MOPS is a compound commonly used to prepare buffer suitable for biochemistry and molecular biology

experiments. Use the questions below to explore the practical use of MOPS in the lab.

a$.$ Use the internet to find the structure of MOPS. Paste or draw this structure.

b$.$ Circle in red the atoms that can accept a proton. Circle in blue the ionizable proton$($s$)$

present in the molecule

c$.$ Determine which atom the proton$($s$)$ is most likely attached. Redraw the structure of

MOPS if necessary. Justify your choice$($s$)$ using your knowledge of organic chemistry.

d$.$ If you dissolve MOPS in water, will the solution be alkaline or acidic? Justify your

answer.

e$.$ The pKa of MOPS is $7\mathrm{.}20.$ Draw the equilibrium involved in the dissociation of the proton.

f$.$ Suppose you dissolve $0\mathrm{.}200$ mol of MOPS in $1\mathrm{.}00$ L of water. Calculate the pH of the

solution.

g$.$ Use the pKa of MOPS to determine the ratio $[$A$-]/[$HA$]$ at pH $6\mathrm{.}95.$

h$.$ If you have $0\mathrm{.}200$ mol of MOPS dissolved in water, would you add NaOH or HCl to reach

a pH of $6\mathrm{.}95?$ And how many moles of the acid or base would you need to add?

i$.$ If you use a $100$ mM MOPS buffer at pH $6\mathrm{.}95$ for a biochemical reaction which produces

a maximum of $10$ mM H$+,$ which pH would you predict at the end of the reactio