Review for Final Examination Copy Right by C. Chieh, UoWaterloo

Review for Final Examination

Skills to develop

To see how well have you prepared

Review for Final Examination

The CHEM 120 and CHEM 121 FINAL EXAMINATION is on 2-5 pm, Dec. 8, 1997?
The exam is written in the PAC gym areas, 1, 2, 3, 4, 5, 6, 7, 8, 11 (Main floor - large and small gyms).
Check the schedule to make sure. This file is out of date, and you should make sure yourself.

The CHEM120/121 final examination usually consists of two parts.

Part A. Written Questions: Usually you can choose 5 of 6

Part B. Multiple choice questions,

The examination covers the entire course, Chapters 3 to 11 including Survey 1. more or less evenly, but again, it depends on the prof's mood!

The DIALOGUE questions are some questions from old examinations. Note that these question are old, and they may not reflect the content of this term.

If too many of your answers are incorrect, you should stop practice, study hard, and then come back to PRACTICE again.

Press key to practice for yourself, NOT for anyone else. This is neither a quiz, nor exam. Written questions for practice are in another module.

Example Multiple Choice Questions

A mixture of 2.00 g of Pb and 2.00 g of I₂ was heated to attempt to make some PbI₂. How many grams of PbI₂ will be formed if the yield is 90%?
a. 3.63g
b. 2.22g
c. 2.00g
d. 4.00g
e. 3.27g

If your answer is...I'm lost!
Consider...
Concepts: limiting reactant, and stoichiometry.
If your answer is...e
Excellent...
Good!
These two solutions are mixed:
35.00mL of 0.284 M KCl
45.00mL of 0.196 M AlCl₃
Assuming that the volumes are additive, what is the concentration of Cl^- in the resulting solution?
a. 0.124M b. 0.235M c. 0.382M d. 0.436M e. 0.455M

If your answer is...I'm lost!
Consider...
35*0.284 + 45*3*0.196 / (35+45) = ? Concepts: concentration of solutions.
If your answer is...e
Excellent...
Good!
What weight of AlCl₃ is required to prepare exactly 100 mL of a solution which is 0.200 M with respect to the chloride ion?
a. 0.384g b. 1.78g c. 2.67g d. 8.00g e. 0.889g

If your answer is...I'm lost!
Consider...
Concepts: stoichiometry and concentration.
If your answer is...e
Excellent...
Good!
A stock solution of phosphoric acid labelled 24.0% H₃PO₄ by weight, has a density of 1.14 g/mL. What is the molar concentration of H₃PO₄ in this solution? [Molecular weights: H:1.00794; P:30.97; O:15.9994]
a. 2.79M b. 2.45M c. 1.14M d. 6.48M e. 11.6M

If your answer is...I'm lost!
Consider...
Practice unit conversion in concentration.
If your answer is...a
Excellent...
Good!
A sample of powdered iron, Fe weighing 1.231g is heated in a stream of chlorine gas and reacts completely, giving a sample of a compound of the two elements weighing 3.59g. The simplest formula of this compound is:
a. Fe₃Cl b. FeCl₃ c. Fe₂Cl d. FeCl₂ e. FeCl

If your answer is...I'm lost!
Consider...
Chemically, FeCl₂ and FeCl₃ exist. But here, you better calculate.
If your answer is...b
Excellent...
Good!
How many molecules are contained in 1.85 L of a gas at 0.839 atm pressure and 25 C° ?
a. 4.55 * 10²³ molecules b. 3.82 * 10²³ molecules c. 4.97 * 10²³ molecules d. 9.48 * 10²³ molecules e. 3.76 * 10²³ molecules

If your answer is...I'm lost!
Consider...
Calculate n in PV = nRT, and then n * Avogadro's number N.
If your answer is...b
Excellent...
Good!
The reaction in basic solution,
S^2- + Cr₂O₇^2- -----> S + Cr(OH)₄^-
when balanced and written with the smallest integer stoichiometric coefficients, the coefficient of H₂O is
a. 3 b. 5 c. 7 d. 9 e. 12

If your answer is...I'm lost!
Consider...
Practice balance redox reactions.
If your answer is...c
Excellent...
Good!

The first law of thermodynamics states that the internal energy of a system always increases if:
a. work is done by the system and heat flows out of the system b. work is done on the system and heat flows out of the system c. work is done on the system and heat flows into the system d. work is done by the system and heat flows into the system e. work is done by the system and there is no heat flows

If your answer is...I'm lost!
Consider...
Recall definition of internal energy.

If your answer is...c
Excellent...
Good!

Calculate the density of neon gas at 20.0 C° and 1.00 atm pressure.
a. 22.4 g/L b. 0.839 g/L c. 12.3 g/L d. 20.1 g/L e. 1.68 g/L

If your answer is...I'm lost!
Consider...
Derive the formula: PM = dRT. Then d = ? Mol. wt. of Ne = 20.18
If your answer is...b
Excellent...
Good!

Use the Heat of formation (Hf) below to calculate the enthalpy change for the reaction,
ZnO (s) + H₂O (l) ---> Zn(OH)₂ (s).
Zn(s) + 1/2 O₂(g) --> ZnO(s) Hf = -348.1 kJ/mol Zn(s) + H₂(g) + O₂(g) --> Zn(OH)₂(s) Hf = -642.2 kJ/mol H₂(g) + 1/2 O₂(g) --> H₂O(l) Hf = -285.8 kJ/mol
a. +8.3 kJ/mol b. -704.6 kJ/mol c. +1276 kJ/mol d. -8.3 kJ/mol e. -1276 kJ/mol

If your answer is...I'm lost!
Consider...
dH = Sum of Hf of products - Sum of Hf of reactants

If your answer is...d
Excellent...
Good!

Sulfur dioxide reacts with oxygen gas to produce sulfur trioxide. What volume of O₂ gas will react with 15.0L of SO₂ if both gases are at 101.3 kPa and 100C°?
a. 5.00 L b. 3.75 L c. 7.50 L d. 30.0 L e. 15.0 L

If your answer is...I'm lost!
Consider...
SO₂ + O₂ = SO₃ balance it to find out.
If your answer is...c
Excellent...
Good!
A bomb carimeter has a heat capacity of 2.47 kJ/K. The combustion in this bomb of a 0.105 g sample of ethylene, C₂H₄(g), causes a temperature rises of 2.14K. What is dE, in kilojoules per mole of ethylene, for this combustion reaction?
a. -5.29 kJ/mol b. -50.3 kJ/mol c. -572 kJ/mol d. -660 kJ/mol e. -1.41 * 10 ^ 3 kJ/mol

If your answer is...I'm lost!
Consider...
Energy is released. Note the units.
If your answer is...e
Excellent...
Good!

For the electron configuration shown below, which of the principles used to determine the ground state atomic electronic configuration has NOT been obeyed.
Note: TREAT " / as spin up and \ as spin down " /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ / / -- -- -- -- -- -- -- -- -- -- -- -- -- 1s 2s 2p 3s 3p 4s 4p a. Pauli exclusion principle b. Aufbau principle c. Hund's rule d. Heisenberg's Uncertainty Principle e. None, the configuration shown is correct.

If your answer is...I'm lost!
Consider...
3d orbitals should be filled before 4p according to the Aufbau principle.

If your answer is...b
Excellent...
Good!

Given the following reactions (dH1 represents the standard enthalpy change),
B --> A dH2 B --> C dH3 For the transformation A --> C the enthalpy change, dH1, is a. dH1 = dH2 + dH3 b. dH1 = dH2 - dH3 c. dH1 = dH3 - dH2 d. dH1 = 2dH2 - dH3 e. dH1 = dH3 + dH2

If your answer is...I'm lost!
Consider...
Practice calculation using Hess law.

If your answer is...c
Excellent...
Good!

Which hydrogen halide is a weak acid?
a. HBr b. HF c. HI d. HCl e. All are strong

If your answer is...I'm lost!
Consider...
HF is a weak acid due to very strong bond H-F.
If your answer is...b
Excellent...
Good!
Which metal forms a superoxide when oxidized in the presence of abundant oxygen?
a. Na b. Rb c. Be d. Sr e. Li

If your answer is...I'm lost!
Consider...
A problem from Survey 1.
If your answer is...b
Excellent...
Good!

Which of the following statements are CORRECT?
1. When light strikes a metal in a vacuum, photoelectrons are emitted, provided the lambda of the light striking the metal is longer than the (lambda 0) required for photoemission. 2. According to the de Broglie theory the wavelength associated with a proton travelling at 1.0*10⁶ m/s would be longer than that of an electron travelling at the same speed. 3. One of the valence electrons in a ground state phosphorous atom could be described using the four quantum numbers, as 3, 1, -1, +1/2. 4. For any n value equal to or greater than 4, there are seven available f orbitals. 5. Atoms of all of the elements in Group VI (the oxygen group) of the periodic table, in their ground state, are paramagnetic. a. 1, 3, 4, 5 b. 2, 3, 4, 5 c. 3, 4, 5 d. 1, 4, 5 e. 1, 2, 3

If your answer is...I'm lost!
Consider...
3, 4, 5 are correct statements.

If your answer is...c
Excellent...
Good!

Choose the one INCORRECT statement from the following.
a. The lattice energy of MgF₂(s) is larger than the lattice energy of NaF(s) b. Based on electronegativity differences you would expect lithium fluoride to be less ionic than cesium fluoride. c. The formal charge on the central oxygen in the ozone molecule, O₃ is -1. d. The bond length of the ClF molecule is shorter than the bond length in Cl₂. e. The boron trifluoride molecule, BF₃, does not have a dipole moment.

If your answer is...I'm lost!
Consider...
Develop critical thinking ability.

If your answer is...c
Excellent...
Good!

The dipole moment of gaseous LiH is 1.96*10^-29 Cm. The interionic distance is 159.6pm. What is the % ionic character of the LiH bond? [Note: The fraction of a unit of charge centred on a nucleus in a polar bond is a measure of the ionic character of a bond.]
a. 13% b. 77% c. 58% d. 43% e. 31%

If your answer is...I'm lost!
Consider...
Calculate percent of charge on the nucleus.
If your answer is...b
Excellent...
Good!

Choose the one INCORRECT statement.
a.  Oxygen is the second most electronegative element.
b.  Most metal oxides are basic
c.  NO₂ is a brown paramagnetic gas which forms the colorless diamagnetic
    dimmer, N₂O₄(g).
d.  For a given halogen, the oxo acid strength decreases with increasing
    oxidation number of the halogen atom.
e.  Nitrogen can have oxidation states of -3, -2, -1, 0, +1, +2, +3, +4, +5.

If your answer is...I'm lost!
Consider...
This problem comes from Survey 2.

If your answer is...d
Excellent...
Good!

What is the correct electronic configuration for the ion Zn²⁺
     a. [Ar] 4s² 3d¹⁰ 4p⁰
     b. [Ar] 4s² 3d⁸ 4p⁰
     c. [Ar] 4s² 3d¹⁰ 4p²
     d. [Ar] 4s⁰ 3d¹⁰ 4p⁰
     e. [Kr] 4s² 3d¹⁰ 4p⁰

If your answer is...I'm lost!
Consider...
The two s electron are removed in this ion. You may also need a periodic table to answer this problem.

If your answer is...d
Excellent...
Good!

Most sodium is prepared on an industrial scale by:
a. the reduction of sodium oxide and hydroxide by hydrogen.
b. the reaction of sodium hydroxide with aluminum.
c. the electrolysis of fused molten sodium chloride.
d. neutralization of sodium hydroxide with concentrated nitric acid.
e. electrolysis of brine (aqueous sodium hydroxide).

If your answer is...I'm lost!
Consider...
Sodium is too reactive for any chemical reduction.

If your answer is...c
Excellent...
Good!

In the ClF₃ molecule what are the hybrid orbitals on the Cl atom?
a. sp³ b. sp² c. sp³d d. sp³d² e. (sp²)(sp)

If your answer is...I'm lost!
Consider...
Check the shape of ClF₃, and count the number of atomic orbitals used.
If your answer is...c
Excellent...
Good!

Which of the following statements about the molecular orbitals of diatomic molecules is TRUE? (The two nuclei lie along the x axis, as in your text)
a. an antibonding molecular orbital always has lower energy than the bonding molecular orbital formed from the same atomic orbitals. b. the sigma(3s) molecular orbital has higher energy than the sigma*(3s) molecular orbital. c. the pi(2py) molecular orbital has the same energy as the pi(2pz) molecular orbital. d. the pi(2py) molecular orbital has the same energy as the pi(3pz) molecular orbital. e. all bonding orbitals are filled before any antibonding orbitals are filled.

If your answer is...I'm lost!
Consider...
This requires some thinking. Study chemical bonding.

If your answer is...c
Excellent...
Good!

Which is the molecular orbital electron configuration of the diatomic molecule, BN? (The two nuclei lie on the z axis, as in your text.)
a. (sig1s)² (sig*1s)² (sig2s)² (sig2px)² (pi2py)² (pi2pz)² b. (sig1s)² (sig2s)² (sig2pz)² (pi2py)¹ (pi2px)¹ c. (sig1s)² (sig*1s)² (sig2s)² (sig*2s)² (sig2pz)² (pi2py)¹ (pi2px)¹ d. (sig1s)² (sig*1s)² (sig2s)² (sig*2s)² (sig2pz)² (pi*2px)² e. (sig1s)² (sig*1s)² (sig2s)² (sig*2s)² (pi2py)² (pi2px)²

If your answer is...I'm lost!
Consider...
Would have been simpler if we use symbols. Review Molecular Orbital approach to chemical bonding.

If your answer is...e
Excellent...
Good!

When the following equation for reaction in aqueous acidic solution is balanced and written with the smallest integer stoichiometric coefficients, the coefficient for H(+) is:
Cr₂O₇^2-(aq) + CH³OH (aq) ---> Cr³⁺ + CH₂O (aq) a. 8 on the left side of the equation b. 7 on the left side of the equation c. 14 on the left side of the equation d. 6 on the right side of the equation e. 4 on the right side of the equation

If your answer is...I'm lost!
Consider...
Balance Redox Equation.
If your answer is...a
Excellent...
Good!
Which of the following is not a peroxide?
a CH₃-CH₂-O-O-H b H₂O₂ c Na₂O₂ d BaO₂ e H₂SO₄

If your answer is...I'm lost!
Consider...
Sulfuric acid is not a peroxide.
If your answer is...e
Excellent...
H₂SO₄ is the formula for sulfuric acid

Which orbital do the following figures represent?
                                           |y
    Psi^2 |                                X 
          |                               XXX 
          |                           XX   V   XX
          |     **               --      --> x
          |   *     *                 XX   A   XX
          | *          *                  XXX
          |_______________*__              X 

a  1s     b  2s   c   2p   d  3d  e  3p

If your answer is...I'm lost!
Consider...
The two figures are associated with a d orbital.

If your answer is...d
Excellent...
These are crude figures

A mixture of BaCl₂ and BaI₂ weighting 1.392g is dissolved in water and treated with excess Na₂SO₄, causing all of the barium to precipitate as BaSO₄. The precipitate, when dried, weighs 1.031 g. What is the percent, by mass, of BaCl₂ in the mixture? Data: a.w. of Ba 137.3; Na 22.99; Cl 35.453; I 126.9; S 32.06; O 15.9994
If your answer is...I'm lost!
Consider...
The answer is Hummmmm...
Try using the concept of "mole": n BaCl₂ + n BaI₂ = n BaSO₄
If your answer is...27.5%
Excellent...
Good!

) cchieh@uwaterloo.ca