As you complete these problems COPY the results into your lab notebook for use d

Question

As you complete these problems COPY the results into your lab notebook for use during your lab.
You need to create 100 mL of 0.25 M Tris-HCl (MW 157.6 g/mol) and 100 mL of 0.25 M Tris (MW 121.1 g/mol) (Ka = 8.32 x 10-9)

(a) How many grams of Tris-HCl do you need to weigh out?
  3.94 g
(b) How many grams of Tris-HCl do you need to weigh out?
  3.03 g

Complete the following table based on the use of the solutions created above to make the following ratios of buffer. (100mL of total buffer is used) (Give answers to 3 sigfigs):

Buffer # % Tris-HCL % Tris Molarity
Tris-HCL Molarity
Tris Predicted pH Buffer 1 0.75 0.25
Buffer 2 0.5 0.5
  
  
Buffer 3 0.75 0.25
  

Explanation / Answer

pKa of Tris base is 8.1 at 25 C.

Using Henderson Hasselback equation,

pH=pKa+ log[Tris]/[TrisHCl]

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