Roadmap problem

Over the years, we have seen numerous students throw up their hands when faced with a roadmap problem. Indeed, many students simply skip the roadmap problems on their exams. That s a good way to lose a significant number of points and unnecessarily lower your grade. 

Now you get to take a look at number of roadmap problems. Some instructors include spectra on one or more of the compounds in the problem. We limit the amount of spectral data so you can focus on the approach to the solution of roadmap problems. 

A roadmap problem. Organize your given information and work from it, stepwise, toward the answers. 

PROBLEM 14.60 Lies Lies Lies We can think of at least one way (other than the reaction in Problem 14.59) you can put an aldehyde group on a benzene ring with your current knowledge. It is a roundabout process, and so makes a good roadmap problem. Try this one. Provide structures for compounds A-D. 

Having presented the general features of typical batch scheduling problems we introduce a roadmap that describes the main features of current optimization... 

Many Organic Chemistry 11 excims contain problems known as roadmaps that present you with a collection of facts you use to deduce the identities of a number of compounds. 

If you know your reactions and the other rules, roadmaps aren t as difficult as they seem. The secret is to tackle the problem in small pieces, first by reading the problem and making a few notes then continuing with the exam. Come back to the problem later and make a few more notes. Then go to some other pcirt of the exam. Continue cycling from the roadmap to other questions on the exam until you have sufficient notes to attempt to solve the roadmap. 

The National Institute of Standards and Technology (NIST) maintains Web pages of statistical data for testing software. Direct your Web browser to http //chetnistry.brookscole.com/skoogfac/. From the Chapter Resources menu, choose Web Works, and locate the Chapter 6 section. Here you will find a link to the NIST site. Browse the site to see what kinds of data are available for testing. We use two of the NIST data sets in Problems 6-21 and 6-22. Find the software diagnostics site for the Healthcare Standards Roadmap Project. Describe why the project is needed and the NIST approach. 

Present a roadmap of the solution for many problems in early chapters (and in some later ones). The roadmap is a visual summary of the planned steps. Each step is shown by an arrow labeled with information about the conversion factor or operation needed. 

Plan We first write the balanced equation. Because the amounts of two reactants are given, we know this is a limiting-reactant problem. To determine which reactant is limiting, we calculate the mass of N2 formed from each reactant assuming an excess of the other. We convert the grams of each reactant to moles and use the appropriate molar ratio to find the moles of N2 each forms. Whichever yields less N2 is the limiting reactant. Then, we convert this lower number of moles of N2 to mass. The roadmap shows the steps. Solution Writing the balanced equation ... 

Plan We are given the actual yield of SiC (51.4 kg), so we need the theoretical yield to calculate the percent yield. After writing the balanced equation, we convert the given mass of Si02 (100.0 kg) to amount (mol). We use the molar ratio to find the amount of SiC formed and convert that amount to mass (kg) to obtain the theoretical yield [see Sample Problem 3.8(c)]. Then, we use Equation 3.7 to find the percent yield (see the roadmap). 

Problem A buffered solution maintains acidity as a reaction occurs. In living cells, phosphate ions play a key buffering role, so biochemists often study reactions in such solutions. How many grams of solute are in 1.75 L of 0.460 M sodium monohydrogen phosphate Plan We know the solution volume (1.75 L) and molarity (0.460 M), and we need the mass of solute. We use the known quantities to find the amount (mol) of solute and then convert moles to grams with the solute molar mass, as shown in the roadmap. 

Plan This is a limiting-reactant problem because the amounts of two reactants are given. After balancing the equation, we must determine the limiting reactant. The molarity (0.010 M) and volume (0.050 L) of the mercury(II) nitrate solution tell us the moles of one reactant, and the molarity (0.10 M) and volume (0.020 L) of the sodium sulfide solution tell us the moles of the other. Then, as in Sample Problem 3.10, we use the molar ratio to find the moles of HgS that form from each reactant, assuming the other reactant is present in excess. The limiting reactant is the one that forms fewer moles of HgS, which we convert to mass using the HgS molar mass. The roadmap shows the process. 

Problem Hot H2 can reduce copper(II) oxide, forming the pure metal and H2O. What volume of H2 at 765 torr and 225°C is needed to reduce 35.5 g of copper(II) oxide Plan This is a stoichiometry and gas law problem. To find Fh we first need h,. We write and balance the equation. Next, we convert the given mass of CuO (35.5 g) to amount (mol) and use the molar ratio to find moles of H2 needed (stoichiometry portion). Then, we use the ideal gas law to convert moles of H2 to liters (gas law portion). A roadmap is shown, but you are familiar with all the steps. 

Problem-solving roadmaps specific to the problem lead you visually through the calculation steps. 

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