CHEMISTRY TEST

Chemistry Test

Chemistry Test

Test 1)

The molecular mass of the I2 is 254 grams.

(Atomic mass of I : 127

Molecular mass of I2 = 2 X 127= 254 grams)

The molecular mass of I2 has 6.022 X 10^23 molecules, which means that 254 grams contain 6.022 X 10^23 molecules.

So 240 grams of Iodine has (6.022 X 10^23 / 254) X 240 molecules, which is equal to 5.69 X 10^23 molecules.

The molecular mass of CO (carbon monoxide) is 28 grams.

(Atomic mass of C + Atomic mass of O = 12 + 16 = 28)

The molecular mass contains 6.022 X 10^23 molecules, which means

28 grams contain 6.022 X 10^23 molecules

So 8.60 X 10^22 molecules represent 28/(6.022 X 10^23 molecules) X 8.60 X 10^22 , which is equal to 3.99~4grams.

Atomic weight for I = 126.9 g/mol, atomic weight for I2 = 253.8 g/mol

Atomic weight for C = 12.01 g/mol, atomic weight for O = 16 g/mol

Atomic weight for CO = 28.01 g/mol

240 g / (253.8 g/mol) = 0.945626 moles * 6.022 * 10^23 (avogadro's constant) = 5.6946 * 10^23 molecules of I2 (Iodide)

8.60 * 10^22 molecules / 6.022 * 10^23 = 0.1428 moles of CO (Carbon monoxide), 0.1428 mol * 28.01 g/mol = 4.00 grams of CO

Test 2)

Answer 1)

A semi-empirical relation which can be used to determine the total attenuation cross sections of samples containing H, C, N and O in the energy range 145-1332 keV has been derived based on the total attenuation cross sections of several sugars, amino acids and fatty acids. The semi-empirical relation can reproduce the experimental values within 1-2%.

Answer 2)

The total attenuation cross sections of five elements carbon, aluminium, titanium, copper and zirconium measured in the same experimental set-up at the energies mentioned above have been used in a new matrix method to evaluate the effective atomic numbers and the effective electron densities of samples such as cholesterol, fatty acids, sugars and amino acids containing H, C, N and O atoms from their effective atomic cross sections.

Test 3)

There are two main families of MD methods, which can be distinguished according to the model (and the resulting mathematical formalism) chosen to represent a physical system. In the 'classical' mechanics approach to MD simulations, molecules are treated as classical objects, resembling very much the 'ball-and-stick' model. Atoms correspond to soft balls and elastic sticks correspond to bonds. The laws of classical mechanics define the dynamics of the system. The 'quantum' or 'first-principles' MD simulations, which started in the 1980s with the seminal work of Car and Parrinello, take explicitly into account the quantum nature of the chemical bond. The electron density function for the valence electrons that determine bonding in the system is computed using quantum equations, whereas the dynamics of ions (nuclei with their inner electrons) is followed classically.

Test 4)

Question 1

In the reaction

Cu + HNO3 ? Cu2+ + NO2 + H2O

Deduce the oxidation state of all the elements.

Cu: 0 H: +1 O: -2 N: +5 RHS: Cu: 0 N: +4 O: -2 H: +1 O: ...