What Is a Chemical Reaction?
A chemical reaction is a process by which one or more substances, or reactants, are changed into one or more different substances, or products This process usually involves the formation and breaking of chemical bonds between atoms or molecules, and it often involves the release of energy.
Chemical reactions can include a variety of processes. A common type of reaction is a combination reaction, which involves two or more molecules combining to form a single product. Another type of reaction is a decomposition reaction, which involves a single reactant breaking down into two or more products. A displacement reaction occurs when an element reacts with a compound to replace one of the elements within the compound. Oxidation-reduction reactions, or redox reactions, involve a loss or gain of electrons.
Finally, a catalytic reaction is one in which a catalyst is used to speed up the reaction without itself being affected by the reaction. In such reactions, the reactants remain unchanged and a new product is formed.
The pH Scale
The pH scale is a tool used to measure the acidity or alkalinity of a solution. It is measured on a logarithmic scale from 0-14 with 7 being neutral. Solutions with a pH less than 7 are considered acidic, while solutions with a pH greater than 7 are considered basic, or alkaline.
The pH scale is an important factor when attempting to predict the outcome of a chemical reaction. Acids and bases can react to form salts, and the pH of the reaction will often determine the type of salt formed. Acids have a low pH and can react with bases to form a salt, while bases have a high pH and can react with acids to form a salt.
Examples of Chemical Reactions and the pH Scale
1. Combination of Hydrochloric Acid and Sodium Hydroxide: This reaction involves the combination of hydrochloric acid (HCl) with sodium hydroxide (NaOH). The resulting product is a salt called sodium chloride (NaCl) and water. The pH of this reaction is 7, which is neutral.
2. Oxidation of Iron: This reaction occurs when iron (Fe) is exposed to oxygen (O2). The resulting product is iron oxide (Fe2O3) and water. The pH of this reaction is slightly acidic.
3. Combination of Acetic Acid and Sodium Bicarbonate: This reaction involves the combination of acetic acid (CH3COOH) with sodium bicarbonate (NaHCO3). The resulting product is a salt called sodium acetate (CH3COONa) and water. The pH of this reaction is slightly basic.
4. Decomposition of Ammonium Nitrate: This reaction involves the decomposition of ammonium nitrate (NH4NO3). The resulting products are nitrogen (N2) and water. The pH of this reaction is slightly acidic.
5. Combination of Magnesium and Hydrochloric Acid: This reaction involves the combination of magnesium (Mg) with hydrochloric acid (HCl). The resulting product is a salt called magnesium chloride (MgCl2) and hydrogen (H2). The pH of this reaction is neutral.