Question

Buffers that are based on 3-morpholinopropanesulfonic acid (MOPS) are often used in RNA analysis. The useful pHrange of a MOPS buffer is $\mathbf{6}\mathbf{.}\mathbf{5}$ to role="math" localid="1663323468024" $\mathbf{7}\mathbf{.}\mathbf{9}$. Estimate the role="math" localid="1663323276603" ${\mathbf{K}}_{\mathbf{a}}$of MOPS.

Short answer

The value of MOPS is$6\times {10}^{-8}$.

Step-by-step solution

Definition of Concept.

Capacity: The amount of heat energy required to raise the temperature of a body by a certain amount is known as heat capacity. The amount of heat in joules required to raise the temperature 1 Kelvin is known as heat capacity (symbol: C) in SI units.

Calculate the Ka of MOPS.

Considering the given information:

The pH range of 3-morpholinepropanesulfonic acid (MOPS) is $6.5$to$7.9$.

From the given pH range, calculate the average role="math" localid="1663323531566" ${\text{pK}}_a$.

Average role="math" localid="1663323618817" ${\text{pK}}_a$(center of range)

$$\begin{gathered} =(7.9+6.5)/2 \\ =7.2 \end{gathered}$$

Calculate the role="math" localid="1663323643490" ${\text{K}}_a$value from ${\text{pK}}_a$value,

Average${\text{pK}}_a\text{=7.2}$

$\begin{array}{c}{\mathrm{K}}_{\mathrm{a}}={10}^{-7.2}\\ =6.3095734\times {10}^{-8}\\ =6\times {10}^{-8}.\end{array}$

Therefore, the ${\mathrm{K}}_a$value of MOPS is $6\times {10}^{-8}$.