Question

1.) Consider a solution that is 0.10 M Acetic Acid (HC₂H₃O₂) and 0.10 M Sodium Acetate (NaC₂H₃O₂).
HC₂H₃O₂ + H₂O <---> C₂H₃O₂^- + H₃O⁺
a.) What happens if you add HCl (acid)?
b.) What happens if you add NaOH (base)?

2.) NH₃ + H₂O <---> NH₄⁺ + OH^-
If you add HCl, which way will it shift?

Answer 1

HC₂H₃O₂ + H₂O <---> C₂H₃O₂^- + H₃O⁺

(a) If you add HCl , this means that amount of H3O+ will increase in the solution. According to the Lechatelier principle, if you make any change to a equilibrium reaction, the reaction will try to minimize that change by shifting the position of the equilibrium.

If excess, H3O+ is present , equilibrium will shift towards left hand side (reverse direction)

(b) If a base is added, it will react with H+ to convert it to water. As H+ is removed from the reaction, it will try to produce more and more H3O+. So, the reaction equilibrium will shift towards right hand side (forward direction)

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As as above, adding H+ will remove OH- as water. Equilibrium will shift towards forward direction