Solving First-Order Kinetics for [B] After 7.00 Minutes

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Discussion Overview

The discussion revolves around calculating the concentration of product [B] after a specified time in a first-order reaction A → B, given the rate constant and initial concentration of reactant [A]. Participants explore the application of the first-order kinetics formula and clarify the interpretation of results.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant applies the first-order kinetics formula and calculates the concentration of [A] remaining after 7 minutes, arriving at 0.066 M.
  • Another participant confirms the calculation of [A] but points out that the original question seeks the concentration of [B] produced, not [A] remaining.
  • A third participant expresses confusion about how to calculate the amount of [B] produced from the information given.
  • A later reply emphasizes that the decrease in [A] corresponds to the increase in [B], suggesting that the remaining amount of [A] indicates how much has been converted to [B].

Areas of Agreement / Disagreement

Participants generally agree on the calculation of [A] remaining but have not reached a consensus on how to derive the concentration of [B] produced from that information. The discussion remains unresolved regarding the exact calculation method for [B].

Contextual Notes

There are unresolved assumptions regarding the relationship between the concentrations of [A] and [B], and the participants have not explicitly defined the total initial concentration or the stoichiometry of the reaction.

Who May Find This Useful

This discussion may be useful for students or individuals studying chemical kinetics, particularly those working on first-order reactions and the interpretation of concentration changes over time.

geffman1
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We examine the reaction A B which displays first-order kinetics. We know that k = 0.30 / min.
If we begin with [A] = 0.54 M what will be after exactly 7.00 minutes?


hey i used the formula In[A]/[Ao]=-kt then rearranged to In[A]=-kt+[InAo]
when i sub it in i get In[A]=-0.3x7+In[0.54] and i get the answer 0.066 however the answer is 0.47M. i tired converting to second and still didnt work. any help would be good. thanks
 
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There's nothing wrong with your math.* The amount of [A] left is 0.066. The question is not asking you for the amount of [A] left. It is asking you for the amount of produced.

*Well, other than the fact that it is supposed to be Ln, not In. Natural Logarithm.
 
ta, how do i work out how much is produced?
 
dw, I am stupit. thanks mate
 
A is being converted to B in this chemical reaction, right? If 0.066 is left, what happened to the rest of it? It became B.
 

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