Coefficients, molar stoichiometric

The stoichiometric coefficients in mass units can be recalculated to molar stoichiometric coefficients and then the reactions become ... 

Equation 11.1 is an atom balance C, could be considered the chemical formula for j and V, the molar stoichiometric coefficient. For reactants, v- is always defined as a negative number and, for products, a positive number. 

In the weighted sums in the equations above for A H°, the terms are formed by multiplying the standard molar enthalpies of formation by the corresponding stoichiometric coefficients or stoichiometric numbers, both of which are simply numbers (without units). As a result, AjH° has units of kj mol. The basis for these equations is shown in Figure 7-21 and is applied in Example 7-11. At this point, you should also recognize that A H° is the enthalpy change per mole of reaction for the following process. 

One molecule (or mole) of propane reacts with five molecules (or moles) of oxygen to produce three molecules (or moles) or carbon dioxide and four molecules (or moles) of water. These numbers are called stoichiometric coefficients (v.) of the reaction and are shown below each reactant and product in the equation. In a stoichiometrically balanced equation, the total number of atoms of each constituent element in the reactants must be the same as that in the products. Thus, there are three atoms of C, eight atoms of H, and ten atoms of O on either side of the equation. This indicates that the compositions expressed in gram-atoms of elements remain unaltered during a chemical reaction. This is a consequence of the principle of conservation of mass applied to an isolated reactive system. It is also true that the combined mass of reactants is always equal to the combined mass of products in a chemical reaction, but the same is not generally valid for the total number of moles. To achieve equality on a molar basis, the sum of the stoichiometric coefficients for the reactants must equal the sum of v. for the products. Definitions of certain terms bearing relevance to reactive systems will follow next. 

To calculate the change in entropy that accompanies a reaction, we need to know the molar entropies of all the substances taking part then we calculate the difference between the entropies of the products and those of the reactants. More specifically, the standard reaction entropy, AS°, is the difference between the standard molar entropies of the products and those of the reactants, taking into account their stoichiometric coefficients ... 

The value of AG at a particular stage of the reaction is the difference in the molar Gibbs free energies of the products and the reactants at the partial pressures or concentrations that they have at that stage, weighted by the stoichiometric coefficients interpreted as amounts in moles ... 

To keep the units straight, we need to use the molar convention for this calculation and to use the stoichiometric coefficients in reaction E as pure numbers. To find an expression for AGr, we substitute F q. 4 for each substance into Eq. 3a. For example, for the general reaction E,... 

Gibbs free energy of reaction The difference in molar Gibbs free energies of the products and reactants, weighted by the stoichiometric coefficients in the chemical equation. 

In the model equations, A represents the cross sectional area of reactor, a is the mole fraction of combustor fuel gas, C is the molar concentration of component gas, Cp the heat capacity of insulation and F is the molar flow rate of feed. The AH denotes the heat of reaction, L is the reactor length, P is the reactor pressure, R is the gas constant, T represents the temperature of gas, U is the overall heat transfer coefficient, v represents velocity of gas, W is the reactor width, and z denotes the reactor distance from the inlet. The Greek letters, e is the void fraction of catalyst bed, p the molar density of gas, and rj is the stoichiometric coefficient of reaction. The subscript, c, cat, r, b and a represent the combustor, catalyst, reformer, the insulation, and ambient, respectively. The obtained PDE model is solved using Finite Difference Method (FDM). 

Entropy changes are important in every process, but chemists are particularly interested in the effects of entropy on chemical reactions. If a reaction occurs under standard conditions, its entropy change can be calculated from absolute entropies using the same reasoning used to calculate reaction enthalpies from standard enthalpies of formation. The products of the reaction have molar entropies, and so do the reactants. The total entropy of the products is the sum of the molar entropies of the products multiplied by their stoichiometric coefficients in the balanced chemical equation. The total entropy of the reactants is a similar sum for the reactants. Equation... 

Each calculation uses the stoichiometric coefficients from the balanced chemical equation and the molar mass of the reactant. 

The molar ratios given by the stoichiometric coefficients in the balanced chemical equations are used in the solution. 

The reaction is C4H6(A) + C2H4(B) -> CfiH10(C). Since the molar ratio of A to B in the feed is 1 1, and the ratio of the stoichiometric coefficients is also 1 1, cA = cB throughout the reaction. Combining the material-balance equation (15.2-2) with the rate law, we obtain... 

Figure 19 shows the stoichiometric coefficient y versus time. The y-coefficient is the molar ratio between the amount of hydrogen in the conversion gas and the amount of carbon in the conversion gas. In this particular selection of y-graphs the dynamic ranges for the different wood fuels during a batch are fuel wood 3 0, wood pellets 2.6 0, and wood chips 2.4 0. These dynamic ranges are quite representative of the whole range of volume fluxes tested. 

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