QUESTION 4

1. Calculate the...needed to produce a buffer with a pH of 6.50.(K_a of H₂CO₃ is4.3*10^–7)

   Directions: Type your answers only.You may scan your paper work and send it to me for partial creditif your answer is not correct.

   Your answer should look something like this:Ratio = (your answer)

2. QUESTION 6

3. The pH at the equivalence point during the titration of somesample of NH₃ by HCl is 5.20. What is the reason that pHat the equivalence point of a titration is not 7.0?

   		The pH at the equivalence point corresponds the excess of molesof HCl added.
   		The pH at the equivalence point corresponds the excess of molesof NH3.
   		The pH at the equivalence point corresponds to the hydrolysis ofNH4+.
   		The pH at the equivalence point corresponds to the hydrolysis ofCl–.

4. Some indicator has K_a = to 6.3*10^–9. Itsun-ionized form is yellow and its conjugate base is red. What colorwould a solution have at pH = 6.45?

   		Red
   		Orange
   		Green
   		Yellow

5. The sample of 25.0 mL of 0.0100 M HClO is titrated with 0.0200 MKOH. (a) Find the volume of 0.0200 M KOH needed toreach the equivalence point. (b) Calculate the pHat the equivalence point (K_b ofClO^– is3.0*10^–7).

   Which one of the following combinations cannot function as abuffer solution?

   6)

   		Na2HPO4 andNaH2PO4
   		NaHS and H2S
   		NaHSO4 and H2SO4
   		KHCO3 and H2CO3
   		NH3 and NH4I

6. b)

   Which of the following combinations would be the best to bufferthe pH of a solution at approximately 7?

   		Na2HPO4 and NaH2PO4(Ka = 6.23*10-8)
   		H3PO4 and NaH2PO4(Ka = 7.52*10-3)
   		Na3PO4 and Na2HPO4(Ka = 4.8*10-13)
   		KCN and HCN (Ka = 6.17*10-10)