What is the effect on the concentration of hydrofluoric acid, hydronium ion, and fluoride ion when the following are added to separate solutions of hydrofluoric acid? (a) HCl (b) KF (c) NaCl (d) KOH (e) HF

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Chemistry

Eduardo Rice

8 September, 10:08

What is the effect on the concentration of hydrofluoric acid, hydronium ion, and fluoride ion when the following are added to separate solutions of hydrofluoric acid? (a) HCl (b) KF (c) NaCl (d) KOH (e) HF

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Gromit · Answer 1

Whenever a system in equilibrium gets disturbed, the adjustment of the system is done in such a manner that the effect of the change gets nullified, this is known as Le Chatelier's Principle. Let us consider that if a reaction present in an equilibrium gets disturbed by changing pressure, concentration, pressure, or other things, then the reaction will move in such a manner so that it can attain the equilibrium again.

Based on the given question, the equation is:

HF (aq) + H2O (l) ⇒ H3O + (aq) + F - (aq)

a) When HCl is added, the dissociation of HCl takes place within the water to give rise to Cl - and H3O + ions. One can witness an overall enhancement in the H3O + ions concentration and the shifting of the equilibrium will take place in the backward direction based on the Le-Chatelier's principle. Thus, on adding HCl, the concentration of H3O + and F - ions decreases, and the concentration of HF increases.

b) When the addition of a strong electrolyte like KF is done, the dissociation of KF is done into the F - and K + ions. Thus, with the overall enhancement in the F - ions concentration, the shifting of equilibrium will take place in the backward direction based on the Le-Chatelier's principle. Thus, with the addition of KF, the concentration of H3O + and F - ions decreases, and HF increases.

c) With the addition of strong electrolytes like NaCl in the solution, the dissociation of NaCl takes place into the Cl - and Na + ions. With the addition of NaCl, the equilibrium is not disturbed as the ions exhibit no influence on the given equilibrium reaction. Thus, the concentration of H3O+, HF, and F - ions remains unmodified.

d) With the addition of KOH, the dissociation of KOH takes place into K + and OH - ions. Based on Le-Chatelier's principle, the equilibrium will shift in the forward direction as the produced OH - ions will consume the hydronium ions. Therefore, the concentration of H3O + and F - ions increases, while the concentration of HF decreases.

e) With the addition of HF, that is, a weak acid, the equilibrium will move in the forward direction to counter the change as the concentration of reactant increases. Therefore, the H3O + and F - ions decreases, and the concentration of HF increases.