Are all substitution reactions reversible?

In summary, the conversation discusses a reaction between H2 and CuCl2, which is a substitution reaction. However, it is unlikely to be reversible due to the lower reactivity of Cu compared to H. The discussion also mentions the relation between Gibbs energy and the rates of direct and reverse reactions, and the difficulty of reversing the reaction due to the large difference in Gibbs energy between HCl and CuCl2. This is supported by the high value of Keq at room temperature.
  • #1
Akash47
53
5
Consider a reaction:
H2+CuCl2= Cu+2HCl
This is a substitution reaction.But is this may not be a reversible reaction since Cu is less active than .So Cu can't substitute H from HCl and make a backward reaction.Is my thinking right?
 
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  • #2
Akash47 said:
Consider a reaction:
H2+CuCl2= Cu+2HCl
This is a substitution reaction.But is this may not be a reversible reaction since Cu is less active than .So Cu can't substitute H from HCl and make a backward reaction.Is my thinking right?
See Gibbs energy relation to the rate of direct and reverse reaction.
You need to sum entropic and enthalpic parts of Gibbs energy on left and right part of reaction equation to find the rates of both reverse and direct reaction.
 
  • #3
trurle said:
See Gibbs energy relation to the rate of direct and reverse reaction.
You need to sum entropic and enthalpic parts of Gibbs energy on left and right part of reaction equation to find the rates of both reverse and direct reaction.
But isn't my opinion right what I've said in my first post?
 
  • #4
Akash47 said:
Consider a reaction:
H2+CuCl2= Cu+2HCl
This is a substitution reaction.But is this may not be a reversible reaction since Cu is less active than .So Cu can't substitute H from HCl and make a backward reaction.Is my thinking right?
At room temperature, Gibbs energy:
Of HCl: -2*131170+2*51(T-T0)
Of CuCl2: -1*103000+2*91(T-T0)
You can see the HCl Gibbs energy of HCl is much more negative, and difference of entropies is small so heating do not help much.
According to
9f654171eeefde32716ba2c59ac50696c77a977b

equation,
Keq=5*10^27 for reaction in question at room temperature, this mean reaction is very difficult to reverse to the formation of copper chloride.
 

1. What is a substitution reaction?

A substitution reaction is a type of chemical reaction where one atom or group of atoms in a molecule is replaced by another atom or group of atoms. This can result in a new molecule with different properties.

2. Are all substitution reactions reversible?

No, not all substitution reactions are reversible. Some substitution reactions are irreversible, meaning that once the reaction has occurred, it cannot be reversed to reform the original reactants.

3. How do you know if a substitution reaction is reversible?

The reversibility of a substitution reaction depends on the specific reactants and conditions involved. Generally, if the products of a substitution reaction are stable and the reaction occurs under mild conditions, it is more likely to be reversible.

4. Can a reversible substitution reaction reach equilibrium?

Yes, a reversible substitution reaction can reach equilibrium if the forward and reverse reactions occur at equal rates. This means that the concentration of products and reactants will remain constant over time.

5. What factors can affect the reversibility of a substitution reaction?

Some factors that can affect the reversibility of a substitution reaction include the stability of the products, the strength of the bonds involved, and the conditions under which the reaction occurs (such as temperature and pressure).

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