買四第張五第日八廿月正年巳丁屋夏
1977中學會考試題預習專機
明德社
化學(十九) ·朱宏林·
Chemistry (19)
Question 32.
In the experiment as illustrated below, a mixture of concentrated sulphuric acid and potassium ní- trate crystals is heated gently in the apparatus G and a pale- yellow liquid L is collected in the receiver
conc
KNO,
G
Goed by tap water.
brown fumes
water
heat
ceiver
pale-yellow. liquid L
a) Give the name of the appara
tus G.
b) What is the pale yellow liqu-
id "L?
c) Give the equation for the re-
action which takes place in
G to produce the liquid 1 which has distilled over. d) Liquid L and concentrated sul-
phuric acid are both liquids. Why does liquid L only distil off and hot sulphuric acid? Liquid L is expected to have no colour; explain why it is pale yellow in colour.
f) Suggest two simple ways to
remove the yellow coloration from the liquid L.
g) Why is the apparatus G heated
gently in the experiment? h) Why has the receiver to be
cooled by the tap water?
1) It is found that in this 'exp-
eriment the whole apparatus is made of glass. Why is this so?
3) Describe briefly what would
you observe and explain what happens, giving equations, in each of the following cages:- (1) An excess of liquid Lis added on to a few copper tur- nings in a test-tube; when the reaction is over, te re- action mixture is heated. strongly.
(2) Some sulphur powder is warmed with an excess of liq- uld L, with a few drops of bromine as the catalyst. The reaction mixture is then fil- tered and to the filtrate a few drops of barium chloride solution and dilute hydrochl- oric acid aro added. Question 33.
A.
The diagram below shows a simple method by which a sweet-smelling liquid, ethyl propanoate, is ob- tained in the laboratory..
heat
thermometer
mixture and cono
H2SO4
receiver
liquid P
Write down the structur 1 for- ula of ethyl propanoate.
b) What compounds are present in
the mixture i which on heating
with a litlle concentrated sulphuric acid gives the pro- duct, ethyl paopanoate?
o) What are the two functions of concentrated sulphuric acid in this experiment?
d) Why is the receiver immersed
in the cold water?
B.
WAH KIU YAT PO
Can concentrated hydrochloric acid be used instead of conc- entrated sulphuric acid?
Give the equation for the for- mation of ethyl propanoate. What is the apparatus A called? Which of the two openings, X and I, is for water to enter- into the apparatus A?
What is apparatus, A used for? What would you obtain if some. of ethyl propanoate is boiled with aqueous sodium hydroxide. Wrtie down the equation for the reaction.
Describe your observations and explain what happens, giving, equ- ations, in each of the following experimenta:-
a) A mixture of concentrated sul- huric acid and copper trunings in a test-tube is heated and a moist potassium dichromate pa- per is placed aross the mouth of the test-tube."
b) A mixture of propan-1-ol and
acidified potassium dichromate solution is boiled under reflux for a long time..
c) Aqueous ammonia is added slowly into aqueous copper(II) sulphate until an
excess of ammonia solution has been addet.
Question 34
A. 2.44 g of barium chloride
crystals of formula BaCl,xH¤ ̧ are dissolved in water, the solution is added 25 of a solution of sulphuric acid containing 49 g of pure acid per litre, and the precipitate formed filtered, carefully wa- shed, and dried. The excess sulphuric acid,in the filtrate requires 25 cm of 0.2M sodium hydroxide solution for neutra- lisation.
a) What is the molarity of the
sulphuric acid?
b) Write down the equations for
the reactions involved? -
c) Determine the value of x,
the number of water of crya- tallization, in the sample of barium chloride.
Calculate the maximam mase of the precipitate that can be obtained.
B. The following diagram shows
the apparatus used to prepare an extremely poisonous gas C in the laboratory.
dilute hydrochloric acid
solid D
felt
marble chips
aqueous
sodium hydroxide
gas. C
water
Name the substances B, C and D respectively. b) What is the function of
placing the aqueous sodium hydroxide in the bottle? c) Write down the equations for the reactions in (1) the flask;
(ii) the combustion tube; (iii) the bottle containing
sodium hydroxide.
d) Can dilute sulphuric acid be used instead of dilute hydrochloric acid? Explain briefly your answer.
e) Describe briefly why the
gas C in fatal to mankind? f) What are the effects of gas
B and gas C separately on
(1) heated copper(II)oxide;
(ii) a burning magnesium,
報日僑華
Ametal wire (1 cora in
diameter carries » charge
At 90enul in hr and 15 mín.
Whet ** the current in the wire..
(n) A wire, 100m long and 2mm
四期星
in diameter has a resistivity
8 of 4.8 x 30
18 (i). What
ahm.m
the resistance
»
+1 the wire (15) A second wire nự the
same material has the sa973 IN weight as the 100-meter length grout twice its ameter What is the
tune".
(c) The following measure- ments of current and poten- tial difference were made on
a resistor
current (amnere)
Po fal
difference (volts)
0.5
2.18
1.0
4.36
8.72 17.44
Plot the potential differ- ence against current. Does it obey the Ohm's law? What is the resistance of the resistor, in ohms. 2 (a
de figure shown
12V 10
5.0.
12 valt battery of in-
John 1 ternal resistance 1 connected to an external re- sistance 5 ohms. If point. is grounded, find
(1) rate of conversion of internal energy to electrical energy within the battery. (ii) the rate of development of heat in the battery (iii) the rate of development of heat in the external re-
sistor.
[(b) As Nigure shown
5.2
3.0
日七十月三年七七九一腊公年六十六國民中
voltmeter v is applied to Açárcuit with a bettery,
a switch S, a resistor and an ammeter A. When the switch S is open, the voltmeter reads 1.52 volts. When the gwitch 5.
2
is closed, the voltmeter reads 1.37 volts and the ammeter reads 1.5 amp. Find the emf and the internal registance
of the cell. Neglect meter
corrections.
A 18 volt battery of inter- nal resistance is connected to A 5 ohm resistance and a 3ohm resistance. If point b is grounded
(i) What is the potential at.
point a ?
What value resistor must
e
inserted in the circuit at
to make the notential at a
7.5 volts ?
(iii) y battery has an intern-
I resistance of 1 ohm. What enf must it have to make
be 2 v} Us the motential at a when the battery is inserted.
? (the in the circuit at e resistor of part (15) is removed ).
物理
(+) 魯榮家
Kalin the figure below,
SENSIOS
Exercise 19
Plectricity
charge of an electron
-7.4
= 1.6 x 10
enutomb
(b) In the figure
potentiometer is a resist-
or with a movable tap. The 1
galvanometer has a resistance of 90 ohms, P has a regist- ance of 75 ohms. At what noint should the movable tap he placed if the current if the current in the galve name ter is to be 1/5 the current
ine be.
MODERK SEATHLMA (ICS (19)
Answer ALL the questions in
section A and any SIX in
section B. All necessary work.
ing must be shown clearly Section A
-5/45
1. if sinx..
Posx
the value of (sinx - cosx 2. As figure shown, two cir- cles of radii a and b are Louching each other at 2, JE PO is the common tangent of the circles, express the len-
terms of a and b, gth of PQ in
★教僑嘟
Induction that
2n
(b) g2n+1
+
1 is divisible by 8
2n+1
is divisible
Q
all: positive integers n
11. (a) Tf the nth term of a progressi
find tn is denoted by rín)
rth term of a G,P,
-
with T(1) · 1(3) T(S) 210. and T(2) *T(4) +
T(6)
420
(b) If the sum of the first
In terms of a
Sán) - nín +
find T(); and T{n},
12. (a) In the figure, ABCDEF
is a regular hexagon, Express
ar in terms of
† and ₫ where
FÉ
(b) Prove that if [B+) = 16−q!
then Tif.
13a. In the figure, 3. concent- ric circles of radii 4, 6 and 10cm respectively. A point is
marked at ran-
dom inside the
outer circle.
Find the proba-
(b)
that the
O
is in the shaded region
box contains 5 blue
yellow and 12 red marbles Three marbles are drawn one
after one. Find the chance. that (i) all marbles are blue,
no marble is ble (ii) the marbles are of
eo tour.
14
Marks
Frequency
10-19
20-24
4
10
-30-39
12
re
3. If the perimeter of a squa-
ABCD is equal meter, wî an equilateral trị- angle XYZ. Find the ratio of
their areas.
·40-49
26
50-59
41
to the peri-
50-69
70-79.
7:
80-84
5
290290
4. Find the range utk it the
equation x + 2kx
has no real roots.
5. Sketch the graph
(2x
(2y+
6. Solve the equation
(x + 1)
(x + 5) + fx
(x
81) = 0
The table shows the distribu-
30 Jon of 100 candidates in
7. Find the scalars my n such that គឺ mb + nê where
=
2f
=
+ 33 b-31 - 53 and 41 + 71.
|8. As figure shown, AOB is the
diameter of the circle, angle
43°.
|C PB = 15", angle CAB
find the value of x.
Section B
9. 11[f(x)}]2 = 2x^44-8(x2+1)
f
and f(x) is a quadratic ex-
pression. Find f(x)
10. Prove, by mathematicai
A thematics tes.
(4) Pilt in the table below
Marks less then frequency
9.5
19.5
29.5
༣༥;5
49.5
59.5
69.5
79.5
89,5
90.5
ii) Plot the cumulative fre- quency nnlvgen according to
(îñ ] If 45% of the candidates failed in the test estimate the pass mark of the test.
15. (a) Find the ratio of the (area of a square inscribed in
semicircie to the area of the square, inscribed in the eutire circle.
希望
(b) 'wo cylindrical containers are both full of the same li- quid. One has a base radius twice that of the itler, but is only one third of the other's height. If the small- er cylinder contains 61b feight of Liquid, what is the
weight of liquid in the larg-
er one?
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聞新港本
頁一第張六第日八廿月正年巳丁展室
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