lobna.nassr

Lobna Abdel-Mohsen Ebaid Nassr

Professor - Director of Quality Management Unit - Faculty of Science - Sohag University

Faculty of science

Address: Chemistry Department - Faculty of Science - Sohag University

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2018-11-29 01:09:09 | 23 | Chemical kinetics 321 C
Acid / base  effect on an enzym
Deduce the relation between the reaction rate and substrate concentration for an enzym "HE" in both acidic and basic medium. Concerning the following: Kb=[H+][HE]/[H2E+] Ka=[H+][E-]/[HE] 0[E] = [HE] + [HES] + [H2E+] + [E-] Read more

2018-11-29 00:50:41 | 35 | Kinetic Theory 321 C
nonideal behavior of Gases
If 1.000 mol of an ideal gas were confined to 22.41 L at 0.0°C, it would exert a pressure of 1.000 atm. Use the van der Waals equation to estimate the pressure exerted by 1.000 mol of Cl2(_g_) in 22.41 L at 0.0°C (a = 6.49 L2-atm/mol2, b = 0.0562 , R = 0.08206 L-atm/mol-K). Read more

2018-11-13 11:46:55 | 136 | Physical Chemistry 251 C
The units of different Rate constants
The units of different Rate constants The _order_ of a rate law is the sum of the exponents of its concentration terms. Once the rate law of a reaction has been determined, that same law can be used to understand more fully the composition of the reaction mixture. More specifically, the reaction order is the exponent to which the concentration ... Read more

2018-10-30 11:36:41 | 317 | Physical Chemistry 251 C
First order Reaction
The RATE LAW or RATE EQUATION for a chemical reaction is an equation that links the reaction rate with the concentrations or pressures of the reactants and constant parameters (normally rate coefficients and partial reaction orders). A first order reaction depends on the concentration of only one reactant (a unimolecular reaction) IN 1ST ORDER REACTION:IN 1ST ORDER REACTION:IN 1ST ORDER ... Read more

2018-10-17 20:23:55 | 21 | Kinetic Theory 321 C
Total and Average Kinetic Energy
[1] A tank used for filling helium balloons has a volume of 0.300 m3 and contains 2.00 mol of helium gas at 20.0°C. Assume that the helium behaves like an ideal gas. (A) What is the total translational kinetic energy of the gas molecules? (B) What is the average kinetic energy per molecule? [2] What if the temperature is raised ... Read more

2018-10-17 20:06:42 | 47 | Transition Elements 311 C
Charge Transfer
The observed color of a substance can be determined from the color of the light absorbed. What is “seen” is the complimentary colors. When light passes through a material some wavelengths are absorbed. If absorption occurs in the visible region of the spectrum, the transmitted light is coloured with the complementary colour to the colour of the light absorbed. Absorption ... Read more

Give reasons
_Haemoglobin _is an essential component of the blood. The central, active part of the molecule comprises a haem ring (as above) at the centre of which lies an iron ion. We call it a charge transfer _couple_, since it requires two constituents, both the iron and the haem. An old-fashioned way of removing the stain caused by blood is to ... Read more

2018-09-26 20:40:51 | 62 | Chemical kinetics 321 C
Parallel and consecutive reactions
PARALLEL REACTIONS In the parallel reactions, a single reactant may be converted into several different products simultaneously. There are numerous examples of such reactions in organic chemistry. SERIES (CONSECUTIVE) FIRST-ORDER REACTIONS A similar situation of CONSECUTIVE REACTION is nuclear chemistry where a nuclide decays to a daughter nuclide that is also radioactive and undergoes decay. COMPARE BETWEEN THE KINETICS OF ... Read more

2018-09-26 19:48:55 | 31 | Kinetic Theory 321 C
Laws of Gases
THE GAS LAWSTHE GAS LAWS were developed at the end of the 18th century, when scientists began to realize that relationships between pressure, volume and temperature of a sample of gas could be obtained which would hold to approximation for all gases. Gases behave in a similar way over a wide variety of conditions because they all have molecules which ... Read more

2018-09-22 22:10:27 | 81 | Transition Elements 311 C
Lanthanide contraction
The elements following the lanthanides in the periodic table are influenced by the lanthanide contraction. The radii of the period-6 transition metals are smaller than would be expected if there were no lanthanides, and are in fact very similar to the radii of the period-5 transition metals, since the effect of the additional electron shell is almost entirely offset by ... Read more