Examples of reaction rate in the following topics:
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- The rate law for a chemical reaction relates the reaction rate with the concentrations or partial pressures of the reactants.
- The rate law for a chemical reaction is an equation that relates the reaction rate with the concentrations or partial pressures of the reactants.
- Lastly, k is known as the rate constant of the reaction.
- A smaller rate constant indicates a slower reaction, while a larger rate constant indicates a faster reaction.
- The rate law equation for this reaction is: $Rate = k[NO]^{1}[O_{3}]^{1}$.
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- Rate laws for reactions are affected by the position of the rate-determining step in the overall reaction mechanism.
- Since the first step is the rate-determining step, the overall reaction rate for this reaction is given by this step: $\text{rate}=k[H_2][ICl]$.
- At equilibrium, the rate of the forward reaction will equal the rate of the reverse reaction.
- Therefore, the rate law must contain no reaction intermediates.
- Combine elementary reaction rate constants to obtain equilibrium coefficients and construct overall reaction rate laws for reactions with both slow and fast initial steps
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- Obviously, there are factors that affect the rates of chemical reactions.
- Each reaction also has a reaction rate.
- Reaction rates are not usually constant over a given reaction time.
- Instead, the reaction rate can be accurately modeled by a rate equation.
- You can read more about reaction rates and rate laws in the Kinetics unit.
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- Raising the concentrations of reactants makes the reaction happen at a faster rate.
- By doubling the concentration, the rate of reaction has doubled as well.
- Increasing the pressure for a reaction involving gases will increase the rate of reaction.
- Similarly, the rate of reaction will decrease with a decrease in temperature.
- Explore the role of temperature on reaction rate.
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- How the rate of a reaction is measured will depend on what the reaction is and what product forms.
- The following examples describe various ways to measure the rate of a reaction.
- The rate of a reaction that produces a gas can also be measured by calculating the mass loss as the gas forms and escapes from the reaction flask.
- In a reaction in which a precipitate is formed, the amount of precipitate formed in a period of time can be used as a measure of the reaction rate.
- Produce rate expressions when given chemical reactions and discuss methods for measuring those rates
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- A zero-order reaction has a constant rate that is independent of the concentration of the reactant(s); the rate law is simply $rate=k$ .
- Unlike the other orders of reaction, a zero-order reaction has a rate that is independent of the concentration of the reactant(s).
- The rate law for a zero-order reaction is rate = k, where k is the rate constant.
- In the case of a zero-order reaction, the rate constant k will have units of concentration/time, such as M/s.
- This is the integrated rate law for a zero-order reaction.
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- The rate-determining step is the slowest step in a reaction mechanism.
- Because it is the slowest, it determines the rate of the overall reaction.
- However, we cannot simply add the rate laws of each elementary step in order to get the overall reaction rate.
- Determining the overall reaction rate from the reaction mechanism will be discussed in the next concept.
- Write rate laws for elementary reactions, explaining how the order of the reaction relates to the reaction rate
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- The rate of a multi-step reaction is determined by the slowest elementary step, which is known as the rate-determining step.
- In kinetics, the rate of a reaction with several steps is determined by the slowest step, which is known as the rate-determining, or rate-limiting, step.
- If this reaction occurred in a single step, its rate law would be:
- The fact that the experimentally-determined rate law does not match the rate law derived from the overall reaction equation suggests that the reaction occurs over multiple steps.
- Describe the relationship between the rate determining step and the rate law for chemical reactions
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- If the reaction were second-order in either reactant, it would lead to the following rate laws:
- The second scenario, in which the reaction is first-order in both A and B, would yield the following rate law:
- If we are interested in determining the order of the reaction with respect to A and B, we apply the method of initial rates.
- Therefore, the overall order for the reaction is second-order $(2+0=2)$, and the rate law will be:
- A table showing data for three trials measuring the various rates of reaction as the initial concentrations of A and B are changed.
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- A first-order reaction depends on the concentration of one reactant, and the rate law is: $r=-\frac{dA}{dt}=k[A]$ .
- Using the Method of Initial Rates to Determine Reaction Order Experimentally
- Since there is only one reactant, the rate law for this reaction has the general form:
- By comparing these rates, it is possible for us to find the order of the decomposition reaction.
- Design initial rate experiments to determine order of reaction with respect to individual reactants