Page 32 - PRE-U STPM CHEMISTRY TERM 1

Chemistry Term 1 STPM
Structured and Essay Questions

1 In the stratosphere, chlorine molecules absorb electromagnetic radiation and dissociate to produce
chlorine atoms which are responsible for the destruction of ozone.
CHAPTER Cl—Cl(g) → 2Cl(g)

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2 Given that the bond energy of chlorine is 242 kJ mol , calculate the wavelength of the light absorbed.
2 Part of the Lyman series in the hydrogen emission spectrum is as shown below:

8.22 10.27 10.62 10.97
6
Wave number ( 10 ) m –1
(a) Draw an energy level diagram to show how the lines are produced.
(b) (i) Define ionisation energy of hydrogen. Illustrate your answer with an appropriate equation.
(ii) Calculate the ionisation energy (in kJ mol ) of hydrogen from the above spectrum.
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3 The diagram below shows the lines in the Balmer series in the emission spectrum of hydrogen atom.
(a) Draw a labelled energy diagram to show how the lines marked X and Y are formed.
(b) Name two species that would produce similar emission spectrum as that of the hydrogen atom. Explain
your reasoning.

X Y
Frequency
4 The frequencies of the first five lines in the Lyman series of the hydrogen atom are given below:
2.47, 2.92, 3.08, 3.16, 3.20 ( 10 s )
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Plot a suitable graph to determine the ionisation energy of the hydrogen atom
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(a) in J, and (b) kJ mol .
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5 The first seven ionisation energies (kJ mol ) of an element D are as follows:
496, 4563, 6913, 9544, 13 352, 16 611, 20 115
(a) What do you understand by the term ionisation energy?
(b) Explain why the ionisation energy increases with the number of electrons removed.
(c) Plot a suitable graph or otherwise, determine the Group number of D in the Periodic Table. Explain how
you arrived at the answer.

6 (a) Sketch the energy level diagram for the orbitals of an atom with the principle quantum numbers of
n = 1 to n = 3 inclusive of the 4s orbital.
(b) Using arrows to represent electrons, show the electronic configuration of
(i) a carbon atom in its ground state.
(ii) a carbon atom in its excited state of lowest energy.
(iii) a carbon atom in its excited state with the highest energy.

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02 Chapter 2.indd 62 3/26/18 3:14 PM