Irreversible chemical reaction

In summary, reversible processes occur at equilibrium where the driving force is only slightly greater than the opposing force, while irreversible processes are not at equilibrium and are spontaneous. The reaction in irreversible processes only occurs in one direction, but to some extent, it still occurs in the opposite direction at a slower rate. This is different from the terms reversible and irreversible in the context of thermo-mechanical processes.
  • #1
tonyjk
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3
Hello,
"Reversible processes are at equilibrium : Driving force is only infinitesimally greater than the opposing force Process occurs in a series of infinitesimal steps, and at each step the system in at equilibrium with the surroundings It would take an infinite amount of time to carry out. However Irreversible Process are not at equilibrium; thus a spontaneous process"

http://www.columbia.edu/itc/chemistry/environmental/lectures/Ch_13.pdf page 4.

During irreversible chemical reaction, the reaction is happening in one direction. My question is does the reaction is also happening in the second direction but at lower rate? Or it depends (Some of chemical reaction can occur in both directions but at different rate however others can only occur in one direction like combustion)?

Thanks.
 
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  • #2
You are aware that the terms reversible and irreversible in the context of the thermo-mechanical part of thermo are different from the terms reversible and irreversible in the context of chemical reactions in thermo, right? (An unfortunate circumstance)

Chet
 
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Likes tonyjk
  • #3
Chestermiller said:
You are aware that the terms reversible and irreversible in the context of the thermo-mechanical part of thermo are different from the terms reversible and irreversible in the context of chemical reactions in thermo, right? (An unfortunate circumstance)

Chet
Yes
 
  • #4
tonyjk said:
Yes
All reactions are reversible to some extent. It's just that for reactions that we call irreversible, the thermodynamics strongly favors the products over the reactants. In terms of kinetics, this means that the reverse reaction rate is much slower than the forward reaction rate. Equivalently, in terms of thermo, the equilibrium constant is very large.

Chet
 

1. What is an irreversible chemical reaction?

An irreversible chemical reaction is a process in which reactants are converted into products and cannot be reversed back to their original state. This means that the products formed are stable and cannot be easily broken down into their reactants again.

2. What causes a chemical reaction to be irreversible?

There are several factors that can contribute to an irreversible chemical reaction. One of the main reasons is the presence of a catalyst or an enzyme that speeds up the reaction and makes it difficult to reverse. Additionally, irreversible reactions often involve the formation of new bonds that are stronger than the original ones, making it energetically unfavorable for the reaction to reverse.

3. How can we identify if a chemical reaction is irreversible?

There are a few ways to determine if a chemical reaction is irreversible. One way is to observe the reaction over time and see if it reaches an equilibrium state or if it continues to proceed in one direction. Another method is to measure the change in enthalpy, or heat, during the reaction. If the enthalpy change is negative, the reaction is likely irreversible.

4. Are all irreversible reactions exothermic?

No, not all irreversible reactions are exothermic. While many irreversible reactions do release energy in the form of heat, there are also irreversible reactions that absorb energy from their surroundings, known as endothermic reactions. The change in enthalpy is what determines whether a reaction is exothermic or endothermic.

5. Can an irreversible reaction ever be reversed?

In theory, an irreversible reaction can be reversed if the conditions are right. However, in practical terms, it is very difficult to reverse an irreversible reaction. The energy required to break the strong bonds formed during the reaction is often too high to be feasible. Additionally, the presence of a catalyst or enzyme that facilitated the reaction may no longer be present, making it even more challenging to reverse the reaction.

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