Question

Consider a buffer solution consisting of CH3NH3Cl and CH3NH2. Which of the following statements are true concerning this solution?
(Ka for CH3NH3+ = 2.3 x 10 -11).
1. A solution consisting of 0.1 M CH3NH3Cl and 0.1 M CH3NH2 would be a more effective buffer than one containing 1.5 M CH3NH3Cl and 1.5 M CH3NH2
2. Adding more [CH3NH3+ to the initial buffer solution will increase the pH.
3. If [CH3NH3+] >[CH3NH2], then pH is larger than the pKa value.
4. If [CH3NH3+] < [CH3NH2], then the [H+] is larger than the Ka value.
5. If [CH3NH3+] = [CH3NH2], then pH = 7.00.
6. If NaOH were added to the initial buffer solution, then the [CH3NH3+] would decrease.

Answer 1

I would go with 2 as true.
Use pH = pKa + log (acid)/(base) to evaluate the other statements.