Exercise (Module: Atoms and Molecules)
IJSO Training: Atoms and Molecules
Exercise
1.
Give 2 examples for each of the following:
(a) Elements
(b) Compounds
(c) Ionic compounds with monoatomic ions only
(d) Ionic compounds with polyatomic ions
(e) Covalent compounds
(f) Compounds capable of forming hydrogen bond
(g) Gaseous elements
(h) Liquid elements
(i) Elements that form stable ions of +1 charge
(j) Elements that form stable ions of +2 charge
(k)
(l)
(m)
(n)
2.
Which of the following is/are good conductor(s) of electricity at room
temperature?
(a)
(b)
(c)
(d)
(e)
(f)
(g)
3.
Elements that form stable ions of -1 charge
Elements that form stable ions of -2 charge
Elements that form stable monoatomic molecules
Elements that form stable diatomic molecules
Aluminium
Iodine
Phosphorus
Sulphur
Carbon (graphite)
Mercury
Sodium chloride
Which of the following is/are good conductor(s) of electricity in molten state?
(a)
(b)
(c)
(d)
(e)
(f)
Calcium
Sodium chloride
Sugar
Iodine
Sulphur
Lead bromide
Exercise (Module: Atoms and Molecules)
4.
Which of the following has/have similar chemical properties as sodium?
(a)
(b)
(c)
(d)
(e)
5.
Magnesium
Cesium
Lithium
Hydrogen
Calcium
Which element has the largest atomic radius?
(a) Na
(b) Mg
(c) K
(d) Al
6.
Which element has the highest melting point?
(a)
(b)
(c)
(d)
7.
Sodium
Magnesium
Potassium
Calcium
Which element is hardest?
(a) Phosphorus
(b) Sodium
(c) Magnesium
(d) Chromium
8.
Who proposed the Plum Pudding Atomic Model?
(a) John Dalton
(b) J. J. Thomson
(c) D. I. Mendeleev
(d) E. Rutherford
Exercise (Module: Atoms and Molecules)
9.
Magnesium has three stable isotopes, 24Mg, 25Mg and 26Mg.
Their atomic
masses and natural abundances are shown below. Calculate the relative atomic
mass of magnesium.
Isotope
Atomic mass (au)
Natural abundance (%)
24
Mg
23.9850
78.99
25
Mg
24.9858
10.00
26
Mg
25.9826
11.01
10. Strontium has four stable isotopes, 84Sr, 86Sr, 87Sr, and 88Sr. Their atomic
masses and natural abundances are shown below. Calculate the relative atomic
mass of strontium.
Isotope
Atomic mass (au)
Natural abundance (%)
84
83.9134
0.56
86
85.9093
9.86
87
86.9089
7.00
88
87.9056
82.58
Sr
Sr
Sr
Sr
11. Give the numbers of protons, neutrons and electrons that present in the following
species.
Species
24
No. of protons
No. of neutrons
No. of electrons
2+
(a) Mg
(b) 37Cl-
(c) 40Ca2+
(d) CO32(e) SO42Consider the most abundant isotopes for item (d) and (e)
12. An element forms stable 2+ ions that have the same electron configuration as
argon. What is the element?
13. Give the electron arrangements of the following elements:
(a) Chlorine (atomic number 17)
(b) Calcium (atomic number 20)
(c) Nickel (atomic number 28)
(d) Zinc (atomic number 30)
(e) Arsenic (atomic number 33)
(f) Bromine (atomic number 35)
Exercise (Module: Atoms and Molecules)
14. Balance the following chemical equations:
(a) Pb(NO3)2 + NaCl 
PbCl2 + NaNO3
(b) C2H5OH + O2
 H2O + CO2
(c) CCl4 + SbF3 
CCl2F2 + SbCl3
(Advanced exercises – balancing redox reaction – the total charges on both sides
must also be balanced)
(d) MnO4- + Fe2+ + H+  Mn2+ + Fe3+ + H2O
(e) MnO4- + C2O4- + H+  Mn2+ + CO2 + H2O
15. Calculate the volume of CO2 produced from burring 14 mL of C2H5OH (ethanol).
Assume the gas volume was measured at 25oC and 1 atm. (Ethanol: density =
0.789 g cm-3, MW = 46.0688)
16. How many oxygen atoms are present in 12.5 g of calcium carbonate?
17. What is the mass of H2O produced from the combustion of 15 g of CH4?
18. Calculate the volume of CO2 produced from the combustion of 1.000 kg of
gasoline? (assuming that the gasoline is composed of 100% octane – C8H18, and
the gas volume is measured at 25oC and 1 atm)
19. What is the volume of CO2 produced from the reaction of 4.5 g of CaCO3 with
excess acid? Assume the gas volume was measured at 25oC and 1 atm.
20. What is the volume of H2 produced from the reaction of 2.4 g of sodium metal
with water? Assume the gas volume was measured at 25oC and 1 atm.
Exercise (Module: Atoms and Molecules)
21. Shown below is the chemical structure of a common drug – aspirin.
Give the
number of:
O
OH
C
O
HC
HC
O
C
C
CH
CH3
C
H
(a)  bonds
(b)  bonds
(c) sp3 hybridized atoms
(d) sp2 hybridized atoms
(e) lone-pair electrons
(f) carbon atoms having the trigonal planar geometry
(g) atoms having the tetrahedral geometry
22. Which of the following compounds has sp hybridized carbon atom?
(a) H2C=CH2
(b) H2C=O
(c) CO2
(d) CH4
23. Briefly explain why BF3 has a trigonal planar structure while BF4- has a
tetrahedral structure. (hint: consider the hybridization of the boron atom)
24. Which of the following compounds has the shortest C-H bond?
(a) CH4
(b) H2C=CH2
(c) HC≡CH
(d) H2C=O
25. Which of the following elements forms coloured ions?
(a) Aluminium
(b) Nickel
(c) Cesium
(d) Lead
Exercise (Module: Atoms and Molecules)
26. Which element has the highest electronegativity?
(a)
(b)
(c)
(d)
Fluorine
Oxygen
Bromine
Nitrogen
27. Which of the following type of intermolecular interactions are present in
ammonia?
(a) hydrogen bonding
(b) dipole dipole interaction
(c) ion dipole interaction
(d) induced-dipole induced-dipole interaction.
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