   # Tris(hydroxymethyl)aminomethane, commonly called TRIS or Trizma, is often used as a buffer in biochemical studies. Its buffering range is pH 7 to 9, and K b is 1.19 × 10 −6 for the aqueous reaction a. What is the optimal pH for TRIS buffers? b. Calculate the ratio [TRIS]/[TRISH + ] at pH = 7.00 and at pH = 9.00. c. A buffer is prepared by diluting 50.0 g TRIS base and 65.0 g TRIS hydrochloride (written as TRISHCl) to a total volume of 2.0 L. What is the pH of this buffer? What is the pH after 0.50 mL of 12 M HCl is added to a 200.0-mL portion of the buffer? ### Chemistry: An Atoms First Approach

2nd Edition
Steven S. Zumdahl + 1 other
Publisher: Cengage Learning
ISBN: 9781305079243

#### Solutions

Chapter
Section ### Chemistry: An Atoms First Approach

2nd Edition
Steven S. Zumdahl + 1 other
Publisher: Cengage Learning
ISBN: 9781305079243
Chapter 14, Problem 83AE
Textbook Problem
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## Tris(hydroxymethyl)aminomethane, commonly called TRIS or Trizma, is often used as a buffer in biochemical studies. Its buffering range is pH 7 to 9, and Kb is 1.19 × 10−6 for the aqueous reaction a. What is the optimal pH for TRIS buffers?b. Calculate the ratio [TRIS]/[TRISH+] at pH = 7.00 and at pH = 9.00.c. A buffer is prepared by diluting 50.0 g TRIS base and 65.0 g TRIS hydrochloride (written as TRISHCl) to a total volume of 2.0 L. What is the pH of this buffer?What is the pH after 0.50 mL of 12 M HCl is added to a 200.0-mL portion of the buffer?

(a)

Interpretation Introduction

Interpretation:

Tris(hydroxymethyl)aminomethane, commonly known as TRIS is given to be a commonly used buffer in the biochemical studies. Its buffering range (79) and its Kb is given. Various questions related to this are to be answered.

Concept introduction:

The relation between pH and pKa is given by Henderson-Hasselbach equation. According to this equation,

pH=pKa+log[Salt][Acid]

### Explanation of Solution

Explanation

Given

The Kb for TRIS is 1.19×106 .

The value of Ka is calculated by the formula,

Ka=KwKb

Where,

• Kw is the ionic product of water (1.0×1014) .
• Ka is the acid dissociation constant.
• Kb is the base ionization constant.

Substitute the value of Kw and Kb in the above expression.

Ka=1.0×10141.19×106=8.40×10-9_

Therefore, the Ka of TRIS is 8

(b)

Interpretation Introduction

Interpretation:

Tris(hydroxymethyl)aminomethane, commonly known as TRIS is given to be a commonly used buffer in the biochemical studies. Its buffering range (79) and its Kb is given. Various questions related to this are to be answered.

Concept introduction:

The relation between pH and pKa is given by Henderson-Hasselbach equation. According to this equation,

pH=pKa+log[Salt][Acid]

(c)

Interpretation Introduction

Interpretation:

Tris(hydroxymethyl)aminomethane, commonly known as TRIS is given to be a commonly used buffer in the biochemical studies. Its buffering range (79) and its Kb is given. Various questions related to this are to be answered.

Concept introduction:

The relation between pH and pKa is given by Henderson-Hasselbach equation. According to this equation,

pH=pKa+log[Salt][Acid]

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