Biochem Module 2 Questions and Answers Graded A

Biochem Module 2 Questions and Answers Graded A What is the shape of water? Bent. The bond angle is 104.5 degrees. What is autoionization, and how is it important for water? Autoionization is the ability of a compound to react with itself to form ions. One water molecule reacts with a second molecule to form two ions: H3O+ and OH-. These ions exist in small amounts in pure water and influence the chemistry of water. Name the three non-covalent forces discussed in this module 1. Dipole-dipole forces, 2. Hydrogen bonding, and 3. London dispersion forces What type of non-covalent interaction is known as the strongest dipole-dipole force? .hydrogen bonds. Would the following be a hydrogen donor or acceptor? Or both? .Only a hydrogen acceptor due to the electrons on the oxygen. It is not a hydrogen donor because the electrons are bonded to a carbon. How does the strength of London forces change with increasing molecular weight? Explain briefly. As molecular weight increase, the strength of London forces also increase. This is due to the increased number of electrons in larger molecules. The larger number of electrons creates the potential of stronger temporary dipoles. Calculate the pH of solution containing 0.12 M of OH-. pH = 13.08 If a solution contains 0.00023M of H+, then what is the OH- concentration? 4.35 X 10-11 M OH- If a solution contains 1.67 x 10-8 M OH-, then what is H+ concentration? 5.99 x 10-7 M H+ or 6 X 10-7M A solution contains H+ at a concentration of 1.67 x 10-6 M. Is the solution acidic, basic, or neutral? Explain briefly. Acidic. The pH = 5.77, which is acidic. Students should use the pH scale Table in Module 2 to determine this. What is the concentration, in M, of water as a pure liquid? 55.5 mol/L Define Keq and Kw. Keq is the equilibrium constant. Numerically, it is equal to the concentrations of equilibrium products (in M) multiplied together over the concentration of equilibrium reactants multiplied together. Kw is called the ion product. It is, essentially, the Keq for water that is equal to 1.0 x 10-14; the formula is: Identify the acid, conjugate base, and proton in the following reaction. Write the chemical species and identify it. HCOOH is the weak acid; H+ the proton; HCOO- L a T e X :⟶ conjugate base A buffer system has a pKa of 8.5. What is its effective buffering range? 7.5 to 9.5 A buffer system has [H+] = 1.2 x 10-6, [A-] = 1.2 x 10-6, and [HA] = 3.2 x 10-5. What is its corresponding Ka value? Ka = 4.5 x 10-8 (no units) Weak acid A has a pKa of 3.2, while weak acid B has a pKa of 5.6. Is Weak acid A or B the stronger of the two? Weak acid A is stronger because a smaller pKa indicates a stronger acid. Ice melts at room temperature. What is the sign for Δ G in this reaction? (-) negative. The reaction happens spontaneously. Butane torch combusts in the air by the following reaction: C4H10 (l) + 6.5 O2 (g) ⟶ 4 CO2 (g) + 5 H2O (g) What is the sign (+ or -) of Δ G, Δ H, and Δ S in this reaction? G(-) happens as written, L a T e X : Δ H is (-) gives off heat, and L a T e X : Δ S is (+) because more disordered gases are produced. What the role of ATP in helping non-spontaneous reaction occur? It provides a source of energy to assist the reaction. ATP breakdown has large negative value.