E-Learning : Médecine et Pharmacie

Department of Pharmacy, Faculty of Medicine, Batna-2 University

Pharmaceutical general chemistry module

Academic year 2023/2024

professor in charge : Pr. Bitam F 

Tutorial 1 (Chapter 1 and 2)

Exercise 1: Around the atom

A)Answer true or false

1) J.J Thomson's experiment clarifies the calculation of the mass of the electron.

2) The negative charge of the electron was determined by the oil drop at one time.

B)The mass of elementary particles is approximately: 

1) 1 u for the proton, neutron and electron.

2) 1 u for the proton, the neutron but 1836 u for the electron.

3) 1 u for the proton, the neutron but 1/1836 u for the electron.

4) 10^-19g for the proton, the neutron and 1836 times less for the electron.

C)Around the isotopes

1) The number of protons explains the existence of isotopes.

2) The rubidium ⁸⁷Rb posses 37 protons, 37 electrons and 50 neutrons.

3) ¹⁴₇N and ¹⁵₇N are two isotopes. 

 4) ⁷₃Li⁺³and ⁷₃Li are two isotopes.

5) The uranium has the atomic number 92 and exists essentially, in natural state, under the form       of two isotopes: ²³⁵U and ²³⁸U. 

a) Give the definition of the unit of atomic mass and calculate its value in g. 

b) Calculate the atomic molar masses of each isotope in g.mol^-1.

c) Determine the proportion of ²³⁵U in natural uranium.

Data: Molar masse of element: m (U) = 238,0289 g.mol^-1, atomic masses: m (²³⁵U) = 235,0439 u ; m (²³⁸U) = 238,0508 u.

Exercice 2:  Photoelectric Effect 

The threshold energy is equal to 3.65 10^-19J. 

a) Determine threshold frequency of sodium 

From this threshold frequency,

b) calculate the cinetic energy of electrons that will be ejected if the sodium surface is exposed at ultraviolet rayons of which the wavelength equal 180 nm.

Exercice 3 :Around Bohr's theory 

Q1:

1) Bohr's theory did not make it possible to find the frequencies of the lines of the hydrogen spectrum.

2) The hydrogen spectrum is a discontinuous spectrum emission lines.

3) The frequency wave length is equal to ν=10¹⁵ is visible.

4) The Lyman series is in the IR range. 

5) The expression λ= R_H(1-1/m²) represents the entire hydrogen emission spectrum

Q2:we give the energy levels of the hydrogen atom E₁= -13.6 ev, E₂= -3.4 ev E₃= -1.5 ev E₄= -0.85 ev.

1) The excitation of a hydrogen atom from its fundamental state can be accompanied by :

2) The emission of 10.2 ev of photons.

3) The absorption of 12.1 ev of photons 

4) The absorption of 1.9 ev of photons

 5) The emission of 5.10^-18of photons

Q3:The limits of Bohr model

1) The Bohr model presents a contradiction with classical mechanics

2) The Bohr model does not explain all the lines in the emission spectra of polyelectronic atoms.

3) For a very low mass particle, it is not possible to determine, simultaneously and precisely, its position and its acceleration. 

4) Quantum mechanics will replace classical mechanics by defining the electron by its energy and its probability of presence at a point in space.

Q4 : The energy required to ionize the ₄Be³⁺ion from its ground state is: 

A) 54.4ev 

B) 122.4ev 

C) 217.6ev 

D) 220.6ev

Exercice 4 :

A)About the Li⁺²ion :  

1) Calculate in joules and ev, the third ionization energy of Lithium.

2) Calculate the wavelength and frequency of the line corresponding between the energy levels from  n=4  to n= 1

3)  What is the smallest energy value that the ion B₅⁺⁴must absorb to pass from the fundamental state to the excited state.

 4) If this energy was emitted by a photon, what is the corresponding wave length ?

B) After absorbing a photon, a hydrogenoid ion is excited from its fundamental state to the state n° = 3. 

1) Write the relation that relied the wave length λ_1-3of the absorbed photon with E₀, Z, ℎand C.

2) Knowing that λ_1-3 is equal to 11.4 nm, identify the hydrogenoid ion.

3) Knowing that the electron is excited from the level 3 to the level 6, so if the hydrogenoid ion absorbs a photon of wave length 360 nm from the state n = 6, What is going on ? Justify.