A compound contains 31.91% potassium, 28.93% chlorine and the rest oxygen. What is the chemical formula of the compound?
[K = 39, Cl = 35.5, O = 16]
คำตอบ
(D)
KClO3
2
The formula CH\(_2\)O for ethanoic acid is regarded as its
คำตอบ
(C)
Empirical formula
3
A little quantity of trichloromethane (b.pt 60\(^0\)C) was added to a large quantity of ethanol (b.pt 78\(^0\)C). The most probable boiling point of the resultant mixture is from
คำตอบ
(C)
82 oC – 84 oC
4
The chromatography separation of ink is based on the ability of the components to
คำตอบ
(D)
Move at different speeds in the column
5
In the reaction E+F ↔ G+H, the backward reaction is favoured if the concentration of
คำตอบ
(C)
E is reduced
6
What amount of mercury would be liberated if the same quantity of electricity that liberates 0.65g of zinc is applied?
คำตอบ
(A)
2.01g
7
Which of the following equations show that a reaction is in equilibrium?
คำตอบ
(D)
ΔG = O
8
PCl5(g) ↔ PCl3(g) + Cl2(g)
In the reaction above, a decrease in pressure will
คำตอบ
(B)
Increase the yield of PCl3
9
When H\(_2\)S is passed into a solution of iron (III) chloride, the solution turns
คำตอบ
(A)
Pale green
10
The Arrhenius equation expresses the relationship between the speed of a reaction and its
คำตอบ
(D)
Activation energy
11
When dissolved in water, NaOH flakes show
คำตอบ
(B)
An exothermic change
12
Cu\(_2\)S(s) + O\(_2\)(g) → 2CU(s) + SO\(_2\)(g)
What is the change in the oxidation number of copper in the reaction above?
คำตอบ
(A)
+1 to 0
13
The product of the electrolysis of dilute sodium hydroxide using platinum electrodes are
คำตอบ
(A)
Hydrogen and oxygen gases
14
The solubility of a salt of molar mass 101g at 20oC is 0.34 mol dm-3. If 3.40g of the salt is dissolved completely in 250cm3 of water in a beaker, the resulting solution is
คำตอบ
(C)
Unsaturated
15
Tetraoxosulphate (VI) acid burns the skin by
คำตอบ
(D)
Dehydration
16
When a salt loses its water of crystallization to the atmosphere on exposure, the process is said to be
คำตอบ
(A)
Efflorescence
17
Three drops of a 1.0 mol dm-3 solution of NaOH are added to 20 cm3 of a solution of pH 8.4. The pH of the resulting solution will?
คำตอบ
(C)
Greater than 8.4
18
25cm\(^3\) of a 0.2 mol dm\(^3\) solution of Na\(_2\)CO\(_3\) requires 20 cm\(^3\) of a solution of HCl for neutralization. The concentration of the HCl solution is
คำตอบ
(A)
0.5 mol dm3
19
The substance least considered as a source of environmental pollution is
คำตอบ
(C)
Silicate minerals
20
The furring of kettles is caused by the presence in the water of?
คำตอบ
(D)
Calcium trioxocarbonate (IV)
21
The property which makes alcohol soluble in water is the
คำตอบ
(B)
hydrogen bonding
22
Steam changes the colour of anhydrous cobalt (II) chloride from
คำตอบ
(A)
blue to pink
23
The gas that gives brown colouration in brown ring test is
คำตอบ
(A)
NO
24
Ethanol can easily be produced by
คำตอบ
(A)
fermentation of starch
25
Which of the following gives a precipitate when treated with NaOH solution?
คำตอบ
(A)
AlCl3
26
An example of element that can catenate is
คำตอบ
(D)
carbon
27
The reaction of an alkene with hydrogen in the presence of catalyst is
คำตอบ
(D)
an addition reaction
28
The number of isomers formed by C\(_6\)H\(_{14}\) is
คำตอบ
(B)
5
29
Which of these pairs are synthetic and natural macromolecules respectively?
คำตอบ
(C)
Nylon and creatine, polyethylene and haemoglobin
30
Ordinary glass is manufactured from silica, CaCO3 and
คำตอบ
(A)
Na2CO3
31
A red precipitate of copper (I) carbide is formed when ammonium solution of copper (I) chloride is introduced into
คำตอบ
(C)
HC≡CH
32
The boiling of fat and aqueous caustic soda is referred to as
คำตอบ
(D)
saponification
33
The most important use of hydrogen is in the
คำตอบ
(A)
manufacture of ammonia
34
which of the following polymers is suitable for packaging and electrical insulation?
คำตอบ
(D)
polystyrene
35
Hydrogen is readily released when dilute hydrochloric acid reacts with
คำตอบ
(B)
Na
36
The intermediate product formed when ethanol is progressively oxidized to ethanoic acid with potassium heptaoxodichromate (IV) is
คำตอบ
(B)
ethanal
37
A rock sample was added to cold dilute HNO3. The gas evolved was passed into a solution of acidified K2Cr2O7 and the solution turned green. The sample contains
คำตอบ
(C)
SO32-
38
Which of the following statement is true of a proton?
คำตอบ
(A)
The mass of a proton is 1840 times the mass of electron
39
Which of the following chloride would exhibit the least ionic character?
คำตอบ
(D)
AlCl3
40
A fixed mass of gas has a volume of 92\(cm^3\) at 3ºC. What will be its volume at 18ºC if the pressure remains constant?
คำตอบ
(D)
97.0cm3
41
The processes which return carbon (IV) oxide to the atmosphere include
คำตอบ
(A)
respiration, decay and combustion
42
The postulate of Dalton's atomic theory which still holds is that
คำตอบ
(A)
atoms can neither be created nor destroyed
43
\(^{14}\) \(_6\)C → X + β
X in the equation above represents
คำตอบ
(C)
147N
44
If 0.75 mole of cyclopropane and 0.66 mole of oxygen are mixed in vessel with a total pressure of 0.7 atmosphere, what is the partial pressure of oxygen in the mixture
คำตอบ
(D)
0.33 atmosphere
45
In the diagram above, the curve that represents the production of oxgyen gas from the decomposition of KCIO3 in the presence of MnO2 catalyst is
