8+=A=#BTRJ
真二第張五第
1977中學會考試題預習專欄。
明德社主編
化學(廿六) ·朱宏林·
Chemistry (26)
Answer to 0.42
A.
a) The black substance is correr
(II)oxide.
b) as X is composed of nitrogen
and oxygen.
c) It is because some of the cop-
per powder have combined with oxygen to form the oxide.
d) ass of nitrogen is
28
x
50
mole 24000 moles
= 0.0583 &
e) Kass of oxygen is
(25.067-25.000) g
= 0.067 &
mass of 100 cm3
of cas X maas of 11+mass of 0
(0.0583 + 0.067) s
0.1253 8
g
Molecular mass of gas X is
24000
0.1253 x
30
no.of moles ño. of moles of nitrogen of oxyreni
0.0583
=
0.067 16
14
= 0.00417: 0.00419
=1:1
the empirical formula of gas X is NO,
h) Let the molecular formula of
gas X be (10)
Then, molecolar mass of gas X
= (14 + 16) x n
= 30.
Hence, n = 1
Therefore, the molecular
mula of gas: X is NO.
i) 20u + NO →→ 2000 + N2
3) Brown fumes of nitrogen diox-
B.
ide are observed.
2+2NO 2
a) When chlorine gas is passed
into hot, concentrated KOH, it reacts with KOH to give pota- ssium chlorate, potassium chloride and water.
3C1+6KCF5XC1+KC102+3]10.
A redox reaction takes place.
The purple potassium permang anate solution is decolourised, Hydrogen peroxide
re using agent,
2
1.
450 to as the
2+
2
2n +
8H20 + 502
So effervescence takes place rs oxygen has been liberated.
Answer to £. 43
a) 21202
2250 + 32
b) from the graph, it is found
that the maximun,volume of oxygen is 240 cm.
c) About 8 minutes bed clapsed
when the reaction is complete. No. of molec of oxygen ir
240 0.01 moles 24000.cm
e) according to the equation
211202
21120+02
No. of moles of H202
2 x no. of moles Ca
= 2 x 0.01 moles
0.02 moles
Since there are 0.02 moles of hydrogen peroxide, in 50 cm
of the solution of H20;
or,
concentration of HD is
0.02 moles x 1000 cm3
50 en
= 0.4 moles dn
-3
= 0.4 roles dm3 x 34 g-mole
13.6 g dm
f) After 4 minutes, 220 cm3 of
oxygen is collected, therefore the fraction of 22 decomp.
osed is
220
ན
11
22
240 cm c) The speed is the fast at the
start because at that time the Concentration of hydrogen per oxide is the greatest.
a) The reaction is exothermic as
A is negative,
b) No. of moles of annonia in
51 g of armonia. is
51
- 3 moles
17 c
According to the riven equet-
WAH KIU YAT PO
ion, 186 kJ are evolved when 2 moles of armonia is formed; the heat charige for produc-
ing 3 moles of armonia is,.
186 kJ x-2 = 279 kJ
the field of armonia is incransed;
ii) the yield of armonia is
decreased;
iii) the yield of ammonia is
increased.
a) The c talyst usually used is
finely divided iron.
e) The catalyst has no effect on
the equilibrium position but it can speed up the attainment of the chemical equilibrium. f) According to the equation
\\\2(c) + 3H2(6) - 2N
3 vols
21 (8)
2 vola vol. of ammonia obtained is,
150.cm
100 cm
Answer to C244
RaOH + HCl
Naci +
Na, CO2+211C12ac1+0+00 b) Let the mass of Naol in the
mixture be n g,
Then the mass of Na,CO in the
mixture be (4.12 - m) 6.
Ho. of moles of NaOH in the 25
am of solution is,
25
-moles x
moles
3
48
400 And, no. of moles of NaCO in the 25 cm of solution is,
(4.12-n)
106.
25
moles
According to the equations in (a), no. of moles of HCl requ ired to react with 25 cm:
of the solution
no, of moles of Fa
1.12 — my
2 z no. of moles of NaCO3
+ 2 x
oles 100
1060: Pit, the actual amount of ICI red to react with 25 cm of the solution of the mixture in,
18
x 0.5 moles 21000 0.009 roles Therefore, we have
(400
m
+
=2
4.12
530
= 0.009
Hence, the mass of NaOH is 2.g. and that of Na, CO, is 2.12.6
6 of NaCH in the mixture is
2 4.12 112 x 100%
1
48.54%.
and for la,CO2 is 51.16%
Carbon dioxide, oxyren and fluorine oxide because their b.pls are well below the room temperature.
b) Dinitrogen tetroxide (110); because its b.p. is near the room temperature. Carbon dioxide (CO); because its b.p. is lower than its J. P.
d) Lithium oxide, Li,C: because
it has a very high m.p. and b.p. and it can conduct elect- ricity even in molten state, Beryllium oxide and boron ox- ide; becge they though have hich .p.'s and b.p.'s yet they do not conduct electri city in molten state. f)i) lithium oxide
foto
ii) fluorine oxide
E
Answer to 45
A.
報日僑華
e) no. of moles of
2-
SO A
ions
=no. of moles of metallic
sulphates
0.0006 moles
there are 1 mole of 50 2-
in 1 mole of metallic sulph- ate.
Hence, the ionic charge on the metallic ions is +2 because
1 mole of metallic sulphate consist of 1 mole of metallic ions and 1 mole of sulphate dons.
The possible formula is MSO
4. where denotes the metal. c) Let y be the relative mass of the metal M, then the formula mass of the metallic sulphate
119 is, (y+32 + 16 x 4)
y= 119 - 32 - 64
- 23
is iron(II) chloride; A is atean.
a)
b) Te + 2001 - Fecl2
+ H2
c) It is because iron(II)chloride
is easy to sublime so it cannot be collected at the hot part
e) No. of moles of HC1 in 56 cm
is
56
24000
moles zo moles According to the equation in
no. of moles of FeCl
x no. of moles of 501 ·· - 1 x 10 roles
六期星 日七月五年七七九一公年六十六國民薪中 育教僑额:
AH is a diameter OF circle-ABHK
6.
Da
in the Figure, if the are
area of AADK AAKB and ABKC are 2, 3 and 4 sq. units respectively, thex area of CKD is
A. 5 sq.units
B.. 3 sq.units
c. 6 sq.units.
D.
23 sq.units.
cannot be determine.
囚
14. 1 loga + logblog (
a+b), the value of a
in terms of bis
b
Av.
C. b-1
b+1
t..
·b
b
15. The values of x in
sin(2x+30)=cos(x−30)°,
is/are
(1) 0 (2) 10
(4) 150
(3) 30
What of the following
is true?
A. (1) only
B. (2) and (3) only c. (3) and (4) only
D. (1) and (3) only E. (2) and (4) only
16. Which of the following
81°x 9 is equal to
+9
7. If a, b, c,
mass of iron(II)chloride is, x: 127 €
d are integers and none of them is zero, which of the following
A..
C.
expressions can be
E. 10
equal to zero?
1.59 G
a) 0:0 +
Cu +
數學(廿六)·女長波·
Mathematics 26
Exercise 12
Multiple choice questions.
1. The area of a cond is
16sq.m. By what area is
represented on a map of scale 2cm to 1m? A. 64sq.cm C. 165q.ca
E. 454.com®
B.
32sq.cm
D. 8sq.cm
A train 200m long Dasses
through a tunnel 1000m
long at a uniform speed of 20m per second. How many seconds does it take the train to pass the tunnel completely? A. 30
B. 40 D. 60.
C. 50
B. 70
3. If it is required to
construct a triangle ABC such that B=30°, b12
c=10, then
A. there will be no
solution,
B. there will be two
solutions
C. There will be only one
solution, which is ä right-angled triangle. D. there will be only one
solution, which is an obtuse-angled triangle there will be only. one solution, which is an acute-angled, tri- angle.
(x-5)(x+1)>0 is equivalent
to
A. 54x=-1
B. X = -1 or x = 5.
C. X- or 5x
D. -5 x 1
1-1x5
5 hich one of the following
following sketches is
the graph of
y =
sin
A.
EO
a) Ba2+(aq) +0,2-(ng) →→→→RaSO4(s)
b) No. of moles of metallic sul-
phate is
30
x 0.2 molés. 1000
0.0006 moles
c) From the graph, it is asen
that the volume of barium chloride solution is 6 cm.
d) According to the equation in (a) for the precipitation, no, of moles of sulphate ions =no. of moles of BaCl2
=
G
0.1 moles
1000
0.0006 males
C.
Xo?
ד
(1) a+b+c+d·
· (2) a2 + b2 + c2 +
(3) a3+b3+c
(4) 4
a+b+c
A. (1) only
B. (2) and (4) only
C. (1) and (3) only
D.
only
E all of them.
If sinx = -1 where 0° <x
360°, then x =
A. 0° only B. 90° only C. 180° only D. 270° only. I. 0 or 1800
in the figure, ABC is a semi-circle, BELAC, AD= 6; DC 2, BD A. 13
10. 300 cons of food last
2400 soldiers For 72 days, for how many days would 200 tons of food last 1800 soldiers?
A. 81 days C. 144 days
B. 36 days
D. 162 days
13
F. 64 days. IF x2+y2=88 (x+y)?
and xy=7, then
A. 14 C.22
49
B. 16
30
12. Aman goes downstream in his motor boat for a distance of 3km and at once returns to his starting point. How did it take him to make the entire trip?
(1) with the stream
flowing at 1km der hr, he traveled downstream at the ̈ rate of 10km per hr. (2) His average rate for
the entire trip was 30 km der hr.
A. The problem can be
solved using only the given information marked (1)
B. This problem can, be
solved using only the given information marked (2)
C. This problem can be
solved only by using the given information marked (1) and (2) D. This problem can be solved using either the given informa tion marked (1) or (2) F. This problem cannot
be solved with the given information
13. in the Figure, if BC is
a diameter of the circle A3C, which of the Following must not be truc?
B. 0.1
17. In the figure, the
circles, touch internally at C and AB is the tangent to the smaller circle. 1F LAPQ=30° then LBPR is equal to A. 30° B. 459
C. 40°
D. 50°
1.none of these.
18. If xasine, y-bcose,
then the relation between x and y is.
A. b
B.
C.
2
D..
ab
Given two numbers, one even and one odd, their H.C.F.
(1) must be oad.
(2) must be even
(3) may be odd or even. Their L.C.R.
(4) must be odd.
(5) must be even
(6) may be odd or ever Which of the following. is true?
A. (2) and (5)
5. (1) and (6)
(1) and (5)
(3) and (4)
. (2) and (4)
20. A, B, C. subscribe a
$3800, $5700 and $7600) respectively for run- ning a business. The profit after one year is 32700, according to the ratio of capital. A shall share
A. 35000 8. $550
20. A, B, C subscribeo 33800
35700 and $7600 res Dectively for running
a business. The profit after one year is $2700, according to the ratio of capital. A shall share
A. $500 C. $600 L. 3700
B. $550
D. 3660
Answer:
1 A 2 D 3 D
6 D
11 C
16 B
7.,C
12 B
17 A
8 D
13 F
18 A
4 C
9.Е
14.A
19
5 E · 10 E
15 C
20 C
Alsif caña
Answer:
A. ABLCK
1 E 6 B
11 B
16 D
3. ZHAK + 4BXH = 90° C. ACHK and ACAB are
similar
2 A
7 D
12 D
17.C
C
8 B
13 C
18 D
A
9 E
14 A
19 E
A 10 D
15 D
.20 A
D. 3K is a diameter of
circle ABH K
VAWN.
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