中五化學/會考試題改編/短答題/四
1
S5 Chemistry Revision Exercise 4
1.
Cesium (Cs) is an element in Group I of the Periodic Table. Its relative atomic mass is larger than that of potassium.
(a) Cesium or potassium is a stronger reducing agent? Why?
Caesium.
Since caesium has a larger atomic size, it is
more readily to lose electron.
(b)
Write an equation for the reaction of cesium with water.
2Cs
2.
3.
+
2H2O
2CsOH
+
H2
Food can is made of iron coated with tin. Explain why it is not coated with zinc?
It is because zinc is toxic
27.53g of an oxide of metal X contains 24.96g X. What is the mole ratio of X to O in this oxide?
(Relative atomic masses:
mass of O = 2.57 g ,
5.
─→
O = 16.0，X = 207.0)
mole ratio of X to O = 24.96/207 : 2.57/16 = 3:4
What are the main gaseous products at cathode and anode in the electrolysis of concentrated sodium chloride solution
using carbon as electrodes?
Anode:
7.
chlorine ;
Cathode:
hydrogen
All members in a homologous series can be represented by the same __general formula___________________. They
have _similar___________chemical properties. Their boiling points __increase___as the relative molecular masses
increase.
8.
The atomic number of X is 12. An ionic compound XY2 will be formed when X is reacted with Y. Which group in the
Periodic Table does Y belong to?
Group VII
9.
Compound A
O
H
C
O
Compound B
H
H
C
C
H
H
H
H
H
H
O
C
C
C
H
H
O
H
(a)
Which one can turn wet blue litmus paper red?
Compound B
(b)
Which one has pleasant fruity smell?
Compound A
(c)
Which one has higher boiling point?
Compound B. The molecules in compound B are held together by
intermolecular hydrogen bond. The molecules in compound A are held together by weak Van der Waals’ forces.
中五化學/會考試題改編/短答題/四
10.
11.
2
What is the colour change when each of the following solutions is mixed with bromine water?
(a)
sodium iodide solution
brown
(b)
sodium sulphite solution
colourless
(c)
sodium hypochlorite solution
The following is the structural formula of a polymer:
CH3
CH3
C
C
H
H
Name the monomer of this polymer.
12.
n
But-2-ene
What are x, y and z ?
3Zn(s)
+
－
2NO3 (aq)
+ 8H+(aq)
x： aq
13.
brown (no change)

3Zn2+(x)
+
2NO(y)
+
4H2O(z)
y： g
z： l
The melting point and boiling point of X are 321℃ and 765℃ respectively. X can conduct electricity in molten state
without decomposition. What is the structure of X?
Giant metallic structure
14.
A sample of tap water becomes turbid after addition of potassium carbonate solution. What ion does the sample probably
contain?
Calcium ion
15.
－3
The density of a sample of concentrated sulphuric acid is 1.83 g cm
sample is 94.0% , what is the molarity of the sample? (R.A.M :
. If the percentage by mass of sulphuric acid in this
H=1.0，O=16.0，S=32.1)
mass of 1 dm3 (1000 cm3) sulphuric acid solution = 1.83 x 1000 = 1830 g
mass sulphuric acid in 1 dm3 sulphuric acid solution = 1830 x 94.0% = 1720.2 g
no. of mole of 1720.2 g sulphuric acid = 1720.2 / (2 + 32.1 + 16 x 4) = 17.5 mol
So 1 dm3 sulphuric acid solution contains 17.5 mole sulphuric acid, molarity of the sample = 17.5 / 1 = 17.5 M
17.
Is each of the following processes required a catalyst. If catalyst is required, give its name.
(a)
preparing ethyl ethanoate from ethanoic acid and ethanol
Yes. Concenterated sulphuric acid
(b)
converting sulphur trioxide to concentrated sulphuric acid
No
中五化學/會考試題改編/短答題/四
3
21.8g of zinc react with 250.0cm3 of 2.0M hydrochloric acid in an experiment. What volume of gas, measured at room
18.
temperature and pressure, will be evolved? (R.A.M.: Zn = 65.4；molar volume at room temp and pressure = 24.0dm3)
Zn
+ 2 HCl

ZnCl2
+
No. of mole of Zn =21.8 / 65.4 = 0.335mol;
H2
no. of mole of HCl = 2 x 0.25 = 0.5mol ;
No. of mole of H2 formed = 0.5 / 2 = 0.25mol.
vol. of H2 = 0.25 x 24 = 6.0dm 。
I.
III.
So Zn is in excess.
3
19.
methanol
II.
Sodium ethanoate
Ethyl ethanoate
IV.
propene
(a) Which of the above compounds has the highest boiling point? Explain your answer.
(II) sodium ethanoate. It
is because it is ionic compound while the other are substances with simple molecular structures. Ionic bond is
stronger than Van der Waals’ forces.
20.
(b)
Which of the above compounds can decolourize bromine in 1,1,1-trichloroethane?
(c)
Which of the above compounds has a pleasant fruity smell?
The catalysts in catalytic converter can convert :
(1)
(IV) propene
(III) Ethyl ethanoate
nitrogen monoxide to _____nitrogen________ (2)carbon
monoxide to __carbon dioxide___ (3) unburnt hydrocarbons to____water____and ___carbon dioxide__________.
21.
Name three compounds that can form a gaseous product when heated with ammonium chloride.
___Sodium hydroxide, potassium hydroxide , calcium hydroxide _______________________________________
22.
Calculate the oxidation number of N in each of the following compounds.
(a)
23.
NH3
-3
(b)
NO
+2
(c)
N2O
+1
(d)
N2
0
A student carried out an experiment by putting a piece of calcium in a beaker of water.
(a)
Will the piece of calcium sink or float?
(b)
Will the piece of calcium burn when it reacts with water?
(c)
What will be observed when a drop of phenolphthalein is added after the calcium has reacted with water? Explain.
The solution turns pink.
hydroxide is alkaline.
Sink
No
Calcium hydroxide will be formed after the reaction of calcium and water. Calcium
中五化學/會考試題改編/短答題/四
24. (a)
4
Which of the following polymers is / are formed by condensation polymerization?
O
1.
C
(CH2)4
O
H
C
N
Polymer 1
H
(CH2)6
N
n
COOCH3
CH2
2.
C
CH3
3.
(b)
n
F
F
C
C
F
F
n
Name all the above polymers.
1. nylon 6.6
2. Perspex
3. poly(tetrafluoroethene)
25. What pollutants can be removed from the following measures?
26.
(a)
installing scrubber
(b)
installing electrostatic precipitator
(a)
sulphur dioxide
particulates
What is the function of ammonium chloride in a zinc-carbon cell?
As as an electrolyte
(b)
What is the function of manganese(IV) oxide in a zinc-carbon cell?
As a reducing to remove hydrogen gas.
(c)
What is the polarity of the zinc case in a zinc-carbon cell?
Negative
27.
(1)
Sulphur dioxide can be prepared by heating copper fillings with concentrated sulphuric acid. Write an equation for
this reaction.
Cu
(2)
2 H2SO4

CuSO4
+
2 H2O
+
SO2
Sulphur dioxide can be absorbed by sodium hydroxide solution. Write an equation for this reaction.
SO2
28.
+
+
2 NaOH
 Na2SO3
+
H2O
Explain why concentrated sulphuric acid turns filter paper black.
It is a dehydrating agent that can remove the
element of water in the paper.
29.
Sulphur dioxide is better than chlorine in bleaching silk. Why?
30.
Adding slake lime to acidic soil can increase the production of crops. Why?
31.
Aluminium is more abundant than iron in the earth crust. However, human used iron earlier than aluminium. Why?
Aluminium is more reactive than iron.
Chlorine is too powerful that will destroy silk.
To neutralize the soil if it is too acidic.
It is more difficult to extract aluminium .