$$\ce{Li2O + 2KCl <=> 2LiCl + K2O}$$

I got this reaction on a test question paper. With three other options, it was asked whether this reaction is feasible or not?

I googled it and found the reverse reaction of at every webpage I looked. So, it seems to me it isn't feasible.

I think that the reverse reaction is feasible because $\ce{LiCl}$ is quite covalent in nature(Fajan's rule) So, for becoming more ionic in nature $\ce{Li+}$ makes bond with oxygen ion. (I now think it's a bogus reasoning)

What could be the reason behind it? Is it feasible?


1 Answer 1


Although every reaction is reversible in nature, let's try to understand where the equilibrium might be biased, i.e. whether the reactant side favoured or the product side.

A rule of thumb while predicting feasibility is to remember, a reaction where you can get a weak acid from a strong acid is feasible.

$$\ce{Strong Acid -> Weak acid}$$

In your case we're dealing with $\ce{KCl}$ and $\ce{LiCl}$. The acidic or basic nature or salts is determined by the extent of hydrolysis of its ions. Ions from a weaker species undergo hydrolysis while ions from a stronger species don't. Another way to look at this is to compare the acidic and basic strengths of the acids and bases which formed them in the first place. $$\ce{LiOH + HCl -> LiCl + H2O}$$ $$\ce{KOH + HCl -> KCl + H2O}$$ Notice that $\ce{HCl}$ is common to both of these species, so we have to just compare the basic strengths of $\ce{LiOH}$ and $\ce{KOH}$. Down the group (in alkali metal hydroxides) basic strength increases. So $\ce{KOH}$ is a better base. And thus $\ce{KCl}$ is a weaker acid. Since we're making a stronger acid from a weaker acid, the reaction can be termed as unfeasible.


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