- #1
RPN
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Hello,
I really want to thank everyone that has helped me in understanding chemistry. I have started a few questions on rates of reactions and would love it if someone could look over my answers and see if I am headed in the right direction.
1)
The rate of a simple chemical reaction like,
NO(g) + ½ O2(g) ---- NO2(g), are most rapid at the beginning of the reaction due to several reasons. First the reaction occurs in a single step and is called a bimolecular reaction. Secondly rate of reactions are affected by the reactants concentrations. In the beginning of a reaction the concentrations of the reactants are at their highest and more collisions between reactant molecules occur. As we know concentrations change most rapidly at the beginning of a reaction. This equation consists of simple ions that combine in a one-to-one ratio. With all these factors combined it can be predicted that this reaction would be rapid in the beginning.
2)
In three ways I will dissolve a lump of sugar in water by increasing the rate at which it will dissolve.
Method one: To increase the rate of dissolution of sugar I will increase the temperature of the water. By increasing the temperature of the water I will in turn be increasing the kinetic energy and the threshold energy (activation energy). When the activation energy is decreased the reaction rate increases. When the kinetic energy is increased this translates to an increased frequency of collisions as the particles are moving more rapidly. This increases their chances for collisions thus increasing the chance of successful collisions. It is said that a temperature increase of 10oC can either double or triple the rate of reaction.
Method two: I could crush the lump of sugar into granules and thus increasing the surface area. Increasing the surface area of the solid phase in a heterogeneous reaction increases the rate of reaction. Comparing the rate of reaction of the lump of sugar in water to the granules of sugar in water, the lump dissolves more slowly than the granules.
Method three: I could use a catalyst in order to speed of the rate of reaction. A catalyst is any reagent that increases the rate of reaction but is not consumed during the reaction. By adding a chemical substance we give a reaction a new route to take in order to get the products. Catalysts increase reaction rates by providing a lower activation energy pathway for the reactants. The catalysts are assumed to form an intermediate activated complex that has a lower activation energy.
3)
a) The effect of a temperature increase on the rate constant of the forward reaction would be an increase in the reaction. An increase in temperature would increase the energy of the system closer to the activation energy and speed the reaction up.
b) The effect of a temperature increase on the rate constant of the reverse reaction would also be an increase in the rate of reaction. Increasing the temperature increases the rate of the reverse reaction to a greater extent than it does the rate of the forward reaction.
Thank you so much
I really want to thank everyone that has helped me in understanding chemistry. I have started a few questions on rates of reactions and would love it if someone could look over my answers and see if I am headed in the right direction.
1)
The rate of a simple chemical reaction like,
NO(g) + ½ O2(g) ---- NO2(g), are most rapid at the beginning of the reaction due to several reasons. First the reaction occurs in a single step and is called a bimolecular reaction. Secondly rate of reactions are affected by the reactants concentrations. In the beginning of a reaction the concentrations of the reactants are at their highest and more collisions between reactant molecules occur. As we know concentrations change most rapidly at the beginning of a reaction. This equation consists of simple ions that combine in a one-to-one ratio. With all these factors combined it can be predicted that this reaction would be rapid in the beginning.
2)
In three ways I will dissolve a lump of sugar in water by increasing the rate at which it will dissolve.
Method one: To increase the rate of dissolution of sugar I will increase the temperature of the water. By increasing the temperature of the water I will in turn be increasing the kinetic energy and the threshold energy (activation energy). When the activation energy is decreased the reaction rate increases. When the kinetic energy is increased this translates to an increased frequency of collisions as the particles are moving more rapidly. This increases their chances for collisions thus increasing the chance of successful collisions. It is said that a temperature increase of 10oC can either double or triple the rate of reaction.
Method two: I could crush the lump of sugar into granules and thus increasing the surface area. Increasing the surface area of the solid phase in a heterogeneous reaction increases the rate of reaction. Comparing the rate of reaction of the lump of sugar in water to the granules of sugar in water, the lump dissolves more slowly than the granules.
Method three: I could use a catalyst in order to speed of the rate of reaction. A catalyst is any reagent that increases the rate of reaction but is not consumed during the reaction. By adding a chemical substance we give a reaction a new route to take in order to get the products. Catalysts increase reaction rates by providing a lower activation energy pathway for the reactants. The catalysts are assumed to form an intermediate activated complex that has a lower activation energy.
3)
a) The effect of a temperature increase on the rate constant of the forward reaction would be an increase in the reaction. An increase in temperature would increase the energy of the system closer to the activation energy and speed the reaction up.
b) The effect of a temperature increase on the rate constant of the reverse reaction would also be an increase in the rate of reaction. Increasing the temperature increases the rate of the reverse reaction to a greater extent than it does the rate of the forward reaction.
Thank you so much