Biochemistry M2 Exam Questions and Answers 100% Pass

Biochemistry M2 Exam Questions and Answers 100% Pass The pH of a solution of 0.0010 M NaOH is: 11 (Kw=[H+][OH-] = 1.0 x 10-14; [H+][0.0010] = 1.0 x 10-14 [H+]=1.0 x 10-11; pH=-log[1.0 x 10-11]=11) Water is a unique molecule. Which of the following contributes to water's unique place in the chemical world? All of the answers are correct The bent shape of water is due to ______________. The unshared electron pairs on the oxygen atom Which diagrams correctly represent a hydrogen bond? A and D The H+ concentration of a solution is 1.2 x 10-3 M. What is the pH? 2.92 If the Ka of an acid is 5.63 x 10-3, what is the pKa? 2.25 ([pKa = -log(5.63 x 10-3) = 2.25]) List the acids in DECREASING order of strength (strongest to weakest): Nitrous acid (Ka = 4.0 x 10-4); acetic acid (Ka = 1.7 x 10-5); phosphoric acid (Ka = 7.3 x 10-3) Phosphoric acid, nitrous acid, acetic acid Elemental iodine (I2) is a solid at room temperature. What is the dominant attractive force that exists between I2 molecules in the solid? London forces Which one of the following molecules can form a hydrogen bond? (A.) HBr (B.) HCl (C.) NH3 (D.) CH4 (E.) H2 C. NH3 A hydrogen bond can form between a hydrogen atom bonded to oxygen, O-H, and ________. N In a bond between P and Cl, there exists a difference in electronegativity resulting in partial positive and partial negative charges. If a dipole arrow were added to this structure, which way would the arrow point? The arrow points from N toward Br The following reaction occurs in glues purchased from hardware stores. Customers use this product to glue plastic together. Epoxy (l) + hardener (l) ⟶ Glue (s) + heat given off What is the sign (+ or -) of the change in Δ G and Δ H? Δ G is (-) and Δ H is (-) Which of the following is the free-energy change of a reaction? Δ G Which of the following is the change in entropy of a reaction? None of the above A Which buffer system is used by the renal system to maintain pH balance? Bicarbonate buffer system A buffer can neutralize acid and base within a certain limit. We say that this is its: Buffer capacity Is a pH of 8.36 acidic, neutral, or basic? Basic The "ion product" is equal to what value? 1.0 x 10-14 In equilibrium constant expressions, the concentration is expressed in units of _______ as indicated the by the brackets [ ]. Molarity A pH = 5.0 indicates a concentration of OH- (in M) of __________. 10^-9 The lysosome has a pH of 5.0. Which of the following weak acids would best work to buffer at pH 5.0? Propionic acid Which of the following compounds would not be soluble in water? Wax The oxygen in water has what type of hybridization? C. sp3 Four identical molecules dissolve in water. Each molecule contains both a polar portion and nonpolar portion of structure. The four molecules interact in such a way that the nonpolar sections align. This is an example of the _________. Hydrophobic effect (Short Response) How does the strength of a hydrogen bond compare to the strength the London Force? Also, how about the strength of a hydrogen bond compare to a dipole-dipole force? Briefly comment on these differences. Hydrogen bond strength is between 12-16 kcal; London force is 1 Kcal; dipole-dipole bond is 0.5-2.0 kcal. Hydrogen bonds are the strongest non-covalent force. (Short Response) The weak acid HX has the following equilibrium reaction with 0.64M HX, 0.55M X-, and 0.55M H+. Calculate the Ka for this hypothetic compound. Show your work. HX = H+ + X- Ka= [X-][H+]/ HX; Ka = 0.55 x 0.55 / 0.64; Ka = .4727 (no units) (Short Response) Use the general ionization equation for a weak acid to show how a buffer resists changes to the addition of Acid (H+). HA = A- + H+ The conjugate base A- reacts with added H+ to form weak which neutralizes the acid and maintains the pH. (Fill in the blanks) At cool temperatures, water vapor turns into liquid water releasing heat in the process. Fill in the missing blanks, below, regarding this process. Please identify your answers by writing "A." then your answer, "B" then your answer, and so forth. "The free-energy change, Δ G, has a _____A______ value (choose "+" or "-"). The enthalpy change, __B__ (fill in symbol), has a ___C_____ value (choose "+" or "-"). The _____D______change, (Δ S) has a ______E_____ value (choose "+" or "-")." A) - B) Δ H C) -D) entropy E) - (Short Response) What is the hydrophobic effect and how does a clathrate help explain this phenomenon? The hydrophobic effect explains how biological molecules form and interact. When molecules with both a nonpolar and polar regions dissolve in water, the nonpolar regions pack together. Water orders itself around the hydrophobic portion of the nonpolar regions in a cage structure, called a clathrate, forming bonds with itself and also permit the nonpolar regions to be dissolved.