As with anything else chemists classify reactions

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Unformatted text preview: yte to be covalent? 3. Is it possible to have an insoluble electrolyte? What does this imply about the term “insoluble”? Dakota State University Page 60 of 232 Experiment 3: Chemical Reactions General Chemistry I and II Lab Manual Experiment 3: Chemical Reactions Purpose: To gain experience with the various types of possible chemical reactions. Perturb: To agitate or disturb Background: See “Basic Laboratory Procedures”: pipette, graduated cylinder, balance, glowing splint and Bunsen burner Introduction: Chemistry doesn’t get really interesting until we begin talking about how matter interacts with each other and changes; that is, until chemical reactivity. As with anything else, chemists classify reactions into several different categories, as summarized below. Reaction Number of Reactants Addition 2 or more Number of Products 1 Decomposition 1 2 or more Single Replacement Double Replacement 2 2 2 2 Type Symbolic reaction Example A+BàC 4 Fe (s) + 3 O2 (g) à 2 Fe2 O3 (s) AàB+C C6 H12 O6 (s) à 6 C (graphite) + 6 H2 O (g) AB+CàCB+A Cu (s) + 2 AgNO3 (aq) à 2 Ag (s) + Cu(NO3 )2 (aq) AB+CDàAD+CB NaCl (aq) + AgNO3 (aq) à NaNO 3 (aq) + AgCl (s) There are several means by which one can tell if a chemical reaction has occurred. Essentially, we are closely looking for observations to denote that something has happened. They can be obvious, like a color change, evolution of a gas (by “effervescence”, or fizzing), evolution of a smell, or the formation of a precipitate (a solid that forms when two clear solutions are mixed together). However, some of these observations can also be very small, such as evolution or consumption of heat (the container gets hot or cold), or changes in acidity (pH). The oldest trick in the book for testing gas is the “glowing splint” test. Depending on your reactants, there are a variety of gases that can possibly be given off; this simple little test helps to distinguish four of these gases: oxygen, hydrogen, carbon dioxide and nitrogen. You perform it by taking a glowing splint, lighting it on fire, extinguishing the fire such that the splint continues to glow, and using the splint to test the gases coming off from the reaction. One of three things can happen. Dakota State University Page 61 of 232 Experiment 3: Chemical Reactions If the splint… Goes out completely Re- ignites or glows brighter Explodes (in the form of a loud “pop”) General Chemistry I and II Lab Manual The gas is likely to be… Carbon dioxide or nitrogen oxygen hydrogen In writing a chemical reaction, it is important to remember the law of conservation of matter; one cannot create or destroy matter, but it can change form. From Dalton’s Law, we know that we cannot change the subscripts of the chemicals, because that would change what the chemical is. What we can change is the numbers in front of the chemicals in a chemical reaction (the “stoichiometric coefficients); these can be used to balance a chemical reaction (the same number of each type of atom on each side of the reaction). An unbalanced chemical equation:...
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This note was uploaded on 09/18/2012 for the course CHEMISTRY 1010 taught by Professor Kumar during the Fall '11 term at WPI.

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