Chem 167 Exam 3 Review

  1. Given the electronegativities below, which covalent bond is most polar?

Element: HCNO

Electronegativity:2.12.53.03.5

  1. C-H
  2. N-H
  3. O-H
  4. O-C
  5. O-N
  1. Among the following molecules, only ______is polar.
  2. BeCl2
  3. CBr4
  4. NF3
  5. AlCl3
  6. Cl2
  1. Draw lewis structures for the following molecules. Give the shape of the molecule, hybridization of the central atom, and the bond angle(s).
  2. CH2F2
  1. OF2
  1. PO33-
  1. BCl3
  1. BeF2
  1. PBr5
  1. The total number of σ bonds in the H-CΞC-CΞC-CΞC-CΞN molecule is
  2. 4
  3. 6
  4. 8
  5. 12
  6. 15
  1. In ethylene (H2C=CH2), the C=C double bond results from _____ overlap of _____ orbitals and ______overlap of ______orbitals on the C atoms.
  2. σ, sp, π, p
  3. σ, sp2, π, sp2
  4. σ, sp3, π, s
  5. σ, sp2, π, p
  6. π, sp2, σ, p
  1. Which drawing represents a π bonding molecular orbital for a homonuclear diatomic molecule?
  1. Which of the following molecular species is stabilized by resonance?
  2. CO2
  3. N3-
  4. BH3
  5. O22-
  6. HCN
  1. What is the coordination number for (a) simple cubic (b) body-centered cubic (c) face-centered cubic? Which is close packed?
  1. Nickel crystallizes in a face-centered cubic lattice. If the density of the metal is 8.908 g/cm3, what is the unit cell edge length in cm?
  1. Draw the electronic structures of a conductor, semi-conductor, and insulator.
  1. __ - type doping involves a dopant with more valence electrons than the substance. __ - type involves a dopant with fewer valence electrons.
  1. For the following molecules, describe which intermolecular forces are present and rank them in order of increasing strength.
  1. C4H10
  2. Br-I
  3. CH4
  4. F-Cl
  5. CH3NH2
  1. Which of the following statements about intermolecular forces and liquid properties is false?
  2. The hydrogen bonding force is the strongest intermolecular force.
  3. Stronger intermolecular forces cause a higher boiling point in the liquid state.
  4. Stronger intermolecular forces cause a higher vapor pressure in the liquid state.
  5. Water has a high surface tension because of its strong intermolecular forces.
  6. Gasoline is more volatile than water.
  1. A piece of copper metal of mass 6.22 kg is heated from 20.5 °C to 324.3 °C. Calculate the heat absorbed by the metal. Specific heat is 0.386J/g °C.
  1. If 3.4 kJ of heat flows out of the system while 4.8 kJ of work is done by the system on the surroundings, what is the internal energy?
  1. Given the following reactions,

2 S(s) + 3 O2 (g)  2 SO3(g)ΔH = -790 kJ

S(s) + O2(g)  SO2 (g)ΔH = -297 kJ

What is ΔH° for the reaction 2 SO2(g) + O2(g)  2 SO3(g)?

  1. Write the formation reaction for CaCO3.
  1. Silane, SiH4, burns according to the reaction, SiH4 + 2 O2 SiO2 + 2 H2O, with ΔH° = -1429 kJ. How much energy is released if 15.7 g of silane is burned?
  1. Find the ΔH°rxn for C2H6(g) + 7/2 O2(g)  2 CO2(g) + 3 H2O(g)

ΔH°f C2H6(g) = -84.7 kJ/mol

ΔH°f CO2(g) = -393.5 kJ/mol

ΔH°f H2O(g) = -241.8 kJ/mol

  1. How much heat must be removed to change 75.0 grams of water at 25.0 °C to ice at -35.0 °C?ΔH°fusionice = 333.55 J/g; specific heat of ice = 2.03 J/g °C
  1. Determine the final temperature when 10.0 g of aluminum at 130.0 °C mixes with 200.0 grams of water at 25.0 °C. The specific heat of aluminum is 0.901 J/g °C. (Coffee cup calorimeter problem.)
  1. A 0.500 g sample of naphthalene (C10H8) is burned in a bomb calorimeter containing 650 grams of water at an initial temperature of 20.00ºC. After the reaction, the final temperature of the water is 26.4ºC. The heat capacity of the calorimeter is 420 J/ºC. Using these data, calculate the heat of combustion of naphthalene in kJ/mol.
  1. Considering the definition ΔG=ΔH-TΔS, match the following possible combination of ΔH and ΔS(in terms of negative or positive signs).

ΔH ΔS

+ + _____

- - _____

- + _____

a) Always spontaneous at all temperatures b) only spontaneous at low temperatures

c) Only spontaneous at high temperatures.

22.Using the thermodynamic data, determine if the following reaction is spontaneous at only high or only low temperatures?(ΔS NO=210.7J/mol*K, N2=191.5 J/mol*K, O2=205.0 J/mol*K)

N2(g)+O2(g)+ 180.5 kJ 2NO(g)

23. Consider 10.0 g of water placed in a freezer at -15°C. What is the entropy change of the surrounding when the water freezes? For water ΔHfusion=338J/g.