Chem 03-Bio 03 Final Exam Answer Key.pdf

Chem 03/Bio 03 NAME: Fall 2009 Species [CO,T* H.CO, KEY Final Exam (Part A 70 points) Always show your work! 1. Bicarbonate ion is the important pH buffer in the blood. (40 points) a. Fill in the table below for the carbonate anion [CO,]", the bicarbonate anion, (HCO,]" and carbonic acid, H,CO,. If resonance forms exist, just draw one resonance form. # of Valence Electrons 4 + 316) +2 = 24e 4+3/6) +1+1= 24e 2(1) + 4 + 3(0) = 24е- One reasonable Lewis structure. Indicate the formal Formal charge charges on each atom in your drawing. FC = valence electrons (unshared electrons + -2 (shared electrons)] 04,8 = 6- (6 + 8(2) = - 1 0 = 6-14+5(4) = 0 C = 4- (5(8)) = 0 Han -1 other adams IS O 956- (4+4(4))=0 08 - 4- (6+*(3)) - - 1 C=4- (½(2)) = 0 H= 1- (3(2)) = 0 All oxygens 0x = 6-(4+*(2)= 0 С = 4 -(K(8)= 0 = 1 - (4(2))= 0 b. Which of the species above can act as acids? Explain by writing down the chemical reaction that demonstrates it is an acid. carbonie aud 4C03 = 4* + 4c03 -2 H+ + bicarbonate (03) c. Which of the species above can act as bases? Explain by writing down the chemical reaction that demonstrates it is a base. bicarbonate HCO5 + H20 = 42C03 +оН - carbonate СО, + 120 4g + OH- d The pK,s for carbonic acid and bicarbonate are pKa, - 6.37 and pKaz - 10.3 respectively. Which one of the three species (carbonic acid, bicarbonate, or carbonate) is found in extremely low levels relative to the others in the blood at pH 7.4. Explain your ordering. NO CALCULATION NECESSARY Carbonate (CO,") lowest level (furthey eyes this 13) bicarbonate (HCOS=) highest level carbonic acid (HaCO,) highlevel, but less than HCO5 pH 7.Y of blood sits between pla, coronic seid that weakes MI09 (6.37) and play bicarbonate that destroys licos (10.3) c. Use the buffer equation below to predict the ratio of bicarbonate to carbonic acid in the blood at pH 7,4. Show your work Buffer: pKa = ph - log [A-JHA] relevant reaction is plar Ico, ta HOS+ H+ pKa,= 6.37 pka, * 6.4 64 = 7.4 - 10g LAZ/14 - 1=- 10g */HA Ratio 15 log A/HA 10 = 7A = 10 10 4G- to 1 H2O3 f. If you exercise hard, and release lots of H* into your blood through lactic acid, how does your body adjust its respiration rate to maintain the ph of your blood close to 7.4? Explain. A person wall exhale more rapidly breathe more rapidly to get red of Car 420 + C02 H6•CO lungs 16 + C02 Chem 03/Bio 03 Fall 2009 Oxygen transported by the blood is eventually turned into water during metabolism. Here is the overall reaction by which this happens, though in the body at least 18 enzymes and five electron transfer complexes participate in the transformation (TAKE MORE BIOCHEM TO INVESTIGATE). 602 + glucose = 6H20 + 6C02 Looking only at the conversion of oxygen to water, decide if this is a redox reaction or not by determining the effective oxidation state of the oxygen atoms in the reactant (Oz) and the product (H,O). If your answer is yes, is the oxygen oxidized or reduced? (Electronegativity of 0 and H are 3.5 and 2.1 respectively) Effective oxidation state = Valence Electrons - [unshared electrons + shared cicctrons from bonds made with less electronegative elements) oxid stale = 0 of oxid state = -2 effordstate: 6-(4+4) = -2 Yes this I aredox, oxygen must gain elections to bereduced h. How would I prepare 10.00 ml of a 50.00 M stock of sodium carbonate from a stock of 25.62 mM? Show your work M - moles/liter; mM = 10' M; uM= 10°M; 1 mL = 1 x 10°L Stock (25.42x10 34) (V) = (50.00x15 ° M(10.00 mL) V, = 0.02000 mL 20.00 pL To prepare dilution, take 20, 00ul of stock solution and dilute to 10.00mL with water