真四第張五第日七十月二十年寅甲瑟夏 WAH KIU YAT PO
育教僑
17975-
中學會考專欄
化學科 十三 •陳湛杰
CHEMISTRY (#13).
Solutions for Chemistry (#12).
Multiple Choice Questions.
1. (a) 2. (a)·· 320)
Conventional Questions()
1. Panday's First Law of Electro- lysis the weights of substances formed at an electrode during. electmlysis are directly propor tional to the quantity of electri city that passes through the solu tion.
Faraday'a Second Law of Electro- lysis the weights of different elamente formed by the same quanti→ ty of electricity are proportional to the equivalent weight of each elementu
Volume of oxygen gas at 15°0 (273+15°K) and atmospheric pressure
mm Hg) a 11.7-0.04). (760
From ges equation PV/T = constat volume of oxygen at NEP conditions is
760 x 11.7 x 27 (273+15) * 760
= 11.09ca
Since 1 gm.-mole (or 32 mm. vb.) of oxygen occupies 22,414 c.c. at HIP, the weight of hydrogen 11ber ated is
** 11.09 x 323
22,414
001583.
For the same quantity of current weight of copper deposited is 0.062 gm. Therefore, according to Faraday's Second Law this weight must contain the same number of
equivalents an 0.01583 of oxygen. As equivalent weight of hydrogen is 1 and that for oxygen is 8, the equivalent weight of copper is
0.062
0.01533X8 31.33
2. The basic structure of the atom contains a positively charged nucleus surrounded by a äiffuses cloud of electrons, and that the number of electrons in the electrod cloud is equal to the number of positive charges (protons) in the nucleus. The number of positive chargea in the nucleus of an atom of a particular element is called the atomic munner of the element.
modern classification of the elements, known as the periodic system is closely related to the atomic structure. Thi: 103 or so y known elements are arranged in the Tord of a table designed to bring together in columns elementa that have similar chemical and physical Properties. The arrangement de
The
known es the periodic system, because many of the properties of elements are periodic functions of
their atomic numbers.
(a) Series (period) The horizontal IOWE in a typical periodic table are known as series, or periods. There is a total of seven such series. This hydrogen and helium constitute the first (the very short) series followed by a series of typical elements L, Be, B, C,
0, F and Ne.
(6) Group When the vertical ar rangements of the periodic table is considered, it is found that. they may be grouped into sixteen vertical columns or groups. These are labeled with Roman numerals. rum ning from LA to VIIA, VIII from IR to. VIIB and D Group contains the elements H, Li, Na, K, Rb, Cs and Fr whereas the me gases are grouped as Group 0,. including He,
ing He, Ne, Ar, Kr, Xe and Sub-group (0)
In Group T
I, the re are two subgroups, namely Group IA and Group IB. The former includes the alkali matale Li. Na, K, Rb, Ge and Fr. The latter includes the coinage metals Cu, Ag and Au. Sub- groups are also found for groups II to VII F
(d) Transition elementa These are clemente that have the same number .of alectrons in the outermost
shell but a progressively greater number of electrons in an inner 4 level. There are four auch. transition series, in which the additional electrons enter the 34, 48, 52, or Ed orbital, respectively (e) Typical elements. These are also known as the representative elements and ineludo the eight Familien of the and look elements (ie. TA, TIA, TI, VB, VIB, VIIB and C). (r) First Transition Semies includes
elements So, Ti, V, the Cry in, Fe, Co and Ni.
IVB
This
(z) Triada These ere groups of threa closely related elements: such as Ca Sz, Bai Li, Ne, Ki
Cl, Br, I. In these cases, it was found that the middle elements had atomic weights almost the arithoatical reah of the other two cloments. Moreover,
differ- ences between the atomic weighta of the three related elements waxu approximately constant
the
(h) Family Elements a group that show very similar physical and chanical properties are said to belong to the same fertly. The elementa, of, 475YU, IA, for sample make up the alkali-metal family.
Questions for Next Week.
The questions in this issue are related to 4.7. Structure and Bond- ings 4.8 states of Matter: 4.9% Energeticaj 4.10. Rate of reaction; 4.11. Equilibria. Study your notes ard
text
book before attempting the questions.
+ple Choice Questions Which of the following
compounde contain covalent bonda? 1.Ammonium
chloride 11.Sodium sulphate; III.
Sodium chlorido? TV.Chlorine:V.
Hydrogen chloride.
報日僑華
A. I,II,III only B. IV.only
C. V only D. IV and V only §. I, II, IV, V only
2. Blemmt. T has an atomic number 19. Using your knowledge of the periodic table, pradict the most pre bable compound that it will form with clement.U of storie, number 17.
B. 30 C. U2 DUTE. T
3. Which of the following reso biops are exothermic? L.Action of sir on red hot coke; II.Action of steam on red hot coke; III.Action of water on quickline:IV.Cxidation of ammonia to nitric oxide; V.Haber Process for manufacture of armonia.
A. I and II only 5. IV and V only C. I, II and III only D.VIII, IV and: V only E. A11. bxcept II
4. The following are characteristic of a catalyst: I.it. remains unchang luring a
a chemical reaction; II, it may accelerate or retard the rate of reaction III, it
ingy be dispersed homogeneously or heterogeneously; IV. it may initiate certain reactior that do not occur at room temperatu V. it functions by shifting the equilibrium position of reversible reactions
A. III only B. I,III only C. II,III only D.
1. I,II,III IV V III only
Conventioni Questions
Stata Je Chatellar's Primiple,th Show Low this principle can be used to predict the effecr of changes of temperaturo and pressure on the following systems: a.PC15FC13+0ligh b. CO+H,O=CQ_+H2¢©• N2 + 02=2NO;
| d. 250,+0=250,re.D&GO=CaO+CO2
2. Write an account of energy changi during chemical reactions. How can
a study of these, lead to a deeper. understanding of chemical reactionat
10975:
中學會考專欄
物理科 十三 • 陸永燫
PHYSICS (13)
Solution
Ta) The boiling point of a sub-
atance ia defined the temperature. at which its saturated vapour pressure equils to the external atmospheric pressure.
(b) The effect of pressure on
boxing - point.
A liquid boils when the s.v.pi 0E, the bubbleca éxcooda. the pressure outaide.. If the atmosphere%, pressure decreases, the liquid boils at a lower temperature, {s.v.p. temp. ).. Similarly. increased pressure raises the boiling point.
The effect of impurities on boiling point
The boiling-point of a liquid increases with the impurities present. When the mass of:
五期星
impurities is omill, the boiling- point is approxiliną toly proportion.
á to" amount of ass. (c)
boiling
(1) a volume
affact
quick process
at a definite temperature
(4) temperaturTE.
evevorstion
a surface effect
slow process.
at all temper ature"
tempem ture
kept constant may vary during boiling during evapo-
rating.
(a) Potential energy of 10kg of water at a height of 2m
➡ngh = 10 x 10 x 20 = 2KJ (1) If efficiency in 100%, Br
is all converted to electri cal energy.
Power generated - 2KW
(ii) If of it turns into us fu
work 1 of 2KW in wasted. The waste energy is, con vorted into heat in raising temperature of water by
༣་
mgh
=.mce
10 x 20
4200
2(a) Dew point is the temperature at which the air becomes saturatod With the wat
ter¬yapour present in. it.
15 vapour molecules in an en- closed space exert pressure on the wall of the container and the liquid surface. Some of theni re- enter and at the same time more molecules. go
into the space. A stage is reached when the rate of the number of molecules re-enter ing the liquid.enuals to that leaving • ́rnis avezny state is
17. known as dynamic squilibrium. The space is now saturated with vapour The pressure of vapour et this I stage is maximum, and is known as satumted vapour pressure (5.V«p.)
to distinguish with the unsatu
rated vapour pressure before the
dynamic equilibrium state,
... and volume
The pressure exerted by saturated Vapour is always constant for a
given temperature, even though the
vapour undergoes changes in volume
The part AB on
the graph.
describes tho.
effect of volume
changes on s.yard A. saturated
a.v.p. is kept
onstant. The
decrease in
volume causes
more vapour molecules to enter. the liquid per secord, but the number of molecules leaving per second remains constant, some vapour condenses. until dynamic equilibrium, is restored,
For unsaturated vapours, Boyle'a Law gave me the variation. 30.10 plotted according to Boyle's law; Pis in inverse proportion.
... and tempere fire 8.v.p increases with temperature. The temperature rise increases the kinetic energy of the molecules. More molecules escape and in- " creases the concentration in the
apsos. A new dynamic equilibrium is reached when the number of moleculen re-entering has in-
日七月二年五七九一年四十六國民萤中 有教僑華
orecsed. As a result, the number
of molecules in the space, at
dynamic equilibrium has increased.
The speed of vapour moleculos, and
thus, the pressure of vapour
becomes greater.
AB shows B.v.p. increases with temperature. There is no simple rule to govem for the variation 30. indicates the unsaturated vapour und ergosa
(c)
Vadour pressure
against Temperature,
(1) When water boils at 3590, the pressure has to been reduced to 42 mm F
(ii) At a pressure of 40 mm Hg, boiling point of water is 34°C (iii) s.v.p. at air temperature of 1590 is 12.8 mm Hg, (from graph) Dew point 100 Sv.P. dew point a 9.2 mm Hg
(from graph} Relative Humidity
Beyn. at dew point.
x 100% 9.2*
71.9%
x-100%
(iv) Room temperature 250 s.v.p. at room temp. 23.5 mm Hg
(from graph) Relative humidity - 90% a.v.p. at. dew point = 0.5 x 23.5
21,15 mm Hg Dew-point
22.5°C
(from graph).
(v) Dewpoint 5°0 s.v.p. at dew point 6.5 mm Hg
(from graph) Relative humidity = 75%- a.v.n. at room temp. 0.75.
=.8.67 Room temperature = 9°C
Questions for this week.
1. (a) M. and My are two plane
mirro:s placed in a room with dimensions chomi
himself from
(1) Can A person see
both mirror if he sits at po- sition A? Draw a cay-diagraŭ to support your, answer.
(11) If he sito at B, describe
the position,
2 the size, and
3.
the nature
of the images observed from mirrore M, and M, respectivel at position A.
(b) Three circular windows were made at the centre of a 20-cm cute as shown:
(i) Elace a rota-
tary plane mirror At the centre of: the cube, an obser- ver with his eye. position at the ziddle of window 1: caught the view outside the cube through window 2. What angle should the mirror rotate
such as to old
the maximum
of view through window 2?
(ii) Lens of focal lenght 20 on 19. fixed at window 3. An object, 0. is
placed at the cen-
tre of the cube. What is the nature
of the image seen by an observer
with his eye very close to the lens? Where is the image?
(iii) If a plane mirror in
put
5 cm in front of window, and the observer is kept at a distan ce from window 3, find the image position and its nature.
2. (a). In an experiment to find the focal length of a concave mir- rar, the object distance, u, and the image distance, v, were mea- sured and tabulated as follows- (cm) 30 40150 30 170;80:190 $100 (cm) 60 40 34 305 28 267 26. 25. From a suitable graph plotted, find the focal length of this. airror.
(b) Trabe the path of
(i) a ray which Bhikes a sheet of glass 80 r thick at an incident angle of 45°, measure the later al displacement. C = 1.5). (ii) ray striking one face of an equilateral glasa prism at a glancing angle of 30°, casure the deviation (M = 1.5)
(ii) a ray atiking one of the
shorter fases of a 45°-90°-45° glase prism normally. (iv) a ray striking normally at
the longer fiace of a right angled isosceles prism made of a material of refractive index 1.7.
冠金華大約紐
片笑大年賀
献盛 映大
娛最春肉性風香 樂佳節感感趣艷
天後
巨榮公歐 献譽司洲
演大春第
招施 笑
里維馬贏
作本
奧卡高
宜不童兒
角主「剛金七縱七擒七」
仙東加 福莫斯
作意
風題多養 趣材到眼 絕別無鏡 倫緻比頭
人上人天齊福艷
你程監變
THE ERFTIC MAN
色人意
無中生患
「布山卡」勁敵
妮拉伊琪珍 碧莎蓮納 法珍比。雅
豬養奧義,由大保感動色耳美祗艷但家人惜女男富原 超 飽證同作心仔女作福 福有天性 性人甲油 變雞眼觀身風又一當幻齊享嬌無傾仰全大 福眾受流起動前想天受妻事能心墓國王
合星派片春暨 演羣艶脫一
FILM
Page 20Page 21