This is how my chemistry professor compared reaction of a weak and a strong acid with water:
$$\ce{HCl + H2O -> H3O+ + Cl- + Heat}$$ In this case $\ce{H2O}$ breaks the bond between $\ce{H}$ and $\ce{Cl}$ in $\ce{HCl}$ which results in he formation of $\ce{H+}$ and $\ce{Cl-}$ ions. The $\ce{H+}$ ion combines with $\ce{H2O}$ to form $\ce{H3O+}$ (also known as hydronium). Since adding water to an acid causes its hydration, which is an exothermic process, the reaction also results in the emission of heat. This reaction favors going to the right hand side of the equation. $$\ce{CH3COOH + H2O <=> H3O+ + CH3COO- + Heat}$$ In this case, the size of the acid is greater than the size of $\ce{HCl}$. It means that the process of hydration will be slower. This will lead to a comparatively less number of $\ce{H+}$ ions being combined with water. So, considering Arrhenius' definition of acids, $\ce{CH3COOH}$ is a weaker acid than $\ce{HCl}$. Also, this reaction is going to be reversible.
Now, my questions are as follows:
- Why the first reaction favors going to the right hand side of the equation? I think that it has something to do with heat as the heat is lost to the surroundings and the energy level on right hand side decreases. I am still not sure.
- Why is the second reaction reversible? I have no idea of why it is reversible so I can't provide my opinions.
- Why does water causes ionization of acids? This question might look dumb to some but I am wondering what special water has got that it ionizes acids (or maybe other species too).
- Why is there a release of heat? I have read that breaking of bonds is an endothermic process.