Problem 24
MATHEMATICAL Calculate the hydrogen ion concentration, \(\left[\mathrm{H}^{+}\right]\) for each of the following materials: (a) Saliva, pH 6.5 (b) Intracellular fluid of liver, pH 6.9 (c) Tomato juice, pH 4.3 (d) Grapefruit juice, pH 3.2
Problem 26
Define the following: (a) Acid dissociation constant (b) Acid strength (c) Amphipathic (d) Buffering capacity (e) Equivalence point (f) Hydrophilic (g) Hydrophobic (h) Nonpolar (i) Polar (j) Titration
Problem 40
A catalog in the lab has a recipe for preparing 1 L of a TRIS buffer at \(0.0500 \mathrm{M}\) and with pH 8.0 : dissolve \(2.02 \mathrm{g}\) of TRIS (free base, \(\mathrm{MW}=121.1 \mathrm{g} / \mathrm{mol}\) ) and \(5.25 \mathrm{g}\) of TRIS hydrochloride (the acidic form, \(\mathrm{MW}=157.6 \mathrm{g} / \mathrm{mol}\) ) in a total volume of 1 L. Verify that this recipe is correct.
Problem 47
BIOCHEMICAL CONNECTIONS You need to carry out an enzymatic reaction at \(\mathrm{pH} 7.5 .\) A friend suggests a weak acid with a \(\mathrm{p} K_{\mathrm{a}}\) of 3.9 as the basis of a buffer. Will this substance and its conjugate base make a suitable buffer? Why or why not?
Problem 53
Define buffering capacity. How do the following buffers differ in buffering capacity? How do they differ in pH? Buffer a: \(0.01 \mathrm{M} \mathrm{Na}_{2} \mathrm{HPO}_{4}\) and \(0.01 \mathrm{MNaH}_{2} \mathrm{PO}_{4}\) Buffer b: \(0.10 \mathrm{M} \mathrm{Na}_{2} \mathrm{HPO}_{4}\) and \(0.10 \mathrm{MNaH}_{2} \mathrm{PO}_{4}\) Buffer \(c: 1.0 M \mathrm{Na}_{2} \mathrm{HPO}_{4}\) and \(1.0 \mathrm{MNaH}_{2} \mathrm{PO}_{4}\)
Problem 54
If you wanted to make a HEPES buffer at \(\mathrm{pH} 8.3,\) and you had both HEPES acid and HEPES base available, which would you start with, and why?
Problem 57
Many of the buffers used these days, such as HEPES and PIPES, were developed because they have desirable characteristics, such as resisting pH change with dilution. Why would resisting pH change with dilution be advantageous?
Problem 58
Another characteristic of modern buffers such as HEPES is that their pH changes little with changes in temperature. Why is this desirable?
