Consider the following two reactions:
5 Fe2+(aq)+MnO41-(aq)+8 H1+(aq)-->5Fe3(aq)+Mn2+(aq)+4 H2O(l)
2 MnO41-(aq)+5 C2O42-(aq)+16 H1+(aq)-> 2 Mn2+(aq)+CO2 g)+8 H2O(l)
Both of these reactions result in the purple permanganate (MnO41-(aq)) ion reacting to form the colourless manganese (II) ion. The difference is that the first reaction happens in a few seconds, while the second occurs over several minutes. Explain why this so, based on what you know of chemical reactions and what you can see in these two reaction equations.
Based on the reaction equations given, we can analyze the factors that contribute to the difference in reaction rates.
1. Concentration: In the first reaction, there are only three reactants (Fe2+, MnO4-, and H+), whereas the second reaction involves five reactants (MnO4-, C2O4^2-, H+, CO2, and H2O). The greater number of reactants in the second reaction leads to a higher probability of collisions between particles. This increased collision frequency favors a higher reaction rate in the first reaction.
2. Reactant Properties: The second reaction includes oxalate ions (C2O42-) as a reactant. Oxalate ions are known to form complexes with manganese ions, which can slow down the reaction rate. Formation of complexes makes it more difficult for the reactants to come into contact and react effectively, resulting in a slower reaction rate compared to the first reaction.
3. Activation Energy: The activation energy is the energy required for a chemical reaction to occur. Even though both reactions involve the same reactants, the activation energy for each reaction may differ. The first reaction may have a lower activation energy, allowing for a faster reaction rate.
4. Catalysts: The presence of catalysts can greatly affect the reaction rate. Catalysts provide an alternative reaction pathway with a lower activation energy, allowing the reaction to occur more rapidly. It is possible that the first reaction is catalyzed by a substance present in the reaction mixture, while the second reaction lacks a catalyst.
Overall, the differences in concentration, reactant properties, activation energy, and potential presence of a catalyst contribute to the contrasting reaction rates observed in the two reactions.