Molecular equations, balancing

Write a balanced equation for the reduction of molecular oxygen by reduced cytochrome e as carried out by complex IV (cytochrome oxidase) of the electron transport pathway. 

To illustrate how a relatively simple equation can be written and balanced, consider a reaction used to launch astronauts into space (Figure 3.4). The reactants are two liquids, hydrazine and dinitrogen tetraoxide, whose molecular formulas are N2H4 and N204, respectively. The products of the reaction are gaseous nitrogen, N2, and water vapor. To write a balanced equation for this reaction, proceed as follows ... 

Reality Check Notice that the concentration of 02, a product in the reaction, appears in the denominator. The rate is inversely proportional to the concentration of molecular oxygen, a feature that you would never have predicted from the balanced equation for the reaction. As the concentration of 02 builds up, the rate slows down. 

In a similar manner, ethanol can be oxidized by the dichromate ion to form a compound called acetaldehyde, CHaCHO. The molecular structure of acetaldehyde, which is similar to that of formaldehyde, is shown at the bottom in Figure 18-6. We see that the molecule is structurally similar to formaldehyde. The methyl group, —CH3, replaces one of the hydrogens of formaldehyde. The balanced equation for the formation of acetaldehyde from ethanol is... 

H. 10 An important role of stratospheric ozone, Os, is to remove damaging ultraviolet radiation from sunlight. One result is the eventual dissociation of gaseous ozone into molecular oxygen gas. Write a balanced equation for the dissociation reaction. 

Fig. 8.4 Information contained in a balanced equation (from M. S. Silberberg, Chemistry The molecular nature of matter and change, 4th ed., McGraw Hill, 2006, p. 106, reproduced with permission of The McGraw-Hill Companies)...

Ammonium nitrate, a colorless Ionic solid used as a fertilizer, explodes when it is heated above 300 °C. The products are three gases molecular nitrogen, molecular oxygen, and steam (water vapor). Write a balanced equation for the explosion of ammonium nitrate. 

To solve a quantitative limiting reactant problem, we identify the limiting reactant by working with amounts in moles and the stoichiometric coefficients from the balanced equation. For the ammonia synthesis, if we start with 84.0 g of molecular nitrogen and 24.2 g of molecular hydrogen, what mass of ammonia can be prepared First, convert from... 

C04-0147. Write the balanced equation and determine the number of moles of water produced when 2.95 mL of pyridine (C5 H5 N, p = 0.982 g/mL) reacts with excess O2 to give water, carbon dioxide, and molecular nitrogen. 

When deriving material balance equations the rate of each component transformation in the reactor obeys the law of mass action. However, as distinct from the reactions with participation of exclusively low molecular weight substances, the... 

A thermal decomposition reaction is a reaction that is activated by heat or high temperatures and that generates simpler (i.e., containing fewer atoms and thus characterized by lower molecular weights) substances from a single complex substance. The overall balanced equation for the thermal decomposition of sodium bicarbonate reveals the simpler substances produced ... 

This is a critical chapter in your study of chemistry. Our goal is to help you master the mole concept. You will learn about balancing equations and the mole/mass relationships (stoichiometry) inherent in these balanced equations. You will learn, given amounts of reactants, how to determine which one limits the amount of product formed. You will also learn how to determine the empirical and molecular formulas of compounds. All of these will depend on the mole concept. Make sure that you can use your calculator correctly. If you are unsure about setting up problems, refer back to Chapter 1 of this book and go through Section 1-4, on using the Unit Conversion Method. Review how to find atomic masses on the periodic table. Practice, Practice, Practice. 

Q Construct a fully balanced equation lor the oxidation of Cm by molecular oxygen, and calculate the standard potential for the... 

Finally, the balance equation for the SMSL looks like Eq. 23-30, except for the reaction term which is not necessarily linear now. Note that Cssc depends also on z (the depth in the lake, not the depth in the sediment column). Every depth zone has its own SMSL, but it is assumed that these layers do not interact with each other. In fact, the distance between them is much too large for lateral molecular diffusion in the sediments to play any role. There is no equation for the particles in the SMSL. Their balance is indirectly included in the preservation factor (3(z). Remember that if total solids are used to describe the solid phase, (3 is about 1, whereas if particulate organic carbon (POC) is used, (3 is smaller than one because part of the POC is degraded in the SMSL. Finally, we get ... 

Some clostridia ferment glutamate to ammonia, carbon dioxide, acetate, butyrate, and molecular hydrogen. Write a balanced equation and compare with Eq. 24-18 and Fig. 24-8. See Hans et al.478... 

H2, Cl2, and Br2 are placed in a flask and heated to 1000 K. (a) What molecular species will be present when the reactions come to equilibrium Neglect atomic species. Consult Table 9.1. (b) Write all the equilibrium reactions that are possible for this system. Neglect reactions that are the reverse of reactions already written and reactions differing from the others only by a multiplicative factor. Also ignore reactions that are nonproductive, i.e., ones in which the reactants and products are identical. Choose balanced equations that have the lowest possible, whole-number... 

Axial dispersion. An axial (longitudinal) dispersion coefficient may be defined by analogy with Boussinesq s concept of eddy viscosity ". Thus both molecular diffusion and eddy diffusion due to local turbulence contribute to the overall dispersion coefficient or effective diffusivity in the direction of flow for the bed of solid. The moles of fluid per unit area and unit time an element of length 8z entering by longitudinal diffusion will be - D L (dY/dz)t, where D L is now the dispersion coefficient in the axial direction and has units ML T- (since the concentration gradient has units NM L ). The amount leaving the element will be -D l (dY/dz)2 + S2. The material balance equation will therefore be ... 

Now that we know how many moles of ethylene we have (0.536 mol), we also know from the balanced equation how many moles of HC1 we need (0.536 mol), and we have to do a mole-to-gram conversion to find the mass of HC1 required. Once again, the conversion is done by calculating the molecular mass of HC1 and using molar mass as a conversion factor ... 

The chemical equation for an elementary reaction is a description of an individual molecular event that involves breaking and/or making chemical bonds. By contrast, the balanced equation for an overall reaction describes only the stoichiometry of the overall process, but provides no information about how the reaction occurs. The equation for the reaction of N02 with CO, for example, does not tell us that the reaction occurs by direct transfer of an oxygen atom from an N02 molecule to a CO molecule. 

Recall from Section 12.2 that the rate law for an overall chemical reaction must be determined experimentally. It can t be deduced from the stoichiometric coefficients in the balanced equation for the overall reaction. By contrast, the rate law for an elementary reaction follows directly from its molecularity because an elementary reaction is an individual molecular event. The concentration of each reactant in an elementary reaction appears in the rate law, with an exponent equal to its coefficient in the chemical equation for the elementary reaction. 

In accordance with the usual process conditions, the initial temperature of the reactive mixture To and the upper cap temperature Tw are constant during filling, and the temperature of the insert Ti equals the ambient temperature (20°C). The model takes into account that during filling the temperature of the insert increases due to heat transfer from the reactive mix. It is assumed that the thermal properties and density of both the reactive mass and the insert are constant. It is reasonable to neglect molecular diffusion, because the coefficient of diffusion is very small 264 therefore, the diffusion term is negligible in comparison with the other terms in the mass balance equation. 

Starting with glucose and molecular hydrogen, the balanced equation is C6H1206 + 12 H2 --------- 6CH4 + 6 H20... 

Just about the only way to determine the nature of the reaction is to perform it empirically (in the laboratory). Even without running the reaction, we can interpret the balanced equation by stating that, if a large number of ammonia and oxygen molecules are mixed, a certain number of nitrogen and water molecules will be formed. At a given instant it is not necessary that the NH3 or O2 is all consumed, but whatever reaction does occur takes place in the molecular (or mole) ratio prescribed by the equation. 

We need the balanced equation and the molecular masses to determine the answer. 

Before passing on to the analysis of gas-phase oxidation with hydrogen peroxide, we must first obtain information about its dissociation. Hydrogen peroxide easily dissociates to water and molecular oxygen, which is the typical feature, very useful in some cases and unwanted in another. H202 can dissociate in different ways, but all of them are described by the general material balance equation as follows ... 

In the formulation of the microscopic balance equations, the molecular nature of matter is ignored and the medium is viewed as a continuum. Specifically, the assumption is made that the mathematical points over which the balance field-equations hold are big enough to be characterized by property values that have been averaged over a large number of molecules, so that from point to point there are no discontinuities. Furthermore, local equilibrium is assumed. That is, although transport processes may be fast and irreversible (dissipative), from the thermodynamics point of view, the assumption is made that, locally, the molecules establish equilibrium very quickly. 

The IAD I(a,t) in a chemical reactor is specially interesting and it does not seem that sufficient attention has been paid to the possibilities offered by this function. For instance, let us consider a semi-batch reactor, and let Q(t) be the feed flowrate of an incompressible fluid. The instantaneous fluid volume is V = /q Q(tf)dtf, from which the IAD is written I(a,t) = Q(t-a)/V. I(a,t) can be used to calculate the chemical conversion in different segregation states. Consider a species of concentration C produced with the rate t. If the mixture is assumed to be well mixed at the molecular scale, one obtains the familiar mass balance equation... 

Use of Saturation. Because of the potential for simplification of the population balance equations, much recent work has concentrated on studying saturation phenomena. First proposed by Piepmeier (9), and elaborated on by Daily (10), saturation in atomic species can lead to complete elimination of the need to know any collisional rates, and in molecular species may provide substantial simplification of the balance equation analysis. 

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