Page 8 - PRE-U STPM CHEMISTRY TERM 1

Chemistry Term 1 STPM
6 The relationship between the wave length (λ) and the frequency (f)
of the electromagnetic radiation is given by:
λf = C
–1
8
[where C = velocity of light = 3.0  10 m s ]
CHAPTER 7 The diagram below shows the various types of electromagnetic
radiations.
2

Wavelength increasing

10 1 10 –2 10 –4 10 –6 10 –8 10 –10 10 –12 10 –14 Meter

Radio TV Microwaves Infrared Ultraviolet X-rays y-rays Cosmic
waves waves radiation Visible light radiation rays

3 10 8 3 10 10 3 10 12 3 10 14 3 10 16 3 10 18 3 10 20 3 10 22 1
Second
Frequency increasing

700 Red Orange Yellow Green Blue Violet 400 nm

Quantum theory 8 In 1900, Max Planck put forward his quantum theory which
states that energy in the form of electromagnetic radiation can be
emitted or absorbed in discrete amount (or packets) called quanta
(singular: quantum).
Concept of quanta 9 The magnitude of a quantum depends on the frequency (or
wavelength) of the radiation. The energy (in J) associated with a
quantum of energy (or a photon) is given by the Planck’s equation:
E = hf
Where h = Planck’s constant = 6.63  10 J s or
–34
= 3.99  10 kJ mol s
–1
–13
Quick Check 2.1

1 A quantum of a particular electromagnetic radiation has energy of 10 J. Calculate
–18
(a) the energy in kJ mol ,
–1
(b) the frequency, and
(c) the wavelength of the radiation.
2 A gamma radiation has a frequency of 1  10 Hz. Calculate
24
(a) its wavelength,
(b) its energy in J, and
–1
(c) its energy in kJ mol .

38

02 Chapter 2.indd 38 3/26/18 3:14 PM