1967
X-XX..
日八廿月十年未丁屋夏
WAH KIU YAT PO
CITY
D&英文中學會考試題預習專欄
1968,英文中學會考試題預習專欄
3. (a)
物理科 (五)
陸永耀
化學科
(五)
王錦釗。
Chemistry (5)}
Physics (5%)
Cuo
olution
Factors governing the pressure at any point"in) 2 li-wide-
63.5+16 *79.5
163.5
1. Fressure in a disula increases with depth
(pk)
2. Liouid bressure 19 proportional to density
(poca)
(b) 43 cm-diameter glass tube is climped vertically over a lar e beaker, .. flat thin metal pist attached by a thread to a spring palance is held tightly to the lower end of the tube. water is poured gently into the tube after the spring Lalance is clamped to a suitable position, It will start leaking when the downward thrust P- Wy
here R is the spring-balance.
reading
WW is the weight of metal
plate
IF is the downward thrust
which equals to the product of pressure. and are
The depth, h cm, of water column is then noted..
The experiment is repeated for several times, with Farid h recorded. If pressure is/ proportional to depth,
constant..
When 79.5 gms, or cupric oxide:13 reduced, in afstream
of hydrogen.
Loss of weight (79.5-63.5) gms.
16 gms.
Now weight of mixture of cupric oxide and copper) - 5 gms.
Weight after reduction
4.2 gms.
Loss of weight (54.2) .
0.8 gm. Thus weight of cupric oxide in Eng original mixturej
(79.5 x )ems.
16
3.975
9.
per in the origina 1}
1.e, weight of uncombined
mixture (5 3.
- 1.025
Hence percentage of
ixture
E
1.025 5 20.5%
copper in the original
2. Volume of oxygen given of at 16°C, and 765 mm. ag
* 343.25 0.0.9407
Volume that the gas would occupy at N.T.P."
765 760
XX 343.25).0.0..
273
289/
日九十月一十年七六九一膺公年六十五國民中
N=CO2101120,
23x2+12+16x3+10(2+16)
106 180
296,
101 20
10(2+16)
180)
When washing soda crystals are heated, they will lose all their water of crystallisation.1The residue is anhydrous sodium carbonate,
Loss of weight when 286 gms.” of washing soda? crystals are heated - 180 gua.
Kence loss of weight when 2.86 gms (of washing soda) crystals are heated 1.80 gms./
(b) 2X0103
2(39+35.5+16x3}
245 gue.
+
--201p+302 ↑
13x32
- 96
When potassium chlorate is heated gently with aj catalyst, such as manganese dioxide, it will decompose completely and give off all of its oxygen. The residue is potassium chloride,
Loss of weight when 245 gus "of potassium chlorate are heated 96 gms.
"Loss of "weight"when 12.25 gas Tof potassium
12.27 hlorate are heated - ( x 96) gm9,
245
4.8 gms.
(c)
CaCO3 40+12+16x3 -100
12 + 32
(C) Hydraulic Press
Pascal's Principal pressure is transind? ted equally throughout the whole of ar enclosed fluid is employed in this mechane. Its simplest form consists of a cylinder and piston of large diameter (A), connected by a pipe to a force pump of much smaller diameter (a). A small force (f) is applied on the smaller piston (a). This produces a pressure (p=
on the enclosed fluid and the same pressure is transmitted by the fluid to act on the under side of the larger piston (A), A resultant force (F p), much larger than f, enables the machine to support a large weight
7- A
(a).
HONG
= 319.0.0.
0.319 litre
2Pb3046b0
2(207 x 5 + 16 x.
When the mixture of red lead and litharge is heated, the red lead is decomposed qesyleiding oxygen) and litharge. Litharge does not unders chem decomposition on being heated,
Weight of oxygen obtained from 1370 gms.
* 32 gma...
Volume of oxygen obtained from 1370 gms. lead = 22.4 litres at N.T.P..
Hence weight of red Lead required to yield 0.319 Litre of
of Os at N.T.F..
0.319
32.4
19.51 gms.
dinal weight of red lead and Litharge Percentage of red lead in the
100% - 78.05
red
When calcium carbonate is heated strongly, it will decompose giving off carbon dioxide. The residue is quicklime or calcium oxide. Loss of weight when 100 gus."of calcium carbonate are heated like gone.
Loss of weight when 1,00 gm of calcium Icarbonate are heated = 0,lili go.
Questions for next week (6)
Salts may be prepared by (a) neutralisation of an acid and an alkali, (b) double decomposition, (e) direct synthesis, Illustrate these three methods by describing, with experimental details, thay preparation of (1) pure, dry crystals of potassium nitrate; (ii) pure, dry calcium sulphate,(111) anhydrous ferric chloride,
Why is it that solutions of salts are frequently
either acid or alkaline to litmus? Illustrate your answer with examples.
State the assumptions made in Dalton's Atomia Theory State thras laws of Chemical Combination,
Two oxides A and B of • certain metal were hested Ln current of hydrogen and the water in each case was weighed. The following results were obtained:
1.975 gms, of A gave 0.45 gm of water; (b) 1.42 gms, of B gave 0,18 gm, of water, Show that these figures illustrate one of the Lawa of
hemical.combination..
BRARES.
Spectively)
Let angle COA*- angle CAB - Since angle OAC.
Cile:10sine
10 x 13
Ans, In the thinner limb mercury level falls
4.84 cm, while in the fatter limb it rises 0.33 cm
If three forces, acting at a point equilibrium, they can be represented in magnitude and direction by the three sides of
triangle taken in ordez.
XON
If the force acting at a point are in equilibrium the sum of their components in any given direction že zero,
(by ine umown weight a 15 nung el one mla-Day 1-
between P and Q Equilibrium is maintained whom the string is depressed to and inclines at an angle ✪ with the horizontal. By the equation) of equilibrium
120
be the difference in levels, and
fall in the thinner linky
rise in thicker limb
water column
hỵ • hɔ = x
fince and B are on the same level
Pressure at a - Pressure at Biel
13.6(h
hd xD (d: density of waterf
density of mercury) h= (hi + hg) I
~~(2)
Volume of mercury suppressed in thinner linh equal to volume of mercury rises in thicker 1.
Where a and w;r and are the areas, and radius
of the two limbs respectively
Since
hj - léh2
From equations (1) and (2)
13.6 in
70
70
17 x 13 0.33
16 x 70
x 13.6
2T sine
- 2 W sino
-E
W the tension in a light string is the same throughout the string, and is unaffected by the's tring passing over smcot' pulleys)
If W is known and is measured the unknown weight X is determined.
(c) Let AB represent the rod, 0 the point or
suspension and G the centre of gravity of the rod.
Since there are only three forces acting on the rod, the lines of action of them must through 0.
Singe
1225 - 132
angle AuB GO
-GAGB
90 and}
By triangle of force, the three forces T2 (tensions of the strings) and W are represented both in magnitude and direction by the sides CA. AD and OC of triangle CAO
Ans. The rod inclines at 6
with the vertical.
13.22.6
The tensions in the strings are [84_and] .9.23 lb.wt."
Questions for the next week
(a) What is meant by centre of gravity
(b) Explain the terms stab or
neutral equilibrium.
unstable, and!
(c) Explain how you would Locate the C.G.for as
rigid rod which may not be of uniform density. (d) A sheet of paper is in the shape of a rectangle
9 in. x 12 in.; one of the shorter sides 197 folded down, so as to lie entirely along one of the longer sides. Find the position or the centre of gravity of the whole sheet thur folded.
10. (1) Under what conditions does a body accelerate;
What factors determine the acceleration? (b) Distinguish between potential energy and
kinetic energy. Describe the changes that occur during the fall of a body which falla freely from rest,
(a) A raindrop weighing 10 milligrams falls from a height of 1,000 metres. Calculate, (a) its velocity, (b) its kinetic energy on reaching the ground assuming that it falls in a vacuum. (g - 981 cm./sec,^.)
Explain why these values do not give the actuall results for a drop falling through the air.