CHEMISTRY 139
MIDTERM #2
NOVEMBER 23, 2011
1. What evidence is there that hydrogen has quantized energy levels.
2. A chlorinated hydrocarbon with a molar mass of 338.94 g/mole is composed of
31.899%C, 5.353%H, and 62.76%Cl. Find the empirical and molecular formulas.
3. Draw Lewis structures for the following.
a. C
b. N3c. CaC2
4. For carbonic acid H2CO3 give a Lewis structure, molecular shape, formal charges,
bond angles and the polarity. P = 8(n-q) + 2q -2(n-1)-v
5. Given the following thermochemical data:
2O3 → 3O2
ΔH = -427 kJ
NO + O3 → NO2 + O2
ΔfH = -199 kJ
Calculate ΔH, using Hess’s Law for the following reaction.
NO + O2 → NO2 (balance before proceeding)
6. Calculate the amount of energy required to heat 145 g of water from 22.3°C to 75.0°C,
using the specific heat of water as 4.184 j/g-°C.
7. For the reaction S + O2 → SO2 + ΔH= -296 kJ per mole of sulfur.
Calculate the quantity of heat released when 2.00 g of sulfur is burned in 1.50g oxygen.
8. Give the electronic configuration, the valence configuration, and the number of valence
electrons for Au. You may abbreviate if you like.
9. Which element has the same number of electrons is the 2p orbital as it has in the 3d
orbital?
10. What two thermodynamic forces are used to determine a spontaneous change?
11. How are the wavelength and energy related?
12. List three cations that are isoelectronic with neon.
13. Why do metals tend to form cations and nonmetals tend to form anions?
14. Which element has the highest ionization energy?
15. For each of the following bonds, draw a figure indicating the direction of the bond
dipole, including which end of the bond is positive and which is negative.
a. SiH
b. S-H
c. N-S
d. N-O
16. It takes 1.25 kj of energy to heat a certain sample of pure silver from 12.0°C to 15.2°C.
Calculate the mass of the sample of silver. The specific heat of silver is 0.24 j/g-°C
17. A 50.0 g sample of water at 99.8°C is poured into a 50.0 g sample of water at 25.0°C.
What will be the final temperature of the water?
18. Label the following as endothermic or exothermic
a. The combustion of gasoline in a car engine
b. Water condensing on a cold pipe
c. Co2(s) → CO2(g)
d. F2 (g) → 2F (g)