the backward reaction are increased to the same extent.

(2) When the pressure is increased, the position of equilibrium is not affected because the number of: moles (or volumes) of reactants and products are the

same

This indicates that the forward reactioni is endothermic because an increase in temperature, would increase the rate of the forward reaction to a greater extent than the backward- reaction does.

(1) It is because,

lead(II) compounds cause lead poisoning, so, they are not used in painting children. toys.

Copper is slowly

how far near from I can be reached before the planck. vilts.

What factors will

affect the efficiency of a single string pulley system? State briefly how the efficiency is affected by each of these factors,

(b) A block and tackle

consisting of three

(iii

一期星

oxidized by atmospheric oxygen

The copper(II) oxide

formed then combines. with carbon dioxide. and, water nöisture in air to give hydrated copper(II) Carbonate which is green in

colour This is because when sulphur

trioxide dissolves in water, it reacts water to give hydronium iôns.

4504

Since H-07 ions are responsible for acidic properties, so, aqueous solution of sulphur. trioxide can turn litmus paper red.

日九十月三年二八九一届公年一十七國民華中 育教僑華

(iv) The crystal observed

is silver metal. This is because copper is below zine but above silver in the activity series, meaning that copper is less reactive than than Zinc, but more. reactive than silver. As a result copper cannot displace zinc. from zine sulphate solution, but it can displace silver from. silver nitrate. solution

Solution to

:(a):

(1) X: CH2CH2OH ethanol

Y: CH2COMF

ethanoic acid CH COUCH, CH ethyl ethanonte

(ii) (1) CH2CHLOH+? (0) →CH_COO!!+IL,0

(2) CH=CH_©H+PC15

> CH2CH2C1+PQC1,

(3) CH2COOH!+PC1

CE, COC1 PUCA,

+JC 1

(4) CH2CH2OB+CH C001

CH-COOCH,CH2

The organic compound produced in (2) is chloroethane and that in (3) is ethanoyi chloride..

Effervescence takes place asta colour-s' "Tesk is evolved.

+MI

(*)(1) The As

ethene.

⋅ (2) CH=CH12OH

The bromine solution wouïd decolourized

Mathematics (Sy11, 2)(25) 7. Ia × and are the

C.P. Man

ML11 & Dale Press Ltd

Exercise 11 Auswer all questions in Section A sud any five questions in Section B. Section A

1. Given that 0 <0≤180°

solve the equation 2sin(39-45°)=+√2.

fixed and two movable 2. Three consecutive

pulleys is used to raise an aluminium cube which is completely immersed in water (density 1000kgm2) as shown in figure. If the volume of the cube is* 10m3, the effort applied to machine is 80%

alum:

Aluminiun

Cube

density of

2.5)

Effort

water

-density

Figure 4. (1) what is the velocity

ratio of the system? (ii)What is the upthrust

of vater on the aluminium cube, (iii)Neglecting the

resistance of water find the accelera tion of the cube while it is moving in water.

(iv)ind, approximately,

the position af which the cube will finally stay. (v) What additional

effort is required to apply 10, the system in order to push the whole cube ou t

of water?.

數學

(廿五)

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terns of a G.P, have a product of 125. The third term is nine; times the first, Find these three terms.

In the figure, AOB is a diameter of the semicircle, ceutre 0 radius icon. If ZABC=2;

find the area of the shaded portion in terms of π?

At what price must n stojkeeper murk an article costing $180 so that he can allow a discount of 10% on the marked price and. still make a profit of 10% on the cost price?

In the figure, PQ:QB= 2:5. All-8cm, AM-14cm. Find AK

15

A

In the figure, DC is the diameter of the circle. If ZDAC÷15, 4BCD-40% find 4CED.

routs of the equation x +kx+12=0 and x=5p Lind all the possible values of k.

8. Ife is an acute angle

and

calculate

without the use of

tables; the value of cos(90°-0): tan(180°-4)

Section B

9.

In the figure, AB is u diameter of the circle, C is a point. on the circumference CX LA

་་་ a)Show that CX= =AX XB: (b)If AB-9cm, AX=aen,

express the area of square of side CX 11 turus of a. (c)Find the maxi

of the square of side

1.0

CX.

area

A horizontal circular ring of radius 30em is suspended from a: point 0 by three chains OA, OB, OC each 50cm long, attached, to equally spaced points A, B, C on the ring (a)Find the angle, of a

chain makes with the horizontal.

(b)Find the depth of the

ring below 0.

(c)Find the angle between

two chains.

11

(ie from...

pratigre-ren to

colourless)

→ CH; BrCHI_Br 2-dibromeethane

Carbon dioxide, turns limewater milky Because of the formation of the insoluble white. calcium carboute Ca(OH)2+C0,

CaCO3(3)+U2(

However, excess carbon dioxide turns the resulting mixture colourless again because it converts. calcium carbonate into soluble calcium hydrogen carbonote.

Cat!!C0;}z

Carbon dioxide does not support combustion so it cau extinguish a burning substance. However, When a magnesium is burning gives

aut

a large amount of heat; the heat thus produced

decomposes carbon dioxide, liberating the oxygen in which it cau continue to burn,

the centre of the. circle, and Pisa point outside the circle, PA and PB touch the circle at a and B respectively, AD produced meets the circle at 97. Prove" tiche pu

(a)1, B, C and A ar

ACHD. are

0.

In the figure, AB is an are of a circle

varius r, WA, OB, TỪ

Gare taurents at A, 1} and R respectively. 2000-90% 10=2cm,"

(0) 1, (a)Pind. Po in terns of (b)Hence or otherwise,

find the value of r

--27 and

15%

(a)Given that

2m 5n, find n and zi. (b)Solve the equation.

14.A bag contains three.

kinds of coins. If ther ražio of the runters of 50¢ coins to 20¢. cains to 10¢ coins is 3:2:1 and the total value of the coins fa

the tota} $20, find number of coins.

15.

The figure shows the sketch of the graph

2

y=n~(x+m)** which

posacs through the points (0, -3), (1, 0). and (P) (0)

(a)Find the values of mi,

n and p.

(b)Pind the greatest

value of y