How Does Changing Concentration Affect the Rate of a Chemical Reaction?

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Discussion Overview

The discussion revolves around the effect of changing concentrations on the rate of a chemical reaction, specifically focusing on the reaction 2NO(g) + O2(g) ---> 2NO2(g). Participants explore the implications of reaction orders and seek assistance with specific homework problems related to calculating reaction rates under varying concentrations.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant states the rate equation as v=k[O2][NO]², indicating the relationship between concentration and reaction rate.
  • Another participant explains that the "orders" refer to the powers to which the concentrations are raised, which are derived from stoichiometric ratios of the reactants.
  • A different viewpoint suggests that reaction orders do not always correlate directly with stoichiometric coefficients, citing the example of the halogenation of acetone, where the rate is dependent on the concentration of acid but independent of halogen concentration.
  • The original poster expresses confusion regarding the meaning of "second order in NO" and seeks guidance on how to approach the homework problems.

Areas of Agreement / Disagreement

Participants present differing views on the relationship between reaction orders and stoichiometric coefficients, indicating a lack of consensus on this aspect. The original poster's confusion about the homework problems remains unresolved.

Contextual Notes

The discussion includes unresolved mathematical steps related to the calculations of reaction rates and the interpretation of reaction orders. The original poster's understanding of the concepts appears incomplete, which may affect their ability to solve the problems presented.

Who May Find This Useful

Students studying chemical kinetics, particularly those working on homework related to reaction rates and orders of reactions.

tensirk
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Homework Statement


The reaction 2NO(g) + O2(g) ---> 2NO2(g) is second order in NO and first order in O2.
When [NO] = 1 M and [O2] = 1.9 M, the observed rate of disappearance of NO is 0.00017670 M/s.

I have already found the value of the rate constant to be 2. I found that the units of the rate constant are M-2s-1. I lastly found that the rate of the reaction would increase if the concentration of NO were increased by a factor of 1.4.

Now I am having a lot of trouble figuring out these last two problems:
1. By what factor would the rate of reaction of NO increase? [if it were increased by a factor of 1.4]
2. What is the rate of reaction when [NO] = 0.1 M and [O2] = 0.19 M?

Homework Equations


Honestly, I don't even know where to begin in terms of equations for these two problems.

The Attempt at a Solution


I think where I'm having trouble is understanding what "second order in NO" means. Any guidance on these problems would be MUCH appreciated, as I feel completely lost. Thanks in advance!
 
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v=k[O2][NO]2
 
The "orders" are the powers to which the concentrations are raised. These come from the stoichiometric ratios of the reactants.
 
cep said:
The "orders" are the powers to which the concentrations are raised. These come from the stoichiometric ratios of the reactants.

Not necessarily. For instance, the rate of halogenation of acetone is proportional to the concentration of acid, and is independent of the concentration of halogen.
 

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