Worked Example No

If a mixture of lO.Og of A1 and 50.0 g of Fe203 react with each other to produce AI2O3 and Fe, how many grams of iron are produced  

2 moles of A1 reacts completely with 1 mole of Fe203 to produce 2 moles of Fe 

50g of Fe203 = 50/159.6 moles of Fe203 = 0.313 moles Answer 0.313 moles of Fe203 are present. 

1 mole Fe203 = 2 moles Al 0.313 moles Fe203 = 0.626 moles Al 

Answer 0.626 moles of A1 are required, but as there are only 0.37 moles of A1 present therefore A1 is the limiting reagent. 

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Calculations of hydrogen removal at ambient temperature are of little practical value for thick sections, and this statement is borne out by the results of Worked Example No.l, later in this chapter. 

Detail of Worked Example no. 1 (a) actual detail, (b) simplification to plane plate geometry, and (c) simplification to cylindrical geometry dimensions in mm. 

Table 5.4 Estimates of the percentage of the original hydrogen remaining at the centre of the weld after various heat treatments for Worked Example No. 1. ...

Table 5.5 Estimation of the percentage of the original hydrogen removed from individual beads of a multirun weld during the interpass period Worked Example No. 2...

The two-layer model is being progressively updated as fresh experimental results and correlations become available. The most satisfactory starting-point for anyone wishing to use the model to calculate pressure gradients for flow of solids-liquid mixtures in a pipeline is the text of SHOOK and Roc.o(52) which includes a worked example. However, there are many pitfalls to be avoided in this area, and there is no substitute for pracucal experience gained by working in the field. 

Harano and colleagues [48] found that the reactivity of the Diels-Alder reaction of cyclopentadienones with unactivated olefins is enhanced in phenolic solvents. Scheme 6.28 gives some examples of the cycloadditions of 2,5-bis-(methoxycar-bonyl)-3,4-diphenylcyclopentadienone 45 with styrene and cyclohexene in p-chlorophenol (PCP). Notice the result of the cycloaddition of cyclohexene which is known to be a very unreactive dienophile in PCP at 80 °C the reaction works, while no Diels-Alder adduct was obtained in benzene. PCP also favors the decarbonylation of the adduct, generating a new conjugated dienic system, and therefore a subsequent Diels-Alder reaction is possible. Thus, the thermolysis at 170 °C for 10 h of Diels-Alder adduct 47, which comes from the cycloaddition of 45 with 1,5-octadiene 46 (Scheme 6.29), gives the multiple Diels-Alder adduct 49 via decarbonylated adduct 48. In PCP, the reaction occurs at a temperature about 50 °C lower than when performed without solvent, and product 49 is obtained by a one-pot procedure in good yield. 

Mitigation measures can also be passive safeguards, meaning that they require no human intervention and no engineered sensing and actuation system to work. Examples of passive mitigation measures are secondary containment systems, blast-resistant and fire-resistant structures, insulated or low-heat-capacity spill surfaces to reduce the rate of evaporation, and an increased distance between the hazardous materials and energies and the sensitive receptors. 

A medicine or skin lotion is often described as pH neutral as though it was obviously a good thing. A solution is defined as neutral if it contains neither an excess of solvated protons nor an excess of hydroxide ions. Equation (6.4) tells us the autoprotolysis constant Kw of super-pure water (water containing no additional solute) is 10-14 (moldm-3)2. Furthermore, we saw in Worked Example 6.1 how the concentration of the solvated protons was 10-7 mol dm-3 at 298 K. 

Figure 8.1 shows such a graph. The gradient of the graph is 1.09 x 106 dm3 s-1 (which is the same value as that cited in Worked Example 8.1). Notice how the intercept is zero, which confirms the obvious result that the rate of reaction is zero (i.e. no reaction can occur) when no reactants are present. 

Worked Example 5.3. A coulometric experiment is performed to determine the faradaic efficiency of an electrode. The faradaic electrode reaction, Sn (aq) -f 2e (Pt) Sn(s) , occurs with no electrolytic side reactions. The electrode has an area of 9.8 cm and the double-layer is charged with 20 mC cm . What is the faradaic efficiency when (i) a total charge of 1.0 C is passed, and (ii) a total charge of 320 C is passed ... 

This present book is no more than an introduction to electroanalytical chemistry. It is not a textbook, but is intended for those wanting to learn at a distance, or in the absence of a suitable tutor. Accordingly, the approach taken is that of a series of tutorial questions and worked examples, interspersed with questions for students to attempt in their own time. In no way is this meant to be a definitive text students who have mastered these topics are recommended to consult the books and articles listed in the Bibliography at the end. 

The move structure for the Outcomes and Impacts section of the Project Description is shown in hgure 14.1. The hrst two moves summarize the proposed work by highlighting expected achievements. Typically, no new information is provided in these moves rather, their purpose is to summarize deliverables or tangible accomplishments that will result from the work. Examples include the delivery of a more efficient synthesis, an improved analytical procedure, or a novel application of an instrument. Deliverables also include the dissemination of Endings through conference presentations, publications, and patents, allowing the larger scientific community to learn about your work. 

At present, there is no comprehensive gujdance on this topic However, it has been the subject "of much, research, particularly by the Design Institute for Emergency Relief Systems (DIERS) of the American Institute of Chemical Engineers (AlChE). As a result, the DIERS Project Manual[1] (a, record of the DIERS research) and a considerable number of papers have been published. This Workbook summarises the main hand calculation methods (which do not.need. the use of a computer) available as a result of this work and their limits of applicability. A number of worked examples are given to. help the reader understand their application. The experimental information required to size an emergency relief, system properly is also discussed.. ... 

While a great deal of research has been done on condensations of oxometalates in aqueous solutions, there has been little such work in the field of thiometalates. The condensation reactions subsequent to protonation of thiometalate ions take place at lower pH than those of the oxoanions, since the proton affinity of S is appreciably lower than that of O. Investigation of condensation behavior of thiometalate ions is more difficult, since various complex decomposition processes are also involved. For example, no definite condensation product has yet been isolated from an aqueous solution containing MoS2-. 

Worked Example 3.18 shows a combustion analysis when the sample contains oxygen in addition to carbon and hydrogen. Because oxygen yields no combustion products, its presence in a molecule can t be directly detected by this method. Rather, the presence of oxygen must be inferred by subtracting the calculated masses of C and H from the total mass of the sample. 

When the mass m of an object is relatively large, as is true in daily life, then both Ax and Av in the Heisenberg relationship can be very small. We therefore have no apparent problem in measuring both position and velocity for visible objects. The problem arises only on the atomic scale. Worked Example 5.6 gives a sample calculation. 

Step 5. If no unassigned electrons remain after step 3 but the central atom does not yet have an octet, use one or more lone pairs of electrons from a neighboring atom to form a multiple bond (either double or triple). Oxygen, carbon, nitrogen, and sulfur often form multiple bonds. Worked Example 7.7 shows how to deal with such a case. 

As noted, the weir crest 4, is calculated on an equivalent clear-liquid basis. A more realistic approach is to recognize that in general a froth or spray flows over the outlet weir (settling can occur upstream of the weir if a large calming zone with no dispersers is used). Bennett et al. [AIChE J., 29, 434 (1983)] allowed for froth overflow in a comprehensive study of pressure drop across sieve trays their correlation for residual pressure drop h L in Eq. (14-100) is presented in detail in the previous (seventh) edition of this handbook, including a worked example. Although more difficult to use, the method of Bennett et al. was recommended when determination of pressure drop is of critical importance. 

The examples presented in this work by no means cover the subject of the C-H bond activation on a spectrum of catalytic media. Interaction of methane with the small clusters discussed here obviously cannot pretend to fully mimic catalytic centers in reality. Nevertheless, they seem to justify drawing generalized conclusions regarding the mechanism of catalytic activation in terms of electron withdrawal or donation to the interacting hydrocarbon molecule. A variety of properties contribute consequently to the emerging scheme (electronic density redistribution, geometry evolution in critical points, energetical factors, vibrational analyses) which substantially increases credibility of the conclusions. 

Although some such syntheses are quite useful, most appear to have been observed in the course of other work and their mechanisms remain unproven. Accordingly, in presenting the following examples, no attempt will be made here to correlate substrate/synthon atoms with ring atoms in the final product. 

One group of NADH oxidants, which does not fit the proposed reaction scheme in Fig. 2.4 are the metal complexes. Examples of this type include nickel hexacyanoferrate deposited on porous nickel electrodes [29], gold electrodes modified with cobalt hexacyanoferrate films [30] and adsorbed l,10-phenanthroline-5,6-dione complexes of ruthenium and osmium [31]. It is unclear how these systems work and no mechanism has been proposed to date. It may be worth noting that dihydronicotinamide groups have been shown to reduce aldehydes in a non-enzymatic reaction when the reaction is catalysed by zinc, a metal ion [15]. In a reaction between 1,10-phenanthroline-2-carboxaldehyde and N-propyl-l,4-dihydronicotinamide, no reaction was seen in the absence of zinc but when added to the system, the aldehyde was reduced and the nicotinamide was oxidised. This implies that either coordination to, or close proximity of, the metal ion activates... 

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