* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download KEY Final Exam Review - Iowa State University
Asymmetric induction wikipedia , lookup
Electrolysis of water wikipedia , lookup
Acid dissociation constant wikipedia , lookup
Nucleophilic acyl substitution wikipedia , lookup
Multi-state modeling of biomolecules wikipedia , lookup
Marcus theory wikipedia , lookup
Chemical thermodynamics wikipedia , lookup
Electrochemistry wikipedia , lookup
Hydrogen-bond catalysis wikipedia , lookup
Supramolecular catalysis wikipedia , lookup
Photoredox catalysis wikipedia , lookup
Stille reaction wikipedia , lookup
Woodward–Hoffmann rules wikipedia , lookup
Acid–base reaction wikipedia , lookup
Process chemistry wikipedia , lookup
Determination of equilibrium constants wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Thermometric titration wikipedia , lookup
Equilibrium chemistry wikipedia , lookup
Hydroformylation wikipedia , lookup
Chemical reaction wikipedia , lookup
Ultraviolet–visible spectroscopy wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
George S. Hammond wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
Strychnine total synthesis wikipedia , lookup
Click chemistry wikipedia , lookup
Reaction progress kinetic analysis wikipedia , lookup
Rate equation wikipedia , lookup
Transition state theory wikipedia , lookup
Final Exam Review: 1 Supplemental Instruction Iowa State University Leader: Olivia Course: Chem 178 Instructor: Bonaccorsi Date: 1.What is the rate-determining step and why is it important? Rate Determining step is the slowest step in the elementary steps. It looks the most like the rate law. The following data were measured for the reaction of BF3(g)+NH3(g) →F3BNH3(g): Experiment [BF3](M) [NH3](M) Initial Rate (M/s) 1 0.250 0.250 0.2130 2 0.250 0.125 0.1065 3 0.200 0.100 0.0682 4 0.350 0.100 0.1193 5 0.175 0.100 0.0596 a. What is the rate law for the reaction? k[BF3][NH3] seen by exp 1&2;4&5 b. What is the overall order of the reaction? 2 c. Calculate the Rate constant with proper units. Using exp 1 k=(0.2130)M/s/(0.250M)(0.250M)=3.41M-1s-1 could use any of the five to calculate this. kave=3.408M-1s-1 d. What is the rate when [BF3]=0.100M and [NH3]=0.500M? rate=3.408M-1s1*(0.100M)*(0.500M)=0.170M/s 2a. Write the rate law for a reaction between A, B, and C that is the first order in A, zero order in B, and second order in C. k=[A][C]2 b. What happens to the rate when [A] doubles and all other concentrations stay the same? They are proportional therefore rate would double c. What happens to the rate when C is tripled and all other concentrations stay the same? Rate increases by a factor of 32 or 9 d. By what factor does the rate change if all three are tripled? [A]=3 [B]=0 [C]=2 so… 3*32=27 e. By what factor does the rate change if all three are cut in half? (1/2)*(1/2)2=1/8 3. Write the mass action expression for the reaction C(s) + CO2 (g) 2CO (g) K= [CO]2/[CO2] 4. Find the Kc value for the overall reaction given: 1) CaO (s) + H2 (g) Ca (s) + H2O (g) K1=67 2) CaO (s) + CO (g) Ca (s) + CO2 (g) K2=490 overall: H2 (g) + CO2 (g) CO (g) + H2O (g) Kc = K1/K2 = [H2O][CO]/[H2][CO2] = 67/490 = 0.14 5. Label if the following will favor products or reactants K>1 products 1060 Hixson-Lied Student Success Center 515-294-6624 [email protected] http://www.si.iastate.edu K<1 reactants K>Q products K<Q reactants CH16 6. For Nitrous Acid, HNO2 the Ka = 4.5*10-4. What is the Kb value for the nitrite ion, NO2-? Kb=Kw/Ka = (1.0 x 10^-14)/(4.5 x 10^-4) = 2.2 x 10^-11. 7. Calculate the pH of 0.1M HNO3 at 298 K. HNO3 is a strong acid pH = -log(0.1) = 1 8. Calculate the pH of 0.1 M HNO2 at 298 K. Ka=4.5x10-4 HNO2 H2O I 0.1 C -x E 0.1-x - H3O 10-7 +x 10-7+x NO2 +x +x 4.5*10-4 = x*(10-7+x)/(0.1-x) = x2/0.1 x = 6.49*10-3 M pH = -log (6.49*10-3 M) = 2.19 9. Initially 0.035 moles of SO2, 0.5 moles of SO2Cl2, and 0.08 moles of Cl2 are combined in a 5liter flask. What is the value of Q and which direction will the reaction proceed to establish equilibrium? SO2Cl2 (g) ⇄ SO2 (g) + Cl2 (g) Kc = 0.078 SO2Cl2 SO2 Cl2 0.5/5 0.35/5 0.08/5 0.1M 0.007M 0.016 Q = [(0.016)(0.007)]/(0.1) = 1.12*10-3 K>Q moves towards products 10. Aspirin has a pKa of 3.4. What is the ratio of A¯ to HA in: (a) the blood (pH = 7.4) (b) the stomach (pH = 1.4) General comment about the solutions: You have to find the ratio between A¯ and HA so the concentrations are not needed Solution to part (a): pH = pKa + log [A¯] / [HA] 7.4 = 3.4 + log [A¯]/ [HA] 7.4 - 3.4 = 4 = log [A¯]/ [HA] 104 = 10000 = [A¯]/ [HA] Solution to part (b): 1.4 = 3.4 + log [A¯]/ [HA] 1.4 - 3.4 = - 2.0 = log [A¯]/ [HA] 10-2 = 0.01 = [A¯]/ [HA] 11. What is the hydroxide ion concentration in a solution that has a pOH of 5.70? 5.70 = - log [OH-] -5.70 = log[OH-] [OH ] = 10-5.70 = 2.00 x 10-6 M 12. 32.00 g of sodium hydroxide were dissolved in 250.0 mL of solution to prepare the titrant. 25.00 mL of sulfuric acid were titrated with above titrant. It took 16.00 mL of sodium hydroxide solution to titrate to the end point. What is the molarity of the sulfuric acid? Solution: 1) Determine molarity of NaOH: MV = grams divided by molar mass (x) (0.2500 L) = 32.00 g / 40.00 g/mol x = 3.200 M 2) Determine moles NaOH in 16.00 mL of 3.200 M solution: moles NaOH ⇒ (3.200 mol/L) (0.01600 L) = 0.05120 mol 3) Determine moles of H2SO4 that react: 2NaOH + H2SO4 ---> Na2SO4 + 2H2O The molar ratio between NaOH and H2SO4 is 2:1 Therefore, 0.05120 moles of NaOH will neutralize 0.02560 moles of H2SO4 4) Calculate molarity of H2SO4 solution: 0.02560 mol / 0.02500 L = 1.024 M 13. H2S + NO3¯ ---> S8 + NO Solution: 1) The unbalanced half-reactions: H2S ---> S8 NO3¯ ---> NO 2) balance each half-reaction: 8H2S ---> S8 + 16H+ + 16e¯ 3e¯ + 4H+ + NO3¯ ---> NO + 2H2O 3) Make the number of electrons equal: 24H2S ---> 3S8 + 48H+ + 48e¯ <--- multiplied by a factor of 3 48e¯ + 64H+ + 16NO3¯ ---> 16NO + 32H2O <--- multiplied by a factor of 16 Note that 16 and 3 have no common factors except 1, so both 16 and 3 had to be used to obtain the lowest common multiple of 48 for the number of electrons. 4) Add: 24H2S + 16H+ + 16NO3¯ ---> 3S8 + 16NO + 32H2O Comment: removing a factor of 8 does look tempting, doesn't it? However, the three in front of the S8 (or the five in the next example) makes it impossible. Also, note that duplicates of 48 electrons and 48 hydrogen ions were removed. 14. In the reaction 2 NO2(g) _ N2O4(g) the initial concentration of NO2 was 0.250 M and N2O4 was 0.000 M. At equilibrium, the concentration of N2O4 was measured as 0.0133 M. (a) Calculate the equilibrium concentration of NO2 (b) Calculate Kc. 15. What is the pH and chemical reaction of a solution containing 0.25 M HCO3- and 0.34 M Na2CO3? Ka(HCO3-)= 5.6x10-11 HCO3- + H2O equil CO32- + H3O+ 0.25 0.34 pH = pKa +log (A-/HA)= -log (5.6x10-11) + log (0.34/0.25) = 10.39 CH19 16. Is the following reaction spontaneous at 25 C under the following conditions: N2 (g) + O2 (g) 2NO (g) Nitrogen and oxygen have a pressure of 1 atm and nitrogen oxide has a pressure of 4 atm at some point during the reaction. (delta)Go=173.1 kJ. Delta G = Delta G* + RTlnQ Q = P2NO /(PN2*PO2) = 42/(1)(1) = 16 Delta G = 173.1 + 8.314*10^-3 (298)ln(16) Delta G = 180 kJ Not Spontaneous. 17. For each pair, which molecule has a greater entropy? a. CO2 (s) or CO2 (l) b. NH3 (l) or NH3 (g) c. Pure magnesium at 0K or 200K CH20 18. Calculate the cell potential for a cell operating with the following reaction at 25o C, in which [MnO4 -] = 0.010 M, [Br- ] = 0.010 M, [Mn2+] = 0.15M and [H+ ] = 1.0 M. 2 MnO4 - (aq) + 10 Br- (aq) + 16 H+ (aq) 2Mn2+(aq) + 5Br2(l) + 8H2O(l) 19. Consider the reaction 3CH4 (g) C3H8 (g) + 2H2 (g) a. Using ΔG0 of C3H8 = -23.47kJ and ΔG0 of H2 = 0 and ΔG0 of CH4 = -50.8, calculate, at 298K, ΔG0 b. Calculate delta G at 298K if the reaction mixture consists of 40.0 atm of CH4, 0.0100atm of C3H8, and 0.0180 atm of H2. 20. For a certain chemical reaction, delta H knot = -35.4 kJ and detla S knot = -85.5 J/K a. Is the reaction endothermic or exothermic? b. Does the reaction lead to an increase or decrease in the randomness or disorder of the system? c. Calculate delta G knot for the reaction at 28 degrees C d. Is the reaction spontaneous at that temperature under standard conditions?