Chem1201PReviewCh3 - Chemistry 1201 Review/Preview Chapter...

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Chemistry 1201 Review/Preview Chapter Three Review Guide Dr. Saundra McGuire Spring 2007 Stoichiometry: Calculations with Chemical Formulas and Equations I. Balancing Chemical Equations: A. Memorize the diatomic elements: hydrogen, oxygen, fluorine, chlorine, bromine, iodine B. Write the correct chemical formula for all compounds using the charge criss-cross method discussed in Chem 1201 Review/Preview session. C. Make the number of each kind of element the same on both sides of the equation by putting in the correct coefficients. Never change the subscripts to balance an equation. See section 3.1 in the text for more information and examples. II. Simple Patterns of Chemical Reactivity T hree simple types of reactions are frequently encountered in this chapter: combination (or synthesis) reactions, decomposition reactions, and combustion reactions. An example of each type is shown below. 1. Combination (or synthesis) reactions are those in which two or more substances combine to form a larger substance. The general representation of a combination reaction is: A + B à C 2. Decomposition reactions are those in which a compound breaks down into two or more simpler substances. The general representation of a decomposition reaction is AB à A + B. 3. Combustion reactions are those that produce a flame. The combustion reactions most commonly seen in this chapter involve a reactant containing C and H (and sometimes O) reacting with oxygen gas, O 2 , to form water and carbon dioxide. (See pages 87-88 of the text for examples.) III. Formula Weights Formula weights are calculated by adding the atomic weights of all of the atoms in a compound. e.g. The formula weight of Ca(NO 2 ) 3 is 164.1 amu (atomic mass units). Note that the smallest particles of covalent compounds are called molecules, whereas the smallest units of ionic compounds are called formula units. Therefore, formula weights are often called molecular weights when molecular compounds are involved. To get the
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Chem1201PReviewCh3 - Chemistry 1201 Review/Preview Chapter...

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