AMS
1
ACJC 2008 H2 PRELIM P1
2
3
Atomic Structure
"All that glitter is not gold"
Act II - Scene VII - Prince of Morocco-William Shake Spear
Diamond is a simply a piece of charcoal that handled stress Exceptionally well
FALSE
Its an allotrope of Carbon where the Carbon atoms are arranged in a variation of the Face-Centred CUBIC crystal
structure called Diamond Lattices
4
5
6
7
Chemical Bonding
8
4
An ion IF4n− has a square planar structure as shown below:
n−
nF
F
I
F
F
What is the value of n?
A
5
1
B
2
C
3
D
4
Ice is the crystalline form of water. The diagram below shows part of the structure of ice.
- - - - Hydrogen bond
Which of the following statements is not true about ice?
A
Ice has a lower density than water at 0 oC due to its open structure.
B
The bond angle about oxygen in ice is 109.5o.
C
Ice does not conduct electricity.
D
Ice has a giant covalent structure.
HCI 2010 P1 H2 CHEM
9
10
Gases
Nobel Gases
11
Gases
5
The Van der Waal’s equation for a non-ideal gas is
an2
(P +
)(V - nb) = nRT
V2
The term b is a correction for
A
the space occupied by real molecules.
B
collisions between real molecules not perfectly elastic.
C
the existence of attractive forces between real molecules.
D
the existence of repulsive forces between real molecules.
3 (a)
The industrial liquefaction of N2O3 involves its compression.
Suggest why the compression of N2O3 into a region of high pressure is an
exothermic reaction. Why does the application of pressure cause the gas to
liquefy at room temperature?
B (i) N2O3 is unstable above room temperature and decomposes to NO2 and NO. A 2.5 g of
sample N2O3 was allowed to decompose completely in a 0.20 dm3 vessel at 65oC. Calculate the
total pressure in the vessel.
12
(ii) The total pressure in the vessel was found to be different from the value in (b)(i). Suggest a reason
for the discrepancy.
(c)
The following sketch represents the distribution of molecular speeds of N2O3 at 65°C.
On the same axes, draw the distribution of the molecular speeds of NO.
Fraction of
molecules
Molecular
speed
Explain your answer.
4444444444444444444444444444444444.
4444444444444444444444444444444444.
4444444444444444444444444444444444.
[2]
NJC 2010 P2
13
Energetic
Which is energetically more stable of the Carbon allotropes
Graphite or Diamond ??
Answer: Graphite.
Next, Why Diamond does not decompose to graphite?
(Its just a carbon)
14
RJC 2009 P3
15
16
17
18
Reaction Kinetic
What happened??
19
20
21
Chemical Equilibra
22
23
24
Acid/Base (Ionic)
4
The table below shows the dissociation equations of hydrofluoric acid, methanoic acid and disodium
hydrogen phosphate and the values of their respective dissociation constants. You are to use the
following information to answer (a) and (b).
3
Dissociation constants / mol dm−
Dissociation equations
HF + H2O
F− + H3O
HCOOH + H2O
2−
+
Ka = 6.8 x 10−4
HCOO− + H3O
+
H2PO4− + OH−
HPO4
+ H2O
(a)
For the following reaction:
H2PO4− + F−
(i)
Ka = 1.8 x 10−4
Kb = 1.6 x 10−7
HPO42− + HF
identify the one conjugate acid-base pair,
25
(ii)
predict, with reasons whether the equilibrium constant will be greater than
or less than 1.
(b)
Two solutions of pH 4.00 were prepared.
•
•
Solution A contains 0.0113 mol dm−3 methanoic acid and 0.0200 mol dm−3 sodium methanoate
Solution B contains 0.00113 mol dm−3 methanoic acid and 0.00200 mol dm−3 sodium methanoate
(i)
Calculate the change in pH when 0.0500 cm3 of 1.000 mol dm−3 HCl is added to 100.0 cm3 of
each of the two solutions. In this part, give your final answers to 3 siginificant figures.
(ii)
Explain the difference in the buffering effect of the two solutions.
[5]
H2 Chemistry 9647/02/NYJC J2/10 P2
26
27
28
29
The solubility product of some Group II fluorides, at 25oC, are given in the table below:
(a)
(i) Which of the above fluorides is most soluble and what is its solubility,
in mol dm-3, at 25 oC?
(ii) Briefly explain how the solubility of the fluoride in (i) would change if it is
dissolved in an aqueous KF solution.
(b)
A researcher accidentally mixed 50.0 cm3 of 0.200 mol dm-3 CaCl2 solution with 25.0 cm3 of
0.100 mol dm-3 BaCl2 solution in the laboratory.
To separate the two metals ions, he added just enough solid KF to precipitate the maximum
amount of CaF2 from the mixture.
(i) Calculate the minimum concentration of fluoride ions required to cause
precipitation of BaF2.
(ii) Hence, calculate the concentration of Ca2+ ions in the solution when the first
trace of BaF2 appears.
[Total: 6]
30
Organic Chemistry
This is a real molecule, which was synthesize via chemical means.
Its purpose is still unknown to date, because the chemist who did it felt that it was cute.
J. Org. Chem., 2003, 68 (23), pp 8750–8766
31
32
33
.SAJC 2011
34
35
36
1. Give the IUPAC name of each of the following organic compounds ( And skeletal structure)
(a) CH3CH(CH3)CH2CH2CH3
(b) CH2=CHCH(CH3)C(CH3)3
37
38
39
40