Chapter06 - Solutions for Chapter 6 End-of-Chapter Problems...

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ACS Chemistry Chapter 6 suggested solutions 1 Solutions for Chapter 6 End-of-Chapter Problems Problem 6.1. (a) When water is boiled in a teakettle, no chemical reaction occurs. There is a physical change from H 2 O (l) to H 2 O (g) . (b) When boiling water is poured into a bowl containing a package of instant oatmeal and stirred to make a hot cereal breakfast, various components of the cereal dissolve or are re- hydrated (the oatmeal had been previously prepared and the chemical changes that make oatmeal from oat flakes had occurred and then water was removed to produce the instant product). The changes occurring when the product is re-hydrated are probably reasonably classified as physical, not chemical changes. (c) When a glass of a carbonated soft drink is left overnight and tastes “flat” the next morning, CO 2 (g) dissolved in the soft drink as CO 2 (aq) has escaped to the atmosphere. You might think of this as a physical reaction, but it can also be considered a chemical reaction, if some of the dissolved carbon dioxide was present as carbonic acid, (HO) 2 CO (aq) , which is a different chemical species. (d) When a glass of ice cubes and water is left overnight and there are no ice cubes in the water the next morning, no chemical reaction has occurred. The ice cubes melted, H 2 O (s) H 2 O (l) , but no new chemical species formed. Problem 6.2. (a) When a match is dropped on the floor, no chemical change (reaction) occurs. The match is still the match. (b) When a match is struck and used to start a barbeque, several chemical reactions occur. There is a chemical reaction that uses the energy of the friction of the match head to initiate the reaction that lights the match (which continues to burn because the energy released in the burning sustains the reactions). Once the match is burning, the flame is used to start the chemical reaction in the charcoal, propane, or other fuel used in the barbeque. In both cases, the products of the change, carbon dioxide, water, ashes, and so on, are different chemical species than were present in the match and fuel. (c) When a piece of paper is folded to make a paper airplane, no chemical change (reaction) occurs. The paper is still the paper. (d) When a piece of paper is torn into many small pieces to make confetti, you can argue that no chemical change (reaction) has occurred because the little pieces are still paper. On the other hand, tearing the paper apart breaks a large number on intermolecular (not covalent) bonds between the cellulose polymer molecules that make up the paper, so many of these molecules are not making the same bonding interactions they were previously. The distinction between chemical change and physical change is sometimes quite fuzzy and probably not worth making. Problem 6.3. (a) When an acorn buried and forgotten by a squirrel grows into an oak tree, a very large number of chemical reactions have occurred. Many compounds not originally present in the acorn are now present in the oak tree. Other compounds that were originally present in the acorn
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This note was uploaded on 02/23/2012 for the course CHEM AP taught by Professor Hx during the Fall '11 term at Manitoba.

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Chapter06 - Solutions for Chapter 6 End-of-Chapter Problems...

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