Download Chemistry 123: Physical and Organic Chemistry

Chemistry 123: Physical and Organic Chemistry
Midterm 2
March 13, 2009
Name: ______________________
Student ID#: ________________
/50
Total Marks
1) The optical rotation of plane-polarized light of the reactant molecule
presented below is +121.1°. Show the reaction products and indicate the net
optical rotation of the products in the SN1 reaction presented below?
2) Indicate the relationship between the two molecules presented below and
indicate which is more stable and why.
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Chemistry 123: Physical and Organic Chemistry
Midterm 2
March 13, 2009
3) If the ratio of Carbon-14 to Carbon-12 in a living tree is 1.3 x 10-12, what will
this ratio be in 2000 years if the half life (t) of Carbon 14 is 5730 years? What
is the rate (k) of the carbon-14 decay?
.
4) If a “Van Hoff plot” is generated for a reaction and a linear regression of this
plot indicates a “best fit” line of Y= 9273.5X – 14.6 Calculate the values for ΔH
and ΔS. If the temperature if set to 30°C, would the reaction be spontaneous?
Support your assertion by calculating the value for ΔG.
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Chemistry 123: Physical and Organic Chemistry
Midterm 2
March 13, 2009
5) Consider a beaker containing 18 mL of water initially at 20°C that is cooled to
to -10°C. Describe each step of the process and calculate the amount of energy
that would need to flow in or out of the system. At each step indicate if the
entropy is increasing or decreasing and under what conditions the reaction would
be spontaneous.
6) Concisely state the 3 laws of Thermodynamics preferably using formula’s.
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Chemistry 123: Physical and Organic Chemistry
Midterm 2
March 13, 2009
7) If the ΔG° for the reaction below is -33.3 kJ/mol and the initial partial pressures
of each of the gasses is given below the equation, calculate the ΔG for the
reaction at 50°C. Is it spontaneous? What is the equilibrium constant for this
reaction?
N2(g) +
3 H2(g)
1.0 atm
3.0 atm
↔
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2NH3(g)
0.5 atm
8) ΔfH° of NH3 is -80.29 kJ/mol, determine ΔS° for the reaction presented in
question 7.
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Chemistry 123: Physical and Organic Chemistry
Midterm 2
March 13, 2009
/11 (1 point each)
Multiple Choice (circle best answer)
8) Which best describes this chemical structure?
A) Primary amine
C) Secondary amine
B) tertiary amine
D) none of these
9) For the chemical structure presented in question 8, which best describes the
carbon connected to the NH2 group.
A) Primary carbon
B) tertiary carbon
C) Secondary carbon
D) none of these
.
10) For the chemical structure presented in question 8, How many secondary
hydrogen atoms are there?
A) 9
B) 0
C) 2
D) 4
11) Which of the following correctly names the chemical structure presented in
question 8?
A) 2-methylbutan-2-amine
C) Tert-butamine
B) Dimethyl-propanamine
D) 2,methyl-2,amine butane
12) What of the following is most reactive in an SN1 reaction?
A) Primary alkyl halide
B) tertiary alkyl halide
C) Secondary alkyl halide
D) not enough information to determine
.
13) For graphite which would be numerically larger?
(A) ΔfG°
(B) ΔfH°
(C) ΔS°
14) Which of the following would have the greater ΔS?
(A) C(s)
(B) C(g)
(C) CO(g)
(D) CO2(g)
15) If a reaction has a half-life of one day and it is initiated on Monday, how much
remains on Friday?
(A) ~20%
(B) ~5%
(C) ~3%
(D) ~12%
16) For the reaction, N2(g) + 3 H2(g) ↔ 2NH3(g) , the rate would be;
A) First order
B) Second order with regard to [NH3]
C) Third order
D) not enough information to determine
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Chemistry 123: Physical and Organic Chemistry
Midterm 2
March 13, 2009
17) CO2 is a greenhouse gas because….
(A) It absorbs infrared radiation
(B) It has a high entropy
(C) It makes plants grow better in a greenhouse
(D) It has a high enthalpy of formation
18) Carbon dating is possible due to;
(A) open minded rate laws
(B) Irradiation of N2(g) by cosmic radiation
(C) Naturally occurring Carbon isotopes (D) radioactivity from nuclear bombs
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