27th of Oct. 2024
Université M’Hamed Bouguerra Boumerdes
Electric and electronic engineering Institute
atomistics -Recitation N°2
Ex1
a) 25.0 gm of sample of ferrous sulphate was dissolved in water containing dil. H 2SO4 and the
volume made up to one litre. 25 ml of this solution required 20ml of N/10 KMnO4 solution of
complete oxidation. Calculate the percentage of FeSO4.7H2O in the given sample. (Fe=56,
Mn=55, K=39, S=32, O=16)
b) Calculate th weight of a sample of commercial sodium carbonate present in 100ml. of
solution, if 10ml of the solution required 12ml of N/10HCl solution for neutralization. The
sample of the sodium carbonate is 63,6 % pure. (c=12, Na=23, O=16)
Ex2
Pyrolysis at normal conditions of 10 grams (combustion) of a compound containing H, O, N,
and sulphur (S), leads to the formation of the following masses of gases: 4.848grams of SO2,
1.288 grams of NH3, 3.484 grams of NO2 and 0,357grams of hydrogen (H2).
Deduce the structural formula for the compound.
Ex3
Determine the empirical and molecular formulas of each of the following substances:
1. monosodium glutamate (MSG), a flavor enhancer in certain foods that contains 35.51% C,
4.77% H, 37.85% O, 8.29% N, and 13.60% Na, and has a molar mass of 169 g/mol
2. 32.90% Na, 12.82% Al, and 54.30% F and a molar mass of 210 g/mol. propose its molecular
structure.
Ex 3
Volume and specific volume of the nucleus
The radius of the nucleus is given by R = R0 A 1/ 3, where A is the number of nucleons.
Calculate the volume and the specific volume of nucleus of chemical elements?
Take examples of 20782Pb, 13355 Cs; 6.943Li nuclei
Compare the results to that of the whole atom. What’s your conclusion?
Avogadro Number Na = 6.02 x 1023; R0 = 1.2x10-15
Ex4
An observed deviation on a screen placed at a distance L from the entrance of two parallel
plate’s capacitor, resulted from the action of an electrical field E on charged particles. They
penetrate into the capacitor at a speed of V0, and deviate to the positive plate.
a) Give the analytical expression of the deviation
b) Calculate the mass of these particles
c) What is the value of the electrical field necessary to accelerate these particles
d) Give the potential acceleration
Take: L=5cm, y (deviation) = 2cm E= 40000 V/m; e/m= 1.76x10 11cb/kg
Ex5
In a mass spectrometer constituted from two parallel plate’s capacitor an ion is passed
through at a velocity V0=6.0 x105m/sec to get a deviation y = 3.17mm, the electrical voltage
applied is U=1000 volts. The gap opening d= 2cm and the length of the capacitor L =8cm.
Identify the element if the particle is charged positively with 2 e.
Ex6
A compound used as a superconductor material is constituted from unknown X1, X2
chemical elements and oxygen O.
▪ Mass spectroscopy is performed on the unknown elements X1 and X2, the obtained charges to
masses ratios are: [q/m] X1= 7.02x105cb/kg and [q/m] X2 = 4.63x105 cb/kg.
▪ The percentage compositions are: %x1= 34.82% %x2= 53% and % O= 12.17%. Determine
the empirical and molecular formula of the product if the molecular weight M w is 393.3
g/mol.