Question

How many of the following responses are true?

1. When dissolved in water, the third dissociation of H3PO4 will not produce a significant amount of the H+ ion

2. Successive Ka values for polyprotic acids become larger, and are therefore more important in determining the pH of a solution

3. The % dissociation of H3PO4 is greater than that of a strong acid because there are more moles of protons in the polyprotic acid

4. HCN is a strong acid and will dissociate completely in water

5. HI is a strong acid and will dissociate completely in water

obviously, i know that 4 is false and 5 is true but i dont know about 1,2,3.

Answer 1

Answer – We are given, the statements and need to find out the true statements.

1)True - When dissolved in water, the third dissociation of H3PO4 will not produce a significant amount of the H+ ion, since the third ionization constant for H₃PO₄ is too small and it is not affect much more on the H⁺, so this statement is true.

2) False -Successive Ka values for polyprotic acids become smaller than larger, and are therefore more important in determining the pH of a solution.

3) False- Since the % dissociation of H3PO4 is depends on the dissociated moles by initial moles and strong acid % dissociation of H3PO4 or strong acid are same at same initial concentration.

4) False- HCN is weak acid, so it is not dissociating completely in water.

5) Ture- HI is strong acid, since it dissociated completely.