Question

Given the following list of common buffer systems available to you in your lab, how would you prepare a system with a pH of 7.70?

HEPES pKa = 7.56

HEPPS pKa = 7.96 TRIS·

HCl pKa = 8.07

A.Using HEPES solution, add NaOH to raise the pH to 7.70

B.Using HEPES solution, add HCl to lower the pH to 7.70

C.Using HEPPS solution, add HCl to lower the pH to 7.70

D.Using HEPPS solution, add NaOH to raise the pH to 7.70

E.From solid constituents of TRIS-HCl and TRIS*Na+, dissolve in solution, and raise to desired pH with NaOH.

In the titration of a weak base with a strong acid titrant, past the equivalence point, treat the system as:_______________.

A.A weak acid

B.A diluted strong acid

C.A weak base

D.A diluted strong base

E.A buffer

Answer 1

Answer for first question.

From solid constituents of TRIS-HCl and TRIS*Na+, dissolve in solution, and raise to desired pH with NaOH.

Explanation : By mixing appropriate quantities of Tris Base and Tris HCl, stock buffers of various pHs may be prepared.

Answer for second question.

In the titration of a weak base with a strong acid titrant, past the equivalence point, treat the system as:A dilute strong acid

Option B is the correct answer.

As past the equivalence point solution contain conjugate acid of weak base and extra added strong acid so system will treat as dilute strong acid.