Nitrogen Activation in a Mars–van Krevelen
... semiempirical approach. We show that 3-fold hollow bound nitrogen-containing (111)-surfaces have surprisingly high concentrations (1.6 × 1016 to 3.7 × 1016 cm−2) of nitrogen vacancies in the temperature range for ammonia synthesis. It is shown that these vacancy sites can adsorb and activate N2 demo ...
... semiempirical approach. We show that 3-fold hollow bound nitrogen-containing (111)-surfaces have surprisingly high concentrations (1.6 × 1016 to 3.7 × 1016 cm−2) of nitrogen vacancies in the temperature range for ammonia synthesis. It is shown that these vacancy sites can adsorb and activate N2 demo ...
Fall Final Rev 2014
... 25. a. Exothermic reactions release energy; endothermic reactions absorb energy b. i. exothermic, 57 kJ ii. endothermic, 5.2 mol 26. a. i. Gas pressure is caused by collisions of gas molecules with container wall. ii. Gas temperature is proportional to molecular kinetic energy. iii. Molecules have l ...
... 25. a. Exothermic reactions release energy; endothermic reactions absorb energy b. i. exothermic, 57 kJ ii. endothermic, 5.2 mol 26. a. i. Gas pressure is caused by collisions of gas molecules with container wall. ii. Gas temperature is proportional to molecular kinetic energy. iii. Molecules have l ...
PRACTICE EXAM for FALL 2013 FINAL EXAM (Unit 6 + review) 1
... 25. a. Exothermic reactions release energy; endothermic reactions absorb energy b. i. exothermic, 57 kJ ii. endothermic, 5.2 mol 26. a. i. Gas pressure is caused by collisions of gas molecules with container wall. ii. Gas temperature is proportional to molecular kinetic energy. iii. Molecules have l ...
... 25. a. Exothermic reactions release energy; endothermic reactions absorb energy b. i. exothermic, 57 kJ ii. endothermic, 5.2 mol 26. a. i. Gas pressure is caused by collisions of gas molecules with container wall. ii. Gas temperature is proportional to molecular kinetic energy. iii. Molecules have l ...
Ministry of Education and Science of the Ukraine
... chemical element. Balancing redox equations. Biological role of redox reactions. sand p- block chemical elements and their properties. Metals and nonmetals. Molecules and ions. Classification of biogenic elements. Macrominerals. 2. Biogenic d- block elements: biological role, application in medicine ...
... chemical element. Balancing redox equations. Biological role of redox reactions. sand p- block chemical elements and their properties. Metals and nonmetals. Molecules and ions. Classification of biogenic elements. Macrominerals. 2. Biogenic d- block elements: biological role, application in medicine ...
Hydrogen storage of calcium atoms adsorbed on graphene: First
... store 8.4 wt % hydrogen. Their result, which is crucial for safe and efficient hydrogen storage7, inspired us to consider graphene as the substrate material for Ca atoms. Graphene is precursor to C60 and carbon nanotubes, but being a single atomic plane of graphite its both sides may be suitable for ...
... store 8.4 wt % hydrogen. Their result, which is crucial for safe and efficient hydrogen storage7, inspired us to consider graphene as the substrate material for Ca atoms. Graphene is precursor to C60 and carbon nanotubes, but being a single atomic plane of graphite its both sides may be suitable for ...
(1/V m C) +
... 11). Write Gibb`s adsorption isotherm. Explain the term involved. Gibbs derived a thermodynamic relationship between the surface or interfacial tension γ and the surface excess Γ (adsorption per unit area). At constant temperature, the Gibbs adsorption equation is dγ = −∑(ni/A)dμI = −∑ΓidμI, whe ...
... 11). Write Gibb`s adsorption isotherm. Explain the term involved. Gibbs derived a thermodynamic relationship between the surface or interfacial tension γ and the surface excess Γ (adsorption per unit area). At constant temperature, the Gibbs adsorption equation is dγ = −∑(ni/A)dμI = −∑ΓidμI, whe ...
KEMS448 Physical Chemistry Advanced Laboratory Work
... In this laboratory work, the surface tension of an anionic tenside molecule, sodium dodecyl sulphate (NDS), is measured as a function of concentration. From the results, the critical micelle concentration is determined and the behaviour of surface excess as a function of the concentration is examine ...
... In this laboratory work, the surface tension of an anionic tenside molecule, sodium dodecyl sulphate (NDS), is measured as a function of concentration. From the results, the critical micelle concentration is determined and the behaviour of surface excess as a function of the concentration is examine ...
Modeling CO Oxidation on Silica-Supported Iron Oxide under
... Fe2O3 and NiO by temperature-programmed desorption, Iwamoto et al. (1976, 1978a,b) have demonstrated the existence of at least four states of adsorbed oxygen, the maxima of which appeared at 50-300 (R), 350-360 (β), 480-490 (γ), and >600 °C (δ), respectively. γ and δ oxygen were assigned to O- speci ...
... Fe2O3 and NiO by temperature-programmed desorption, Iwamoto et al. (1976, 1978a,b) have demonstrated the existence of at least four states of adsorbed oxygen, the maxima of which appeared at 50-300 (R), 350-360 (β), 480-490 (γ), and >600 °C (δ), respectively. γ and δ oxygen were assigned to O- speci ...
Chem152
... 47. If 1.500 g of vanadium metal react with oxygen gas to give 2.679 g of vanadium oxide, what is the empirical formula of the product? A) VO B) V2O3 C) V2O5 D) V3O2 E) V5O2 48. Fructose is a sugar found in fruit and honey. Calculate the empirical formula for fructose given its percent composition: ...
... 47. If 1.500 g of vanadium metal react with oxygen gas to give 2.679 g of vanadium oxide, what is the empirical formula of the product? A) VO B) V2O3 C) V2O5 D) V3O2 E) V5O2 48. Fructose is a sugar found in fruit and honey. Calculate the empirical formula for fructose given its percent composition: ...
3. Theory Crystallization is a separation and purification technique
... zero. For α < 1, however, the step velocity never approaches zero but approaches a nonzero value as Kcimp is increased. This value is increasing with smaller α and is one at a value of α = 0. If an equilibrium adsorption is assumed for an impurity [49, 77], the surface coverage θ in Eq. 3.36 is repl ...
... zero. For α < 1, however, the step velocity never approaches zero but approaches a nonzero value as Kcimp is increased. This value is increasing with smaller α and is one at a value of α = 0. If an equilibrium adsorption is assumed for an impurity [49, 77], the surface coverage θ in Eq. 3.36 is repl ...
Lifting Fingerprints with Powders and Chemicals
... the property to sublime. Iodine is a solid crystal that, when heated, is transformed into a vapor without passing through a liquid phase. The suspect material is usually placed in an enclosed cabinet with iodine crystals. While heated, the vapors will combine with the constituents of the latent prin ...
... the property to sublime. Iodine is a solid crystal that, when heated, is transformed into a vapor without passing through a liquid phase. The suspect material is usually placed in an enclosed cabinet with iodine crystals. While heated, the vapors will combine with the constituents of the latent prin ...
Molecular diffusion at surfaces
... of the square move 0.18 A away to a distance of 2.09 A and the other two Fe atoms at corners of the other side also relax 0.12 A away. The four Fe atom surrounding the two Fe atoms at the apexes move 0.18 A. The other four atoms surrounding the two Fe atoms close to C move 0. 13 A. Twelve more surro ...
... of the square move 0.18 A away to a distance of 2.09 A and the other two Fe atoms at corners of the other side also relax 0.12 A away. The four Fe atom surrounding the two Fe atoms at the apexes move 0.18 A. The other four atoms surrounding the two Fe atoms close to C move 0. 13 A. Twelve more surro ...
Adsorption
Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid (the absorbate) permeates or is dissolved by a liquid or solid (the absorbent). Adsorption is a surface-based process while absorption involves the whole volume of the material. The term sorption encompasses both processes, while desorption is the reverse of it. Adsorption is a surface phenomenon.Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent, or metallic) of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption (characteristic of weak van der Waals forces) or chemisorption (characteristic of covalent bonding). It may also occur due to electrostatic attraction.Adsorption is present in many natural, physical, biological, and chemical systems, and is widely used in industrial applications such as activated charcoal, capturing and using waste heat to provide cold water for air conditioning and other process requirements (adsorption chillers), synthetic resins, increase storage capacity of carbide-derived carbons, and water purification. Adsorption, ion exchange, and chromatography are sorption processes in which certain adsorbates are selectively transferred from the fluid phase to the surface of insoluble, rigid particles suspended in a vessel or packed in a column. Pharmaceutical industry applications, which use adsorption as a means to prolong neurological exposure to specific drugs or parts thereof, are lesser known.However, it should be remarked that the distinction between adsorption and absorption vanishes as we go from perfectly crystalline macroscopic materials to porous/structured materials, aggregates and composites made out of increasingly smaller grains, viz., micron-sized particles to nanoparticles, sub-nano particles and finally molecules (or atoms). In such nano-composites, the internal surface area of particulate matter is very large. Then the adsorption on internal surfaces simply becomes absorption when viewed from the bulk. Then the distinction between adsorption and absorption vanishes. On the other hand, the distinction is clearest between bulk solids without internal structure, but having only surfaces where only adsorption can occur on the outer surfaces, and nanocomposites or aggregates with internal structure where absorption by the host material is simply adsorption on internal surfaces of the host material. As an example, we may consider a crystalline piece of silicon dioxide (quartz) which can adsorb water molecules on its surface. However, if the quartz is ground into very fine sand, the pile of sand (an aggregate) has a very large internal surface area. A very large amount of water can be adsorbed by the ""internal"" surfaces of the grains in the pile of sand, and this absorption is simply ""internal adsorption. If water is made to flow thorugh such a pile of sand, ions and toxins in the water may be preferentially adsorbed by the surfaces of the grains of sand, providing a simple, well-known water purification application.The word ""adsorption"" was coined in 1881 by German physicist Heinrich Kayser (1853-1940).