Chemical equations symbols commonly used

Table 8-1 Symbols Commonly Used in Chemical Equations...

Figure 1.5 above summarizes the symbols commonly used in chemical equations. As you can see, some things can be shown in different ways. For example, sometimes a gaseous product is indicated by an arrow pointing upward, , instead of (g). A downward arrow, J., is often used to show the formation of a precipitate during a reaction in solution. 

Symbols are ttsed exterrsively in teaching and leartring chemistry atrd these symbolie representatiorrs take a wide variety of forms. The very common represerrtation of chemical reactiorrs through equations will be used as the basis for mueh of the... 

Given this context, the use of chemical symbols, formulae and equations can be readily misinterpreted in the classroom, because often the same representations can stand for both the macroscopic and sub-microscopic levels. So H could stand for an atom, or the element hydrogen in an abstract sense H2 could mean a molecule or the substance. One common convention is that a chemical equation represents molar quantities, so in Example 9 in Table 4.1,... 

Kinetic equations are commonly expressed in terms of the amount-of-substance concentrations of the chemical species involved. The amount-of-substance concentration is the amount of substance (for which the SI unit is the mole, symbol mol) divided by the volume. As it is the only kind of concentration commonly used in biochemistry it is usually abbreviated to concentration and this shorter form will be used in the remainder of this document without further discussion. The unit almost invariably used for concentration is mol dm", which is alternatively written as mol L, mol 1, or simply KMK (molar). "- ... 

When you write chemical equations, it is absolutely essential that you write the formulas of these seven diatomic elements as two-atom molecules with a subscript 2 following the symbol of the element. Failure to do so is probably the most common mistake made by beginning chemistry students. The formulas of other elements are the same as their elemental symbols. No subscript is used. 

The (g) indicates that these substances are gases in the reaction. Table 3.6 summarizes the common states of reactants and products and their symbols used in chemical equations. 

The concentration scale of a standard chemical potential and an activity coefficient are specified by additional symbols placed as either the subscript or superscript. For example, the mole fraction scale is specified in Equation 1.3. In this equation, if we want to be precise, should be called the standard chemical potential on the mole fraction concentration scale. Equation 1.3 is usually used for solutions of nonelectrolytes, such as 02(aq), and for solvent (water) in electrolyte solutions. Also, this equation can be used for solid solutions such as metal alloys. For electrolyte solutions, molality is commonly used except (1) electrolyte conductivity and (2) electrochemical kinetics, where molarity is commonly used. 

Throughout the remainder of this book, the Greek letter delta (A) will be used to symbolize change. Chemists use the term enthalpy for the heat content of a substance or the heat of a reaction, so the H in the previous equation means enthalpy. The equation states that the change in enthalpy during a reaction equals the enthalpy of the products minus the enthalpy of the reactants. You can consider enthalpy to be chemical energy that is commonly manifested as heat. 

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