Design an Experiment

Suppose you are given a bottle of sulfur, which is a yellow solid, a cylinder of O2, a transparent reaction vessel that can be evacuated and sealed so that only sulfur, oxygen and the product(s) of the reaction between the two are present, an analytical balance so that you can determine the masses of the reactants and/or products, and a furnace that can be used to heat the reaction vessel to 200 °C where the two elements react, (a) If you start with 0.10 mol of sulfur in the reaction 

Water covers nearly two-thirds of our planet, and this simple substance has been the key to much of Earth s evolutionary history. Life almost certainly originated in water, and the need for water by all forms of life has helped determine diverse biological structures. 

Scientists had studied the chemistry of the ocean for decades before discovering deep sea vents in 1979. The chemical reactions that occur near deep sea vents are, as you might imagine, difficult to study nonetheless, chemists working in deep-sea submers-ibles equipped with sampling arms are helping us learn what happens in these hot, toxic waters. 

One reaction that occurs in deep sea vents is the conversion of FeS into FeS2  

A solution in which water is the dissolving medium is called rm aqueous solution. In this chapter we examine chemical reactions that take place in aqueous solutions. In addition, we extend the concepts of stoichiometry learned in Chapter 3 by considering how solution concentrations are expressed and used. Although the reactions we will discuss in this chapter are relatively simple, they form the basis for imderstanding very complex reaction cycles in biology, geology, and oceanography. 

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Designing an experiment is like designing a product. Every product serves a purpose so should every experiment. This purpose must be clearly defined at the outset. It may, for example, be to optimize a process, to estimate the probabiUty that a component operates properly under a given stress for a specified number of years, to evaluate the relative effects on product performance of different sources of manufacturing and end use variabiUty, or to determine whether a new process is superior to an existing one. An understanding of this purpose is important in developing an appropriate experimental plan. 

Such programs generally concentrate on the technical parts of designing an experiment, and provide limited guidance on the important, softer aspects of experimental design stressed in this article. Also, most computer routines do not allow one to handle various advanced concepts that arise frequently in practice, eg, spHt plot and nested situations, discussed in the books in the bibhography. In fact, some of the most successful experiments do not involve standard canned plans, but are tailored to fit the problem at hand. 

The current study was limited by viscosity due to mechanical limitation in reactor design. An experiment... 

American physicist Robert A. Millikan and his student Harvey Fletcher designed an experiment to determine the charge on the electron. As shown in Figure 2-14. the apparatus was a chamber containing two electrical plates. An atomizer sprayed a mist of oil droplets into the chamber, where the droplets drifted through a hole in the top plate. A telescope allowed the experimenters to measure how fast the droplets moved downward under the force of gravity. The mass of each droplet could then be calculated from its rate of downward motion. 

Designing an Experiment/ldentifying Variables How could you have made the bananas ripen even faster ... 

Designing an Experiment/ldentifying Variables What was the function of the control test tube ... 

Simon That is what we are planning to do. We need to show that all stem cells express CEV3, and that all C-LT/bbexpressing cells are stem cells. We are designing an experiment to test this. 

One of the first decisions to be made when designing an experiment is the method of detection to be used with a particular solute. If radiolabeled material is available, a simple method of analysis is to count the radiolabel appearing in the receiver compartment as a function of time. While convenient, this can be a dangerous practice. Depending upon the type of radioisotope, its position in the molecule, and its specific activity, radiolabeled compounds can be subject to a variety of chemical and solution-catalyzed degradation pathways. If the stock solution contains a significant amount of radioactive impurities or generates them as a result of solution instability, then the possibility for preferential transport of... 

Since phosphorus and protons are both abundant spin-1/ nuclei, it is simple to design an experiment in which we correlate protons and phosphorus rather than protons with themselves. The result of this experiment, a P,H correlation, is shown in Fig. 26. Again we have the 2D spectrum in the form of a central rectangle and two (previously recorded) ID spectra parallel to the axes. One is the proton spectrum, the other the phosphorus spectrum. The latter of course consists of a single line, and in the 2D spectrum we do not need to look for a diagonal as there cannot be one. 

You want to find the wind drag on a new automobile design at various speeds. To do this, you test a 1/30 scale model of the car in the lab. You must design an experiment whereby the drag force measured in the lab can be scaled up directly to find the force on the full-scale car at a given speed. 

To prove your theory, you need to design an experiment that will... 

Experiment 20 Designing an Experiment Determining the Wavelength at which a Beer s Law Plot Becomes Nonlinear... 

Experiment 43 Designing an Experiment for Determining Ethanol in Cough Medicine or Other Pharamaceutical Preparation... 

Design an experiment based on your experience in Experiment 42 to determine the alcohol content in cough medicine or other pharmaceutical preparation. Ask your instructor to approve your approach before beginning the work. 

Experiment 48 Designing an Experiment for Determining Caffeine in Coffee and Tea... 

Using Experiment 47 as a base, design an experiment for determining the caffeine in various coffees and... 

Nilsson et al. designed an experiment to test the ability of a polymer to directly detect conformational changes within peptide/protein structure [27]. Using the zwitterionic polythiophene derivative, POWT, they succeeded in detecting the distinct conformations of synthetic peptides. The mechanism was concluded to be based on the polymer side chains charged interactions and hydrogen bonding with the proteins. 

Use the above procedure to design an experiment in which you can observe the effect of temperature on the rate of evaporation of ethanol. Your teacher will provide a sample of warm ethanol. Record your observations. 

Designing an Experiment Write a brief statement of how you would set up an experiment to test your hypothesis. 

Designing an Experiment How would you test your hypothesis ... 

Perhaps by using partly deuterated feeds one can design an experiment to find prooffor the chain running mechanism in the reaction below. 

The first decision to be made in designing an experiment to measure the motional properties of membrane lipids concerns the type of probe molecule. Too often, this choice is made from the point of view of convenience or tradition rather than suitability, although there is now a considerable range of suitable fluorophores from which to choose. The second consideration is the type of measurement to be made. The most detailed and complete motional information is obtained from a time-resolved fluorescence anisotropy measurement which is able to separate the structural or orientational aspects from the dynamic aspects of fluorophore motion. Steady-state anisotropy measurements, which are much easier to perform, provide a more limited physical parameter relating to both of these aspects. 

The type of bonding in a substance depends upon the kinds of atoms it contains and the forces of attraction between those atoms. If you know the physical properties of a substance, you can often predict the type of bonding in the substance. Table 4.5 summarizes the types of forces of attraction and the physical properties of solids with different types of bonding discussed in this section. In Investigation 4-B, you will design an experiment in which you predict the type of bonding in various substances, then test your prediction. 

This investigation challenges you to design an experiment to observe and analyze the physical properties of different substances, and to determine the types of bonding present. 

Design an experiment to test your predictions. Ensure that you have adequately addressed all possible safety considerations. Obtain approval from your teacher before you begin your investigation. 

O Concentrated sulfuric acid can be diluted by adding it to water. The reaction is extremely exothermic. In this question, you will design an experiment to measure the enthalpy change (in kj/mol) for the dilution of concentrated sulfuric acid. Assume that you have access to any equipment in your school s chemistry laboratory. Do not carry out this experiment. 

O O Design an experiment to determine the efficiency of a laboratory burner. You will first need to decide how to define the efficiency, and you will also need to find out what fuel your burner uses. Include a complete procedure and safety precautions. 

Design an experiment to determine Kgj, for lead(II) chloride, PbCl2, using the following reaction. 

Design an experiment to determine Kgp for lead(II) iodide, Pbh, using the reaction below. 

O Design an experiment that uses the technique of downward... 

What can we say a priori about the rates of individual steps We find immediately that there is very little relation between the rates for the various steps of a reaction. In fact, normally the rates of the different steps of a reaction vary over a wide range. This situation enables us to make an important conelusion. The rate of one step of a reaction is often so much slower than the rates of the other steps that this one step is the rate-determining step. As a consequence, one can frequently design an experiment so that the observed rate is actually the rate of that one step. 

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