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General Chemistry

04/25/09

 

 


Reactants and Products

 

The reactants are the substances that are present before the chemical change takes place. They are the things that are present at the starting point. By convention, the chemical symbols for the reactants are written on the left hand side of the chemical reaction equation.

The products are the substances that are formed during the chemical change. They are the things that are present at the end. By convention, the chemical symbols for the products are written on the right hand side of the chemical reaction equation.

A reaction arrow is the symbol that signifies the actual change. A reaction arrow separates the reactants from the products. While a typical chemical reaction equation will include much more information, they all have the substances present before and after the chemical change with a reaction arrow to separate them. It has the basic form: HCl + NH3 NH4Cl. Some reaction equations have a double arrow separating the reactants and products. A double arrow signals that the reaction is in equilibrium, a situation in which the reactants are changing into products at the same time as the products are changing back into reactants.

The chemical information in the reaction equation can be thought of as number and kinds of atoms needed and formed. Note that the number and kinds of atoms on both sides of the reaction arrow are the same. In this case, one nitrogen atom, one chlorine atom, and four hydrogen atoms take part in this particular chemical change. Because a mole is a collection of atoms or molecules, it is more convenient to consider reaction equations as information about the number and kinds of moles of substances taking part in the chemical change. In the above example, one mole of hydrogen chloride (or hydrochloric acid) and one mole of ammonia react to form one mole of ammonium chloride. Remember to consider all of the information associated with the chemical formulas. We know that hydrogen chloride (or hydrochloric acid) is an acid, ammonia is a molecular compound, and ammonium chloride is an ionic compound.


Concept Check:  What are the reactants in this reaction equation:  HNO3 + NaHCO3 --> NaNO3 + CO2 + H2O?

Answer: The nitric acid, HNO3, and the sodium hydrogen carbonate, NaHCO3, are the reactants.


 

 

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