Stoichiometry of Gaseous Reactions

As pointed out in Chapter 3, a balanced equation can be used to relate moles or grams of substances taking part in a reaction. Where gases are involved, these relations can be ex tended to include volumes. To do this, we use the ideal gas law and the conversion factor approach described in Chapter 3. 

Click Coached Problems for a self-study module on stoichiometry of gases. 

Hydrogen peroxide, H202, is a common bleaching agent. It decomposes quickly to water and oxygen gas at high temperatures. 

Sodium bicarbonate (baking soda) is widely used to absorb odors inside refrigerators. When acid is added to baking soda, the following reaction occurs  

Strategy Do not forget to convert temperature and pressure to the appropriate units. 

Find the mass of H2O2. Note that you cannot directly use the volume of H2O2 to calculate the volume of O2 because H2O2 is NOT a gas. 

Q If NaHCOj is in excess, what volume of HCl is required to produce 2.65 L of CO2 o What volume of CO2 is produced when all the NaHCOs is made to react with 50.0 mL of HCl  

H is the reacting species. FICl is the parent compound, stoichiometric ratio 1 H /1 CO2 

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Chapter 5 groups stoichiometry of gaseous reactions with other rearrangements of the ideal gas law. 

Gaseous mixtures of CI2O and NH3 explode violently the overall stoichiometry of the reaction can be represented as... 

Titration. This technique provides a convenient method for following the stoichiometry of a reaction between a gas and a solution or pure liquid. Also, similar techniques can be applied to the study of gas-liquid equilibria and gas-solid equilibria. In a tensimetric titration, measured amounts of a gaseous reactant are added to a solution. After each addition a pressure measurement is made. A plot of these pressures versus the moles of added gas is then inspected for the break-point, which represents the stoichiometry of interaction (Fig. 9.4). 

To determine the stoichiometry of the reaction, count the number of reactant A2 molecules and B atoms and the number of product AB molecules. To predict the sign of the entropy change, see if the reaction increases or decreases the number of gaseous particles. 

We next develop the mass balance equations for the gaseous reactant (oxygen) and the product (sulfur dioxide). The gas flow in the reactor is assumed to be in plug flow and hence the concentration of these gases will depend only on the height H, in the bed above the distributor plate. The rate of consumption of oxygen by reactions 1, 2 and 3 can be obtained from Eqs. 43 and 80 and the stoichiometry of these reactions. We will first examine Eq. 43 which may be rewritten as follows after appropriate substitutions. 

Although there are reports involving the use of hydrogen alone,161 the surface composition of supported Pt-Ru bimetallic catalysts are more commonly measured using a selective titration method.162-164 The titration stoichiometry of the reaction between chemisorbed oxygen and gaseous CO is different for the two metals the ratio of surface metal/02/C0/C02 is 1/0.5/2/1 for Pt and 1/1/1/0.3 on Ru.164 These ratios are independent of surface composition and the concentration of Ru and Pt in the surface can be calculated from the equations ... 

Clearly, if the concentrations or pressures of all the components of a reaction are known, then the value of K can be found by simple substitution. Observing individual concentrations or partial pressures directly may be not always be practical, however. If one of the components is colored, the extent to which it absorbs light of an appropriate wavelength may serve as an index of its concentration. Pressure measurements are ordinarily able to measure only the total pressure of a gaseous mixture, so if two or more gaseous products are present in the equilibrium mixture, the partial pressure of one may need to be inferred from that of the other, taking into account the stoichiometry of the reaction. 

There are three distinct phases in this equilibrium, a solid ferric sulfate phase, a solid ferric oxide phase, and a gaseous phase. Therefore, P = 3. As with the H2O dissociation, there are only two independent components in this equilibrium. (The amount of the third component can be determined from the stoichiometry of the reaction.) Therefore C = 2. Using the Gibbs phase rule,... 

The process includes a total of 12 unit procedures. The first reaction step (procedure P-1) involves the chlorination of quinaldine. Quinaldine is dissolved in carbon tetrachloride (CCU) and reacts with gaseous CI2 to form chloroquinaldine. The conversion of the reaction is around 98% (based on amount of quanaldine fed). The generated HCl is then neutralized using Na CO. The stoichiometry of these reactions follows ... 

Stoichiometry of surface reactions between organometallic complexes and surfaces should be determined, inter alia, by quantitative analysis of gaseous products, surface metal concentration, and quantitative extraction of surface complexes. 

The radiation chemistry has been mainly discussed in terms of degradation reactions (as above) involving the loss of gaseous products and the irreversible change of the stoichiometry [203]. However, more recent results showed that polymers irradiated with radiation deposit-... 

When a solid particle of species B reacts with a gaseous species A to form only gaseous products, the solid can disappear by developing internal porosity, while maintaining its macroscopic shape. An example is the reaction of carbon with water vapor to produce activated carbon the intrinsic rate depends upon the development of sites for the reaction (see Section 9.3). Alternatively, the solid can disappear only from the surface so that the particle progressively shrinks as it reacts and eventually disappears on complete reaction (/B =1). An example is the combustion of carbon in air or oxygen (reaction (E) in Section 9.1.1). In this section, we consider this case, and use reaction 9.1-2 to represent the stoichiometry of a general reaction of this type. 

On the basis of these data, the following mechanism for reduction by hydrogen can be suggested. H2, activated over the Pt sites according to the Pt-catalyzed pathway discussed previously, reduces the stored nitrates directly to ammonia or, more likely, induces the decomposition of nitrates to gaseous NO, which are then reduced by H2 to NH3 over the Pt sites [overall reaction (13.47)]. Once ammonia has been formed, it can react with adsorbed nitrates and this reaction is very selective towards nitrogen. It is worth noting that the reaction of ammonia with NOx obeys the stoichiometry of reaction (13.49), which is different from that of the well-known NH3-NO SCR reaction because it implies the participation of nitrates. 

Most combustion processes are chain-branching, but other examples of chain-branching reactions are also found in industrial systems. Chain-branching reaction systems are potentially explosive, and for this reason great care must be taken to avoid safety hazards in dealing with them. The explosion behavior of gaseous fuels as a function of stoichiometry, temperature, and pressure has been an important research area [241]. Experimental data are typically obtained in a batch reactor, a spherical vessel immersed in a liquid bath maintained at a specific temperature. The desire to understand the explosion behavior of various... 

A detailed study of the oxidation of alkenes by O on MgO at 300 K indicated a stoichiometry of one alkene reacted for each O ion (114). With all three alkenes, the initial reaction appears to be the abstraction of a hydrogen atom by the O ion in line with the gas-phase data (100). The reaction of ethylene and propylene with O" gave no gaseous products at 25°C, but heating the sample above 450°C gave mainly methane. Reaction of 1-butene with O gives butadiene as the main product on thermal desorption, and the formation of alkoxide ions was proposed as the intermediate step. The reaction of ethylene is assumed to go through the intermediate H2C=C HO which reacts further with surface oxide ions to form carboxylate ions in Eq. (23),... 

Gases that are involved in chemical reactions obey the same laws of stoichiometry that apply to substances in any other state, as described in Chapters 8 and 10. Therefore, the ideal gas law can be used to calculate the quantities of gaseous substances involved in a reaction and then those results used to find the quantities of other substances. Figure 12.10 presents the conversions allowed by the ideal gas law (with green backgrounds), in addition to those originally shown in earlier figures. 

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