Question

A 1.00 liter solution contains 0.24 M hypochlorous acid and 0.31 M sodium hypochlorite. If 0.160 moles of potassium hydroxide are added to this system, indicate whether the following statements are true or false. (Assume that the volume does not change upon the addition of potassium hydroxide.) A. The number of moles of HClO will decrease. B. The number of moles of ClO- will increase. C. The equilibrium concentration of H3O+ will remain the same. D. The pH will decrease. E. The ratio of [HClO] / [ClO-] will decrease.

Answer 1

Explanation:

When OH- (as in potassium hydroxide) is added, it reacts with the acid (HOCl) to reduce the amount of HOCl and increase the concentration of  sodium hypochlorite.

Potassium hydroxide will react with the hypochlorous acid to produce hypochlorite ions. In the process, some of the weak acid will be consumed, along with the added strong base.

This occurs as follows:

HClO(aq) + KOH(aq) → KClO(aq) + H2O(l)  

since water is formed, this maintains the pH.  Thus ...

A. The number of moles of HClO will decrease. - TRUE

B. The number of moles of ClO- will increase. - TRUE

C. The equilibrium concentration of H3O+ will remain the same. - TRUE

D. The pH will decrease. - FALSE

E. The ratio of [HClO] / [ClO-] will decrease. -TRUE. It will decrease as HClO goes down and ClO- goes up.