WEIGHT RELATIONS IN CHEMICAL. REACTIONS

In every branch of chemistry it is necessary to make calculations about the weights of substances involved in chemical reactions and sometimes calculations of this sort are of interest in every-day life. These calculations are called stoichiometric calculations (from the Greek stoicheion, elementary constituent, and metrein, to measure). 

Analyze each stoichiometric problem that you meet do not memo-. rize rules for solving these problems. When you have such a problem to solve, think about it until you are sure that you understand it in particular, consider the behavior of the atoms involved. Then formulate an equation containing the upknown quantities, making use of atomic weights, and solve it. It is often helpful to solve a problem in steps, as is done in Example 6 below. 

A symbol such as Cu is used to indicate the element topper, either in the elementary substance or in compounds. It also ipeans a definite amount of copper—one atom or onfc atomic weight (63.57) in any 

Often the state of aggregation of a substance is represented by appended letters Cu(s) refers to crystalline copper (s standing for solid), Cu(/) to liquid copper, and Cu(g) to gaseous copper. Sometimes a substance is indicated as solid or crystalline by a line drawn under its formula (both AgCl and AgCl (s) mean solid silver chloride). A sub stame in solution is sometimes represented by its formula followed by aq (for aqiiec us solution). 

The way to work a stoichiometric problem is by thinking about the problem in terms of atoms and molecules, and then deciding how to 

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All of the weight relations in chemical reactions depend upon the weights of the atoms of the elements. These weights (or masses), called atomic weights, are ery important in the stud> and practice of chemistry. 

Co to http //now.brookscole.com/ cracoliceSe and click Chemistry Interactive for the module Weight Relations in Chemical Reactions. 

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