真二筆張四第日四十月四年巴塞 WAH KIU YAT PO
報日橘茶
四期星日九廿月五年九六九一番公年八十五國民中
曹教僑電
英中會考數學(三)試題
戳 僑 華
英中會考化學科答案
·王錦釗。
1... fortificat
of Education. Eras
Suggested Answers
Chemistry (Section B)
(English)
SOLUTIONS
(a)
Observation
Test
1. II
Two colourless.
Orystalline solids
2. XY:
which do not
react with each
other in the dry state.
White ppt. format dissolved which dissolves on in cold
boiling. On cool- water & ing the hot- their
solution, colour- solutionless needle-shaped
mized:
crystals appear,
3. X heated Some brown gas
with
cono.
12304
4. 1 +
copper
turnings. heated with
conci
82504
5. KS
passed into
: an aquSOULS
solution
of X
given out.
Dense brown fumes. given off.
Inference
N12
X and Y contain Pb" ions and C1" 1ons, Since the ppt, formed is lead chloride PbC1. Lead chloride 18 the only substance which is soluble in hot water and which re-crystallines on cooling, forming. white Bilky heedles.
for agai
Pb ♦ 201→→ Pb012
X 18 probably a Bitrate, 1.0. Xt probably lead nitrats Pb(NO2). It cannot be lead chloride for lead chloride: im insoluble in cold- water.
Pb(NO3)2 + 2H2504
-
Pb(H)2 + 2HNO3
The brown gas obtained
being No, because some of the nitrio
acid formed decompoBUR
4HNO32H20 ANO2
+
02
I confirmed to be a
nitrate Cur 2N02
+ 4H*→→→Cu** + 2NO2 I
2620
|Black ppt produced
a lead salt.
Fb
+ 2H
(HAS)
PbS!
+ 2H*
lead sulphide (black)
X 18 lead nitrate, PO(NO
or ionion)
3F**
NO
NO + 2820
(iii) When cross ammonium hydrofids is added to ferric chloride solution, the ferric ions are precipitated as ferric hydroxide j FOCL + 3NE OK - Fe(OH) 3 √ + 3NH C1
(iv) When the clean, dry precipitate of ferrio
hydroxide is beated to redness until the weight is constant, the Tonidus is ferrio. oxide.
2Fe(OH)
3820
ferric oxide
Thus all the iron originally in the sample containing carbon as an impurity is finally converted completely into ferrio oxide.
Molecular weight of Fo
56 x 2 + 16 x 3ƒ 11248- 160
Wt, of iron reqd. to form 160 gm. Fe0.
112 goa,
Wt, of iron reqa, to form 5 g. 23
■ (112 x 6) gms. 3.5 gms.
160
Wt. of impura sample of iron - 4:0 gm Percentage of iron in original sample
2.5
* 100%
87.5%
(b) (1) Put some mulle ammonium ontorius into a
flask fitted with a rubber stopper, through which passes a thistle funnel and a delivery tube. To the free end of the delivery in connected to a retort as shown in the diagram. The back of the retort dips into some water contained in a beaker, Some concentrated sulphuric acid is poured down, the funnel, and the mixture is heated. The gaa evolved is hydrogen chloride which dissolves in the water forming hydrochloric acid. If the gas is passed for a long time into the water, a reasonably concentrated solution of hydrogen chloride will be obtained.
E80 * KH 01 MF To + HCL f*
hydrogen chloride
retort
NE CI &
cone.
MATHEMATICS Syllabus A
PAPER-IN
GEOMETRY
Time allowed-Two hours
Attemp: ALL questions in Section A and any FOUR questions in Section B.
SECTION A (40 marks)
Candidate Ne
Credit will only be given for the correct answer. For questions 1-3, put ■" in the box opposite to ins correct answer, and for questions 4-8 put the answer in the space provided on the question paper. The question paper that be handed in. Any working, may be done on the last few pages of the answer book bus will not be marked, Questions 9 and 10 should be done at the beginning of your answer book.
1." (2 marks)
Which one of the following expressioni is equal to the sum of the marked angitt is i
( 2 x 53*
(b) 3 x 90°
jol
4 X 90°
fe
6 x 90°
2.
(2 merks)
Fight
00000
ABCD is a trapezium with AD//CD and AECCD. ?, 2 are the mid-points of AD and BD rempactively Which one of the following Statcavorits must be true?
[} • MN = √ DC
(b) MN = (AB + DC)
(c)
MN » DC + 1⁄2 (DC ~ AB)
(a) MN (AD + BC)
(0) AB: MN = MN : DL
3.
{Ima
00000
Which one of the fullowing sets of dan will not necessarily imply that the triangles ABC and XYZ ah. congrient?
(a) AB - XY,
(b)- AB = XY,
{c}· · AB = XY,
BC=YZ,
AC - XZ
BC= YZ,
LB = LY
LA - LX,
23 - 24
(d) AB = XY,
LA = EX = 90°,
BC - YZ
{e}_{AB = XY;=¿B = ¿Y,
AC - XZ,.
*
(4 Maria
The diagonals of a thombus are respectively 16 cm and 26 cm. Find the ares of the rhombu
Fig
6. Plane
test
carried
out with
clid Y
Lilac colour
Y a potassium salt
Y is potassium chloride, XC1
(Both lead nitrate and potassium chloride are
colourless crystalline solide, which are soluble in water and whose solutions react to give a white
opt. of PbCl2 as represented by the equation:
2K01 - Pbc12
ZKNO3).
(b) (i) Action of micrine on hydrogen sulphide gasi
Cl2 + H2S 2001
8
(11) Action of chlorine on sulphurous acid
C12 120 + H2S03 2нсь +
B2SOA
(iii) Action of chlorine on ammonia gas
3012+ BNH3
6NH4C1 ✦ Na
These are OXIDATION reactions,
3. (a) (1) Iron reacts with dilute hydrochloric acid
to form solution of ferrous chloride There is no reaction between carbon and hydrochloric acid.
Pe+ 2H01 ·
FeCl2
*
↑
heat gently
En figure 2, straight line FAG toraches the circle at A. DE is paralle! to FG. ¿CBA » 72°. Calculate LEDA.
(4 marks)
solution of.
hydrogen
chloride
in water
WLWCL
All and DC are two chords of a circle. When produced they mest at E. HAB = 4 inches, BE-6 inches, and CE-3 inches, calculate the length of CD.
7,
(4 marks,
Answer...................
•Inches
Trimgles T1, T's and T, are all similar to one another. The rate of the lengths of a pair of corresponding medians in T and T2 is 3: 4. The satis of the lengths of a pale of corresponding Trigida in Ta and Fa in 8:10. Find the ratio of the areas of triangles T, and T.
...
(ii) Mix some solid potassium nitrate with some solid ammonium chloride, and place the mixture in a round-bottomed flask. When the mixture is gently heated, a gas, nitrous oride, is evolved. As the gas is fairly soluble in cold water, it is collected over hot water.
#
(6 marks)
KNO3
NEC1
KC1+ N20 ↑
+
2#2
ferrous chloride
(in solution)
"arrous okloride is oxidised by nitric
id forming ferrio chloride.
-Cl2 + 38C1+ HNO3 - 3F.Ciz
ferrio
chloride
BRACL
+ Nof+ 2820
(in solution)
heat
gentl,
nitrous oxide
B
Area of T
Answer:
Area of T
D
Fig. 3
In figure 3. ZBAČ • 90′′, AĊ = 3 inches, AB = 4 inches. AE is the angle bisector of 190 AD is perpendicular to BC, Calculate the length of (1) EC (ü}DC (M) ED.
Ai trous
oxide
9.
(6 muki)
water
Tomorrow, we shall look into questions 5 and 6,
EC-
Answer: DC-
ED
inches
itches
inches
Given the above line segment of length p Inches and using compasses and ruler only, construct a line segment, AB squal in length in √18 p. Measure the length of AB in inches. (No descriptium is required; but all construction lines brust ba clearly shown)
10.
(6 muki)
With ruler and compasses only, construct a regular hexagon ABCDEF of side 17 Inches. On AỜ construct a rectangle ACXY equal in arcs to the hexagon. Mieasure CX. (No description is required; bus all construction lines must be clearly shown).
SECTION 1 (60) marks).
CAUSEE)