Question

10. For an aqueous solution labeled "0.10 M potassium bromide," A) the pH is greater than 7. B) the pH = 13. D) the pH is less than 7. E) the pH = 7. C) the pH = 1. 11. For a 0.10 M solution of a weak acid, HA, with pKa = 6, which of the following is true? A) [HA] =[A-] B) [HA] does not equal [H3O+] C) [HA] =[H3O] D) [HA] = K E) [HA] = 0 12. The pKfor NH4 is 9.26. This expression refers to which of the following reactions? A. NH4+(ag) + OH-(ag) À NH3(aq) + H2O(ag) B. NH4+(aq) + H2O(1) NH3(aq) + H30(aq) C. H:0 (aq) + OH (ag) 2H2O(1) D. NH3(aq) +H30'(aq) + NH4+(aq) +H2O(1) E. NH3(aq) + H2O(1) NH4+(aq) + OH-(ag) 13. A solution is prepared by adding 100 mL of 0.4M hydrofluoric acid to 100 mL of 0.2 M sodium fluoride. Is this a buffer solution, and if so, what is its pH? A. It is a buffer, pH > PK.. B. It is a buffer, pH <PK. C. It is a buffer, pH = PK. D. It is a buffer, pH = Kb E. Since hydroformic acid is a strong acid, this is not a buffer. 14. Write the chemical equilibrium reaction for the auto-ionization of water. Label each chemical with its appropriate phase designation (solid. lig, gas, or aqueous). Also express the Kw for this process along with its value.

Answer 1

10) KBr is salt of strong acid and strong base. So if has pH = 7

(E) is correct option

11) HA -----> H⁺ + A^{​​​​​​-}

So [HA] doesn't equal to [H3O+] as it is weak acid

12)(B) is correct option

13) it is acidic buffer, pH = pKa + log[20/40)

pH = pKa + log(1/2) => pH = pKa - 0.30

pH <pKa (b) is correct

14) Auto -ionization of water

H2O(l) + H2O(l) <-----> H_{​​​​​​3}​​O^{​​​​+}(aq.)  + OH^​​​-(aq.)

Kw = [H3O⁺][OH^{​​​​​-}​​​​] = 1.0×10^-14