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Collection: The Chem Collective
(Complete Item Description)
- Abstract: You can access the problems below via the Load Homework dialogue in the File menu of the Virtual Lab. They have been organized by concept and ranked by difficulty (A ranking of 1 denotes an easier problem; 5 is more challenging). Word files for these problems are provided so that you may edit and distribute the assignments in your classroom. The following types of problems can be found:Strong and Weak Acid and Base Problems, Determination of the pH Scale by the Method of Successive Dilutions, Standardization of NaOH: Acid Base Titration, Determining the pKa and concentration ratio of a protein in solution, Unknown Acid and Base problem, Creating a Buffer Solution, DNA - Dye Binding: Equilibrium and Buffer Solutions.
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- Abstract: The molecular weight is the mass of one mole of a substance. Usually, the units used for this are grams per mole. In this movie, we show how to calculate the molecular weight of a substance from the atomic weights given on the periodic table. On another page, we use the molecular weight to convert between the macroscopic scale (grams of a substance) and the microscopic scale (number of molecules of that substance).
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- Abstract: You can access the problems below via the Load Homework dialogue in the File menu of the Virtual Lab. They have been organized by concept and ranked by difficulty (A ranking of 1 denotes an easier problem; 5 is more challenging). Word files for these problems are provided so that you may edit and distribute the assignments in your classroom. The following types of problems can be found: Cobalt Chlorid and LeChatlier's Principle and DNA Binding.
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- Abstract: For certain mixtures, reactions can be used to determine the relative composition of a mixture. This is illustrated in the following video.
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- Abstract: Composition stoichiometry allows us to determine the number of atoms present in a collection of molecules, as shown in the following video.
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- Abstract: When you work in a laboratory, chances are you are starting off with a concentrated stock solution. Being able to create solutions of varying concentration from this is a useful skill. Solutions with known concentrations are often called "standard solutions." You can learn about the concept of dilution and how to use dilution to make a standard solution from a stockroom solution in the following video.
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- Abstract: Dimensional analysis allows us to change the units used to express a value. For instance, it allows us to convert between volume expressed in liters and volume expressed in gallons. The following video gives a brief overview of dimensional analysis, including conversion between the amount of a substance expressed in "number of molecules" and the amount of a substance expressed in "moles of molecules."
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- Abstract: On another page, we discuss how to obtain the empirical formula from a given molecular formula. Here, we consider how to obtain the empirical formula from an elemental analysis of a sample. Remember that comparing the empirical formula obtained from an elemental analysis with that from a molecular formula tells us if the sample is consistent with the molecular formula.
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- Abstract: Elemental analysis is a useful qualitative analysis technique since it allows us to check if a sample is consistent with a given molecular formula. For instance, suppose we believe our sample is benzene (C6H6). We can compare the following:The empirical formula (CH) obtained from the molecular formula of benzene (C6H6); The empirical formula obtained from a elemental analysis of the sample. If the two empirical formulae do not agree, then the sample is not benzene. If the formulae agree, then our sample may be benzene. (Remember that more than one molecule can have the sample empirical formula. For instance, both benzene (C6H6) and acetylene (C2H2) have the empirical formula CH, so a sample whose elemental analysis yields CH as an empirical formula could be benzene, acetylene, or some other molecule with a 1:1 ratio between C and H.)
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- Abstract: We are now ready to pull everything we know about reaction stoichiometry together, and answer the question: Given some initial amount of reactants, what should be present after a chemical reaction goes to completion? The procedure for answering this question is often called the "limiting reagent problem." You'll see why this name is appropriate in the following video.
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- Abstract: You and a friend are hiking the Appalachian Trail when a storm comes through. You stop to eat, but find that all available firewood is too wet to start a fire. From your Chem 106 class, you remember that heat is given off by some chemical reactions; if you could mix two solutions together to produce an exothermic reaction, you might be able to cook the food you brought along for the hike. Luckily, being the dedicated chemist that you are, you never go anywhere without taking along a couple chemical solutions called X and Y just for times like this. The Virtual Lab contains solutions of compounds X and Y of various concentrations.
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- Abstract: This activity is set in a research group that is developing an antivenom for spider bites. In the opening scene, Nelson Pogline, a talented graduate student, dies unexpectedly at a university reception. As a detective, you must use chemistry concepts to determine if this was murder and if so, solve the case. You can interview suspects using Quicktime movies, investigate the crime scene for clues with Quicktime Virtual Reality images, and analyze the evidence from the crime lab. This activity requires basic knowledge of formula weight, stoichiometry, and the scientific method. Additional concepts that are discussed include molecular recognition, limiting reagents, and mass spectrometry.
- Subject:
Science and Technology
- Grade Level:
Secondary, Post-secondary
- Collection:
The Chem Collective
(Complete Item Description)
- Abstract: You can access the problems below via the Load Homework dialogue in the File menu of the Virtual Lab. They have been organized by concept and ranked by difficulty (A ranking of 1 denotes an easier problem; 5 is more challenging). Word files for these problems are provided so that you may edit and distribute the assignments in your classroom. The following types of problems can be found: dilution problems, Sucrose problem, Making Solutions from Solids, Metal Density problem, Liquid Density problem, Alcohol Density problem.
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- Abstract: You probably remember the mole from high school chemistry, but do you remember why it is useful to chemists? The goal of the following video is to give the "big picture" of the mole and its applications; information on how to use the mole in calculations can be found in another tutorial. Throughout this course, we will use the term "molecular weight" to refer to the mass of a mole of a substance (for instance, the molecular weight of oxygen (O2) is 32 g/mol). Recent textbooks refer to this as "molar mass" to emphasize (i) that this term refers to the mass, not the weight, of substance, and (ii) that the quantity refers to a mole of a substance, not a single molecule. "Molecular weight" may be less precise, but it remains the term that most practicing chemists use in the laboratory. For this reason, we continue to use "molecular weight" in this course.
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- Abstract: During the first kinetics lecture, we traced the efforts of atmospheric chemists to explain the depletion of ozone in the upper atmosphere. (The powerpoint slides have been posted on Blackboard for your review.) U2 spy planes gathered much of the initial data that linked ClO in the stratosphere to the ozone depletion. The data collected during these flights showed the concentrations of various chemical species in the stratosphere, but did not measure how fast the processes were occurring. To determine the kinetics (rates) of ozone depletion reactions, chemists perform controlled laboratory studies. In this homework, we will interpret data obtained from such laboratory experiments to study the ozone depletion reaction.
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- Abstract: A reference and instruction for scientists of all levels. What chemistry software package would be complete without a periodic table? The actual use of this applet in the classroom is quite simple. Simply click on the desired element and data as well as a graphical plot of electron configurations will be displayed. This particular version shows the electronic configuration of the element in the panel on the right. Future versions of this applet will show relative atomic sizes, electronegativities and other periodic trends, as well as extensive atomic data.
- Subject:
Science and Technology
- Grade Level:
Secondary, Post-secondary
- Collection:
The Chem Collective
(Complete Item Description)
- Abstract: In another tutorial, we considered the amount of reactant consumed by a chemical reaction. Here, we'll consider the amount of product formed by a reaction.
(Complete Item Description)
- Abstract: You can access the problems below via the Load Homework dialogue in the File menu of the Virtual Lab. They have been organized by concept and ranked by difficulty (A ranking of 1 denotes an easier problem; 5 is more challenging). Word files for these problems are provided so that you may edit and distribute the assignments in your classroom. The following types of problems can be found:Unknown Silver Chloride and Gravimetric Determination of Arsenic.
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