Chemical equations information conveyed

Some additional information that can be conveyed in a balanced chemical equation (s) = solid, (g) = gas, (aq) = aqueous, and (1) = liquid. The following equation shows the proper use of these symbols S(s) + 6HN03(aq) —> H2S04(aq) + 6N02(g) + 2H20(1). It should be noted that [aq] means aqueous solution and [1] means in the liquid phase of a pure substance. Use phase-indicating symbols in your balanced equation in no. 3 above. 

This type of equation is often called a skeleton equation. It indicates which reactants were involved and what products were formed, but little else. The addition of a few more symbols can provide much more information. What s missing in the chemical equation that was present in the word equation is the states of the chemicals. The word equation specified sodium metal and hydrogen gas, yet the chemical equation does not indicate this. By rewriting the equation, we can convey this information ... 

You may have noticed that chemical equations are sometimes written with more information than at other times. For example, I don t always include the subscripts (for example, (s) or (g)), which indicate the state of the matter at the time of the reaction. Also, I don t always indicate whether energy is present as a reactant or as a product. When you use these notations depends upon the type of information that you want to convey at a given time. In general, it is always okay to show more information than you need to. In the next lesson you will learn how to show energy changes in chemical equations. 

Interpret information conveyed by a balanced chemical equation (Section 4.1). 

Word equations convey useful information, but the chemical equations used by chemists convey much more ... 

We use chemical equations to help us describe chemical reactions. For a reaction involving ions, we have a choice of chemical equations, depending on the kind of information we want to convey. We can represent such a reaction by a molecular equation, a complete ionic equation, or a net ionic equation. 

In the reaction in Example 4-1, triethylene glycol is a liquid, oxygen and carbon dioxide are gases, and water is a liquid. Such facts as these are inconsequential if our interest is only in balancing an equation. Still, we convey a more complete representation of the reaction by including this information, and sometimes it is essential to include such information in a chemical equation. The state of matter or physical form of reactants and products is shown by symbols in parentheses. 

Once the values of a, jS, etc. are determined, the rate law is defined. Reaction order is an experimental quantity and conveys only information about the manner in which rate depends on concentration. One should not use order to mean the same as molecularity, which concerns the number of reactant particles (atoms, molecules, free radicals, or ions) entering into an elementary reaction. An elementary reaction is one in which no reaction intermediates have been detected, or need to be postulated to describe the chemical reaction on a molecular scale. Until other evidence is found, an elementary reaction is assumed to occur in a single step and to pass through a single transition state (Bunnett, 1986). The stoichiometric coefficients in the denominators of the differentials of Eq. (2.2) guarantee that the equation represents the rate of reaction regardless of whether rate of consumption of a reactant or of formation of a product is considered. 

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