University Transfer Courses and Noncredit English Courses

Chemistry 121, Final exam

University Transfer Courses and Noncredit English courses

Grade % Points Rating

A+ 90-100 4.3 Excellent
A 85-89 4.0
A- 80-84 3.7 Very Good
B+ 76-79 3.3
B 72-75 3.0
B- 68-71 2.7 Good
C+ 64-67 2.3
C 60-63 2.0 Satisfactory
C- 55-59 1.7
D 50-54 1.0 Marginal Pass
F 0-49 0.0 Fail

University Transfer Courses and Noncredit English courses

Grade % Points Rating

A+ 90-100 4.3 Excellent
A 85-89 4.0
A- 80-84 3.7 Very Good
B+ 76-79 3.3
B 72-75 3.0
B- 68-71 2.7 Good
C+ 64-67 2.3
C 60-63 2.0 Satisfactory
C- 55-59 1.7
D 50-54 1.0 Marginal Pass
F 0-49 0.0 Fail

Foundation Courses

For foundation courses the College uses the grading system recommended by the BC Ministry of Education.

Grade % Points Rating

A 86-100 4.0 Excellent
B 73-85 3.0 Very Good
C+ 67-72 2.5 Good
C 60-66 2.0 Satisfactory
C- 50-59 1.0 Pass
F below 50 0.0 Fail
I below 50 0.0 In Progress/Incomplete

It should be noted that a grade of C- (secondary system) or D (university system) indicates a marginal pass and is not a sufficient grade for the course to fulfill a prerequisite requirement. See page 26 for other terms that may appear on a student’s permanent record.

Chemistry 121

FINAL EXAM

Version A

Section:

Name:

Student I.D.:

This exam contains pages numbered 1 through 11 and a detachable periodic table/data sheet.

Instructions:

Answer the questions in the space provided.

You may use the backs of pages for calculations if necessary.

You must clearly show your method to receive full credit for the calculation problems.

Make sensible use of significant figures.

Write out any equations you use and show all your work.

Include units with the final answer whenever appropriate

1) Magnesium sulfate forms a hydrate, MgSO4. nH2O, which is 51.2 % water by mass. Calculate the number of water molecules in the molecular formula (find the value of n). (3marks)

2) If 4.0 ×1024 molecules of N2, 4.0 g of H2, 6.0 moles of O2 are placed in an 8.2 L container at 127°C, what would be (i) the mole fraction of each gas, (ii) the total pressure in the flask, and (iii) the partial pressure of each gas? (6 marks)

3) Determine the relative rates of diffusion of hydrogen gas and oxygen gas at 25◦C? (3 marks)

4) Which of the following would be considered a solution? (2 marks)

A) Water B) Mercury C) Air D) Supercritical CO2 E) None of these

5) Sketch all of the orbitals with a principal quantum number equal to 2. (3 marks)

6) For the following molecules give the: (10 marks)

a) Lewis structure

b) electron geometry (draw it)

c) molecular geometry

c) hybridization on the central atom

d) and indicate whether the molecule is polar or not (consider electronegativity values, lone pairs of electrons and the VSEPR shape). Take the Pauling electronegativity value for Xe to be 2.6.

AsCl5 NO3- ICl3 XeCl4

7) The cyanate ion, NCO−, forms many stable salts with various metal ions, whereas, the isomeric fulminate ion, CNO− forms extremely unstable and explosive salts.

a) Draw the Lewis structures for these ions. If these ions show resonance, draw all the other structures that contribute to the resonance hybrid, include formal charges and lone pairs.

b) Clearly indicate the order of contribution (which contributes the most and which contributes the least) for each of your structures to the resonance hybrid and give your reasons.

c) Comment on any differences that might relate to differences in stability.

(8 marks)

8) Of the following compounds of sulfur, which, if any, do not possess a permanent dipole. Take the Pauling electronegativity value for a lone pair = 3.7. (4 marks).

SF2 SF3+ SF4 SF5+

9) Draw a structure that shows the valence bond orbital overlap for the following: (6 marks).

a)  methanal, HCOH

b)  methanol, CH3OH

10) Draw the molecular orbital energy diagram for C2, N2 and determine: ( 6 marks).

a) Which species would have:

(i)  the weakest bond?

(ii)  the shortest bond?

b) List the following from left to right in order of increasing paramagnetism:

CN- B2 C2+

11)

a)  Which chloride should have the greatest covalent character? ( 2 marks)

A) NaCl B) BeCl2 C) KCl D) BaCl2 E) CaCl2

b)  Which of the following exhibits ionic bonding? (2 marks)

A) C2H6 B) Na2S C) H2CO D) SiCl4 E) SF4

12) Draw the Lewis dot structure of HC(O)OH and pick the INCORRECT statement from the following. (2 marks)

A) The oxygen not also bonded to hydrogen has a double bond to carbon.

B) The carbon has a lone pair.

C) Both oxygens have two lone pairs.

D) The O-H bond is a single bond.

E) The C-H bond is a single bond.

13) Which of the following has a molecular structure that can be represented without use of an "expanded octet"? (2 marks)

A) Fe(CN)63- B) C2Cl6 C) SF6 D) PF5 E) PtCl5-

14) Choose the groups of molecules below in which all the molecules have a net dipole moment. (2 marks)

A) SiHCl3, O2, H2O

B) HF, H2C=CH2, H2O

C) HF, CH3Cl, H2O

D) CCl4, HCl, NH3

E) HF, H2O, N2

15) A hydrogen electron makes a transition directly from n = 5 to n = 2. Is energy absorbed or transmitted during the transition? ( 2 marks)

16) Ionization energy (IE) increases from left to right on the periodic table and is a measure of the energy required to abstract an electron. Yet the first IE for phosphorus is larger (10.5 volts) than the first IE of sulfur (10.4 volts). Explain this exception. (3 marks)

17) Arrange the following in order of increasing attraction to a magnetic field. Show your work.

(5 marks).

Mg

B

Ge

As

Cr

18) Which of the following chlorofluorohydrocarbons is chiral; show the structures and the chiral center.

(2 marks)

a) CF3CH2CCl3

b) CF2HCHFCCl3

c) CClFHCHHCCl2F

19) How many primary, secondary, tertiary and quaternary carbon atoms are there in the structure of 2,4,6-trimetylheptane? Draw the structure. (3 marks)

20) In each of the following groups of substances, pick the one that has the given property. For each species you must describe the appropriate attractive force and estimate its strength.

(6 marks).

a)  Highest boiling point: CO2, NH3, SnO2, C4H10

b)  Largest vapor pressure at 25°C: CH3OCH3, CH3CHO, CH3CH2CH3, CH3CN

c) Lowest boiling point: CBr4, CCl4, CI4, CF4

21) Arrange the following compounds in order of increasing boiling point:

Provide your reason. (2 marks).

I) 1-propanol, CH3CH2CH2OH;

II) 1,2-propanediol, CH3CH(OH)CH2OH;

III) 1,2,3-propanetriol, (glycerol), HOCH2CH(OH)CH2OH.

22) This question refers to the phase diagram of carbon dioxide (see below).

a)  Identify the triple point and critical temperature on this diagram.

b)  What phase change occurs when frozen carbon dioxide is warmed under 1 atm pressure?

c)  What is the minimum pressure needed for liquid carbon dioxide to be stable?

d)  The atmosphere on Mars has a surface pressure of about 0.007 atm and a temperature ranging from −143ºC to 27ºC. It consists of mostly carbon dioxide gas (95%), but some water vapour is present. Can liquid carbon dioxide exist on the Martian surface?

Explain why?