Question

How are the reactions classified on the basis of rates of reactions? Give examples.

Short answer

Question: What are the three classifications of reactions based on their rates, and provide an example for each classification. Answer: The three classifications of reactions based on their rates are: 1. Fast reactions: These occur rapidly, often within fractions of a second, and usually release large amounts of energy. For example, the combustion of hydrogen in air: \[2H_2(g) + O_2(g) \rightarrow 2H_2O(g)\] 2. Moderate reactions: These reactions take place at a noticeable but not extremely rapid pace, lasting from a few seconds to several minutes. For example, the precipitation of silver chloride from its soluble components: \[AgNO_3(aq) + NaCl(aq) \rightarrow AgCl(s) + NaNO_3(aq)\] 3. Slow reactions: These reactions take a considerable amount of time to occur, from a few hours to days, months, or even years. For example, the formation of rust on iron in the presence of water and oxygen: \[4Fe(s) + 3O_2(g) + 6H_2O(l) \rightarrow 4Fe(OH)_3(s)\]

Step-by-step solution

Understanding Reaction Rates

Reaction rates refer to the speed at which reactants are transformed into products in a chemical reaction. The rate of a reaction is influenced by various factors, such as temperature, pressure, concentration of reactants, and presence of catalysts. Reactions can be classified into three categories based on their rates: fast reactions, moderate reactions, and slow reactions.

Fast Reactions

Fast reactions are chemical reactions that occur rapidly, often within fractions of a second. Many fast reactions release large amounts of energy, such as heat, light, or sound. The high energy release is usually a consequence of highly reactive substances being involved in the reaction. Example: Combustion of hydrogen in air: \[2H_2(g) + O_2(g) \rightarrow 2H_2O(g)\] This reaction is a fast reaction that generates heat and water vapor. Fast reactions are often used in applications where rapid energy release is desirable, such as in explosives or rocket propulsion.

Moderate Reactions

Moderate reactions are chemical reactions that take place at a noticeable but not extremely rapid pace. These reactions might last from a few seconds to several minutes. Examples of moderate reactions can be found in everyday life processes, such as the breakdown of glucose to produce energy in the human body or the ripening of fruit. Example: Precipitation of silver chloride from its soluble components: \[AgNO_3(aq) + NaCl(aq) \rightarrow AgCl(s) + NaNO_3(aq)\]

Slow Reactions

Slow reactions are chemical reactions that take a considerable amount of time to occur, lasting from a few hours to days, months, or even years. Slow reactions are usually accompanied by a gradual change in the properties of the reacting substances. Examples of slow reactions include corrosion and biological growth. Example: Formation of rust on iron in the presence of water and oxygen: \[4Fe(s) + 3O_2(g) + 6H_2O(l) \rightarrow 4Fe(OH)_3(s)\] In summary, reactions can be classified into fast, moderate, and slow reactions based on their rates of reactions. Fast reactions happen quickly and often release large amounts of energy, moderate reactions are noticeable but not overly rapid, and slow reactions take a long time to occur with gradual changes in the reacting substances' properties.