Mole units

F, V, and L moles/unit time and their mole-fraction compositions are, respectively, w, y, and x. ... 

Partial molar quantities have per mole units, and for Yj this is understood to mean per mole of component i. The value of this coefficient depends on the overall composition of the mixture. Thus Vj o the same for a water-alcohol mixture that is 10% water as for one that is 90% water. 

Many cliciiiical reactions evolve or absorb heat. When applying energy balances (consenatioit law for energy) in tccluiical calculations the heat (enthalpy) of reaction is often indicated in mole units so that tliey can be directly applied to demonstrate its chemical change. To simplify the presentation that follows, examine the equation ... 

The equation for a chemical reaction speaks in terms of molecules or of moles. It contains the basis for stoichiometric calculations. However, in the laboratory a chemist measures amounts in such units as grams and milliliters. The first step in any quantitative calculation, then, is to convert the measured amounts to moles. In mole units, the balanced reaction connects quantities of reactants and products. Finally, the result is expressed in the desired units (which may not necessarily be the same as the original units). 

The mass transfer rate (moles/unit area and unit time) is given by equation 10.180, where denoting the original conditions by subscript 1 and the conditions at the higher temperature by subscript 2 gives ... 

The rate of removal of A (moles/unit time) by chemical reaction is ... 

The CHETAH programme used kcal/mole units whereas kJ/mole is used here. Nevertheless, numerous published documents give results using the old units. This is the reason it was decided to provide these group values in both units to be able to make calculations using both systems for comparative purposes. kJ is therefore retained. 

For conditions where the entrainment may be assumed constant across a tray, Colburn(62) has suggested that the following expression gives, for entrainment er (moles/unit time, unit area), a correction to EMv, so that the new value of efficiency Ea is given by ... 

If k[ is the mass transfer coefficient for the liquid phase in moles/unit time, unit area, unit mole fraction driving force, then ... 

L Liquid flowrate in mass or moles/unit time kg/s, kmol/s Mr1, nt-1... 

L Liquid flowrate, in moles/unit time-unit area kmol/m2s NL-2T- ... 

The position of A will depend on process conditions. For a well mixed crystallizer at steady state, point A will adjust until the rate of hemlhydrate dissolution equals the rate of gypsum growth (In mole units). In simplified terms. 

The mole unit and the gram formula unit are employed in similar calculations. For this reason, many chemists use the term mole to describe quantities of both molecular and nonmolecular substances. Try answering the following problems ... 

You should recall from the review of the mole unit that the reaction coefficients (2, 1, and 2 in the preceding example) can be interpreted as molecules, or as moles, or as volumes. This is because Avogadro s law holds for all gases. The number of molecules in 1 mole of a gas is known to be... 

Frequently, the number of active sites is expressed in mole units (the number of active sites divided by the Avogadro number) and thus, turnover frequency is found in s"1 units. For a specific reaction, the turnover frequency depends on the nature of the catalytic active site, the temperature, and the reactants concentration. The above-defined catalytic rate could be described as an active-site level rate. 

The mass fraction Gi of the mass velocity M differs from the mass fraction of the local mixture when diffusion is taking place. Ki is the ordinary reaction rate of chemical kinetics, expressed as mole/unit volume/unit time, which is measured in a static experiment as a function of temperature and composition if the flame is in local thermal equilibrium. If not, this equation serves only as a measure of the nonequilibrium local reaction rate. 

Effect of continuous addition of pyridine to the gas phase on the production-rate of 2 (moles/unit of time) T=140°C feed 1 vol% I 15 vol% 02... 

Now suppose the feed contains a reactant A that irreversibly goes to a product B. Let cin be the concentration of A in the feed and c its concentration both in the tank and the effluent (the assumption of good mixing ensures the last two will be the same), and let the reaction be of the first order so that it proceeds at a rate kc, where k is a constant. The concentrations are in moles/ unit volume and the rate is in moles/(unit volume unit time). A is not conserved as mass was, for the whole point of the reactor is to get A to become B, but we must still be able to account for it. Coming in with the feed stream there are qmcm moles/unit time leaving, unreacted, in the product stream there are qc moles/unit time. When the volume is V, the rate of disappearance of A by reaction is Vkc and the number of moles of A in the vessel is Vc. The rate of change of this last must be the difference between the inflow and the total rate of disappearance of A by outflow and reaction. Thus... 

Temperature units/conversions Periodic table Basic atomic structure Quantum mechanical model Atomic number and isotopes Atoms, molecules, and moles Unit conversions Chemical equations Stoichiometric calculations Week 3 Atmospheric chemistry... 

Expressing the enthalpy balance function i , eq. (25), in mass rather than mole units precludes the necessity of using Holland s (28) "constant composition" formulation. While Hy and Hl depend on the compositions of different phases, the... 

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