SI Chem 167 - Exam 3 Material Review
1. Which of the following contains one pi bond
a) C2H6
b) Pz-Pz Bond
c) N2
d) O2
2. In a chemical reaction, typically energy is _______ when breaking bonds, and _________
by creating bonds.
a) Released / released
b) Released / absorbed
c) Absorbed / Released
d) Absorbed / Absorbed
3. Which molecule has the most resonance structures?
a) CO3 2b) SO 4 2c) NO3d) CNS4. For the molecule XeF4, what is the correct geometry and angle(s)?
a) Square Planar: 90
b) Tetrahedral: 90
c) Tetrahedral: 120
d) Seesaw: 90 and 120
5. In a T-Shaped molecules, the angles are
a) 90 and 180
b) Less than 90 and 180
c) Less than 90 and less than 180
d) 90 and less than 180
6. Which molecule is most polar?
a) CH4
b) CH3F
c) CH3Br
d) CH3I
e) CH3Cl
7. What is the hybridization of the molecule: HCN
a) Sp
b) Sp2
c) Sp3
d) Sp and Sp3
8. A metal has the density of 10.7 g /cm3, molar mass of 127.4 g/mol. The metal is in a
simple cubic unit cell formation. What is the diameter of a metal atom in cm?
a) 2.7* 10-7
b) 2.8 * 10 -8
c) 2.8 * 10 -7
d) 2.7 * 10 -8
i. 1 atom ( 1 mol / 6.022*10^23)(127.4 g / 1 mol) =mass
ii. V= m/d
iii. Diameter = (v)^1/3
9. For Phosphorous, ____ is an example of p doping and ____ is an example of n doping.
a) Sulfur / Silicon
b) Carbon / Selenium
c) Silicon / Sulfur
d) Oxygen / Boron
10. Which will have the highest vapor pressure?
a) CH3CH3
b) CH3CH2Br
c) CH3CH2 CH2 CH2F
d) CH3CH2 CH2 CH2OH
11. What is the vapor pressure at 273.2 K?
a) .006 Torr
b) 218 Atm
c) 1 Torr
d) .006 Atm
12. Which of the substances can form hydrogen bonds?
a) CH4
b) CH3OH
c) CH3F
d) NF3
13. In a reaction, delta H turns out to be negative. What does this mean?
a) Disorder increased
b) Disorder decreased
c) Work is done by the system
d) Work is done on the system
14. If delta H is negative and delta S is also negative, the reaction is spontaneous at
a) Never
b) At high temperatures
c) Low temperatures
d) All temperatures
15. Calculate delta H: C2H6(g) + (7/2) O2(g)  2 CO2(g) + 3 H2O(g)
Substance
Delta H Molecule
C2H6
-90
CO2
-400
H2 O
-150
a) -1160
i. =[2(-400) + 3 (-150)] - [ 1(-90) ]
b) -1340
c) -1530
d) -1100
16. 1.00 mole of a O2 combusts completely in a bomb calorimeter. The temperature of the
calorimeter changes from 30 C to 83 C. If the heat capacity of the calorimeter is 0.726
kJ/K, what is Q for the combustion of 1 mol of the O2?
a) 615.6 kJ
i. Q=mct
ii. Q= 16g (.726)(83-30)
b) 712.8 kJ
c) -615.6 kJ
d) -712.8 kJ
17. 28.0 g of ice is heated from –16.00C to –2.00C. What is the heat flow, q ice? The
specific heat of ice is 2.10 J/gC H of melting (fusion) for ice is +6.01 kJ/mol
a) 745 J
b) 856J
c) 754J
d) 823 J
i. Q=mct
ii. = 28 (2.10)(-2 - -16)
18. Spontaneous process
a) Never occur in nature
b) Always have a negative delta S
c) Always have a positive Delta H
d) Are quick
e) Do not need continuous intervention
19. Which has the highest entropy?
a) Gas at 475 K
b) Water at 273 K
c) Solid at 264 K
20. A reaction has a delta H of -293 and a delta S of -23. At what temperature does the
reaction become spontaneous?
a) Never spontaneous
b) 12 K
i. G= H –ST
ii. G=0
iii. 0= -293-( -23(T))
c) 298 K
d) 56K