Chapter 2

Water is said to be polar but uncharged. How is it possible? \(4\)

Why are weak bonds important in biochemistry? \(4\)

What are the common types of weak bonds important in biochemistry? How does water affect these bonds? \(4\)

. In liquid water, each molecule is hydrogen bonded to approximately 3.4 molecules of water. What effect would freezing water have on the number of hydrogen bonds? Heating water?

What is an electronegative atom, and why are such atoms important in biochemistry? \(/5\)

Define the hydrophobic effect. 5

How does the Second Law of Thermodynamics allow for the formation of biochemical order?

If an aqueous solution has a hydrogen ion concentration of \(10^{-5} \mathrm{M},\) what is the concentration of hydroxyl ion? \(6\)

If an aqueous solution has a hydroxyl ion concentration of \(10^{-2} \mathrm{M},\) what is the concentration of hydrogen ion? 6

Using the Henderson-Hasselbalch equation, show that, for a weak acid, the \(\mathrm{p} K_{\mathrm{a}}\) is the \(\mathrm{pH}\) at which the concentration of the acid equals the concentration of the conjugate base. \(6\)

What is the relation between the \(\mathrm{p} K_{\mathrm{a}}\) of an acid and the strength of the acid? \( 6\)

The \(\mathrm{p} K_{\mathrm{a}}\) of acetic acid is 4.76 and the \(\mathrm{p} K_{\mathrm{a}}\) of trichloroacetic acid, which is used to remove warts, is 0.7. Calculate the dissociation constant of each acid. Which is the stronger acid? \(6\)

For an acid HA, the concentrations of HA and \(\mathrm{A}^{-}\) are 0.075 and \(0.025,\) respectively, at \(\mathrm{pH} 6.0 .\) What is the \(\mathrm{p} K_{\mathrm{a}}\) value for \(\mathrm{HA} ? 6\)

A dye that is an acid and that appears as different colors in its protonated and deprotonated forms can be used as a pH indicator. Suppose that you have a \(0.001 \mathrm{M}\) solution of a dye with a \(\mathrm{p} K_{\mathrm{a}}\) of \(7.2 .\) From the color, the concentration of the protonated form is found to be \(0.0002 \mathrm{M} .\) Assume that the remainder of the dye is in the deprotonated form. What is the \(\mathrm{pH}\) of the solution? \( {6}\)

An acid with a \(\mathrm{p} K_{\mathrm{a}}\) of 8.0 is present in a solution with a pH of 6.0. What is the ratio of the protonated to the deprotonated form of the acid?\( {6}\)

. Calculate the concentration of acetic acid and acetate ion in a \(0.2 \mathrm{M}\) acetate buffer at \(\mathrm{pH}\) 5. The \(\mathrm{p} K_{\mathrm{a}}\) of acetic acid is \(4.76 . \%\) 6

You are working in a high-powered clinical biochemistry lab. The chief scientist rushes in and announces, "I need \(500 \mathrm{ml}\) of \(0.2 \mathrm{M}\) acetate, \(\mathrm{pH}\) 5.0. STAT! Who is the best and brightest in this room?" All eyes turn toward you. You have solid anhydrous sodium acetate \(\left(\mathrm{MW}=82 \mathrm{g} \mathrm{mol}^{-1}\right)\) and a solution of \(1 \mathrm{M}\) acetic acid. Describe how you would make the buffer. \(\quad 6\)

Following a bout of intense exercise, the \(\mathrm{pH}\) of the exerciser's blood was found to be \(7.1 .\) If the \(\mathrm{HCO}_{3}^{-}\) concentration is \(8 \mathrm{mM},\) and the \(\mathrm{p} K_{\mathrm{a}}\) for \(\mathrm{HCO}_{3}^{-}\) is \(6.1,\) what is the concentration of \(\mathrm{CO}_{2}\) in the blood? \({6}\)