Academic Integrity Pledge: In keeping with Creighton University’s ideals and with the Academic Integrity Code, I pledge that this work is my own and that I have neither given nor received inappropriate assistance in preparing it.
Signature: / Chemistry Student Number: ______
Instructions:Show all work whenever a calculation box is provided! Write legibly. Include units whenever appropriate. You will receive credit for how you worked each problem as well as for the correct answer. If you need more space, you may use the back of the datasheet provided — Write: “See data sheet” in the answer box – then write your name on the data sheet. On your desk you are allowed only pencils (but no pencil pouch), an eraser, and a non-programmable calculator without a slipcover. Backpacks, bags, and purse-like items must be stored on the floor the front section of the room. Cell phones must be silent and placed in your backpack/bag/purse – not in your pocket.
1. Propylene glycol, shown here,is used as a safe alternative to traditional antifreeze. Its main advantage is that it is not as poisonous to pets as traditional antifreeze.
1a. (2 pts) Add the correct number of electron pairs wherever needed to the structure above.
1b. (1 pt) Knowing that propanol is miscible with water, is propylene glycol also miscible with water? Circle Yes or No or Can not predict
1c. (1 pt) What is the name of the functional group on the left carbon in the figure? Print. Spelling counts.2. (4 pts) Circle all of the intermolecular forces that these molecules exhibit.Hint: There may be more than one. Circle:LDF for London dispersion, D-D for dipole-dipole, and HB for hydrogen bonding
(a) ethanol, CH3CH2OH LDF D-D HB
(b) ethanal, CH3CHO LDF D-D HB
(c) ethanoic acid, CH3COOH LDF D-D HB
(d) ethane, CH3CH3 LDF D-D HB
3. (2 pts) What forces account for the fact that many salts, such as KBr or calcium nitrate dissolve in water?4. Suppose a solution was prepared by dissolving 27.0 g potassium hydroxide (MM = 56.1 g/mol), in 100.0 g water. Use this table to organize your calculations.
MM mn
KOH 56.1 g mol-1
H2O 18.0 g mol-1
4a. (4 pts) What is the mole fraction of KOH?
Answer: ______
4b. (4 pts) What is the mass percent of KOH?
Answer with units: ______
5. HCl(aq) is 12.4 molar and has a density of 1.19 g/cm3.
MM m n V
HCl 36.5 g mol-1
H2O 18.0 g mol-1
Solution
5a. (4 pts) What is the molality of the HCl in this solution?
Answer with units: ______
5b. (4 pts) What is the mole fraction of HCl?
Answer: ______
6 (5 pts) True or False
T F Heating CO2(aq) will result in formation of bubbles.
T F Heating a saturated solution of sugar will cause more to dissolve
T F Increasing the pressure of CO2 above a solution of CO2(aq) will result in more CO2 dissolving.
T F Adding more sugar to a saturated solution will cause more sugar to dissolve.
T F Entropy change is positive when ionic substances dissolve
7. (5 pts) At 25 oC, pure water has a vapor pressure of 23.8 mmHg. Propylene glycol (from Question 1) is essentially non-volatile. What isthe vapor pressure of a solution that contains12 mol propylene glycol and 93 mol water?
Answer with units: ______
8. (5 pts) What is the boiling point of 5.3 molal solution of NaBr? Given: Water normally boils at 100 oC; Kb = 0.52 deg/molal
Answer with units: ______
9. (5 pts) What is the molar mass of a substance, known to be LiBr, NaBr, KBr or RbBr, given that 10.0 g of the saltwhen dissolved in 50.0 g water lowers the freezing point of water by 4.5 degrees?Kf = 1.86 deg/molal
Answer with units: ______
10. (4 pts) What is the osmotic pressure of a 0.017 M CaCl2 solution at 300 K? R = 0.0821 L atm mol-1K-1
Answer with units: ______
11a. (5 pts) We studied this reaction in classand determined it was first order in N2O5(g). Using the data provided, determine thevalue of the rate constant.
2 N2O5(g) 4 NO2(g) + O2(g)
Time (s) / [N2O5] (mol/L)0 / 0.0200
100 / 0.0169
200 / 0.0142
300 / 0.0120
/ Let me know if you cannot get this value as you will need it for Questions 11b – 11e. I will give you an alternative value but you will get no credit for this first question, 11a
11a.
Answer with units: ______
11b. (5 pts) What is [N2O5] after 500 s?
Answer with units: ______
11c. (5 pts) What is the half-life of the reaction?
Answer with units: ______
11d. (5 pts) How long until [N2O5] = 0.0080 M?
Answer with units: ______
11e. (5 pts) What is the rate of the reaction if[N2O5] = 0.050M?
11e.
Answer with units: ______
11f. (3 pts) How does the rate NO2 formation compare to the rate of N2O5 consumption? Say something like “The same” or “Half as large”
12. (6 pts). Suppose the reaction, A B gives a straight line when [A]t is plotted against time.
12a. What is the order? Circle Zero or Firstor Second
12b.How would the rate change if [A] increased by factor of 5? Circle No change or 5 X fasteror 25 X faster
12c. How does the rate law compare to the rate constant? They are the same or rate = k x timeor rate = k/time
13. A reaction is second order in butadiene, C4H6, with a rate constant of 0.0040 M-1s-1 and the initial concentration is 0.020 M.
13a. (5 pts) What is the molarity after 1.00 hr?Note time units!
Answer with units: ______
13b. (5 pts) What is the time in hours when the concentration reaches a value of 0.0020 M?
Answer with units: ______
13. (6 pts) Given A is red and B is blue, and the relative rates of the reaction A + B products is 1 : 2 : 2 : 4 for vessels A-D below, answer the following questions.
13a. What is the order of the reaction in A and B?Circle:
It is 0 or 1 or 2order in A and 0 or 1 or 2order in B
13b. What is overall reaction order? Circle:0 1 2 3 4
13c. Write the rate law (rate expression).
Total score (out of 100): ______
A+ 95% A 90% B+ 85% B 80% C+ 75% C 70% D 60%
Zero Order / First Order / Second OrderRate Expression / rate = k / rate = k[A] / rate = k[A]2
Test for order: Makes a straight-line Plot / [A]t vs t / ln[A]t vs t / 1/[A]t vs t
Time-Conc. Expression / [A]t = -kt + [A]o / ln([A]o /[A]t) = kt / 1/[A]t = kt + 1/[A]o
Half-life / t1/2 = [A]o /2k / t1/2 = 0.693/k / t1/2 = 1/k[A]o
Answers:
1a. Add two pairs of electrons to each oxygen atom.
1b. Yes
1c. Its an alcohol.
2.
(a) ethanol, CH3CH2OH LDF D-D HB
(b) ethanal, CH3CHO LDF D-D HB
(c) ethanoic acid, CH3COOH LDF D-D HB
(d) ethane, CH3CH3 LDF D-D HB
3. ion-dipole
4. MM mn
KOH 56.1 g mol-127 g 0.481 mol
H2O 18.0 g mol-1100 g 5.56 mol
4a. 0.0797
4b. 21.3%
5. MM m n V
HCl 36.5 g mol-1453 g 12.4 mol
H2O 18.0 g mol-1737 g 41.0 mol
Solution1190g1000 mL
5a. 16.8 molal
5b. 0.234
6 T T T F T
7. 21.08 mmHg
8. 105.5 oC
9. 165 g/mol
10. 1.26 atm
11a. 0.00170 s-1
11b. 0.00854 M
11c. 407 s
11d. 538 s
11e. 8.51 x 10-5 mol/(L s)
11f. twice as large
12. Zero, No change, They are the same
13a. 1.55 x 10-2 M
13b. 31.3 hr
13. (6 pts) Given A is red and B is blue, and the relative rates of the reaction A + B products is 1 : 2 : 2 : 4 for vessels A-D below, answer the following questions.
13a and b. first order in A and fist order in B and 2nd order overall
13c. rate = k[A]1[B]1