What would happen to the reaction rate of a solution if 10 mL or more of water is added? Will the reaction rate increase or decrease?
The following reaction occurs without a change in the color
2A (g) + B2(g) --- 2AB (g)
a) How could you monitor the concentration of the reactants?
b) How would you determine the reaction orders?
c) How would you find the rate constant and the units for the rate constant?
Doesn't adding water dilute the solution? How would lowering the concn of the reactants affect the rate?
2a) Since all of the molecules are gases, I see three moles on the left and two moles on the right. So would that affect the pressure? Could you monitor the pressure change?
b)& c). I assume you have had this in class. Change concn of A while holding B constant and measure rate. Do same for B and A (but reversed). That will give orders. Then plug in rates, concns, and orders to determine k.
To determine what would happen to the reaction rate if 10 mL or more of water is added, we need to consider the stoichiometry of the reaction.
1. Reaction Rate with Water Added:
If 10 mL or more of water is added to the reaction mixture, it would effectively dilute the concentration of the reactants. In the given reaction, water is not involved as a reactant, so adding water would increase the total volume of the solution, while the concentrations of A and B would decrease. As a result, the reaction rate would decrease.
Now, let's address the related questions:
a) Monitoring Concentration of Reactants:
To monitor the concentration of the reactants, you can use various techniques, such as spectroscopy or titration. In this specific case, since the reaction does not result in a change in color, applying spectroscopy would not be appropriate. A suitable method might be to perform a titration using a known reagent that reacts stoichiometrically with one of the reactants (A or B). By carefully measuring the volume of the reagent needed to reach the endpoint, you can determine the initial concentration of the reactant.
b) Determining Reaction Orders:
To determine the reaction orders, the method of initial rates can be used. This involves carrying out multiple experiments with different initial concentrations of reactants while keeping all other factors constant. By comparing the initial rates of reaction at different concentrations, you can determine the reaction orders for A and B. The order of a reactant can be determined by observing how changes in the concentration of that reactant affect the rate of the reaction.
c) Finding the Rate Constant and Units:
The rate constant, k, can be determined using the rate equation for the reaction. The rate equation gives the mathematical relationship between the concentrations of the reactants and the reaction rate. Once the rate equation is established, the rate constant can be calculated by substituting the known values of concentrations and rate into the equation. The units for the rate constant will depend on the overall order of the reaction, which can be determined experimentally using the method described in step b. The units of the rate constant can be obtained by performing the necessary dimensional analysis.