Latest Version: 6.0

Question: 1

Most names of binary compounds don't include any numbers (for example, "aluminum hydroxide," "barium oxide," etc.). So why is "iron(II) chloride" written with a number?

A. Iron has more than one possible isotope

B. It is a stylistic preference but doesn't need to be written this way

C. It is a remnant of an old nomenclature system but doesn't need to be written this way

D. Iron has more than one possible oxidation state

E. There are multiple types of the iron element

Answer: D

Explanation:

Some metals (iron, copper, gold, tin, chromium, mercury, and lead) can form two or even three oxidation states. Since iron can form a 2+ or 3+ ion, the name "iron chloride" could indicate either FeCl2 or FeCl3. We, therefore, include the oxidation state of iron for clarification.

Question: 2

In a crystalline solid, what is the coordination number?

A. The amount of energy required for a peripheral molecule to sublime

B. The average distance between two nuclei in the lattice

C. The number of atoms adjacent to any one atom in the crystal lattice

D. The number of atoms per unit cell in the crystal lattice

E. The amount of energy released by a new molecule getting added to the lattice

Answer: C

Explanation:

For example, a simple cubic structure has a coordination number of 6 while a hexagonal, closely-packed structure has a coordination number of 12.

Question: 3

You have 100 mL of 1M HCl and titrate it with an unknown potency of NaOH until the solution's pH is 7. When the solution is neutralized, you observe that you have added approximately 150 mL of NaOH. What is the molarity of your NaOH solution?

A. 0.67M

B. 0.33M

C. 1M

D. 2M

E. 1.5M

Explanation:

Answer: A

When an acid and base neutralize each other, you need the same molar equivalent of acid and base to reach the neutral pH 7:

MNaOH(150mL) = MHCl(100mL)

MNaOH = (1M * 100mL) / (150mL)

MNaOH = 0.67M

Question: 4

How does the atomic radius of a neutral atom compare to the radius of its cation? Its anion?

A. Neutral atom > cation; neutral atom < anion

B. Neutral atom > cation; neutral atom > anion

C. Neutral atom = cation; neutral atom < anion

D. Neutral atom = cation; neutral atom > anion

E. Neutral atom > cation; neutral atom = anion

Answer: A

Explanation:

If an atom loses an electron to become a cation, its radius shrinks because the atom has lost its outermost electron and has a newly-vacant outer orbital. If an atom gains an electron to become an anion, its radius grows, not only because of the space the electron occupies, but also because of the electron's added repulsive effects.

Question: 5

According to the First Law of Thermodynamics, the change in total energy of a system must:

A. Equal zero if the system is closed

B. Equal the sum of the system's changes in enthalpy and entropy

C. Be greater than zero

D. Be equal in magnitude but opposite in sign to the change in total energy of its surroundings

E. Include components of both heat and work

Answer: D

Explanation:

In other words, energy cannot be created or destroyed. A system's internal energy is comprised of its heat and work (done on or by the system). A system's internal energy may increase or decrease, but this must be matched by an opposite increase/decrease in the surroundings.

Question: 6

The following statements about mass and weight are all true, except:

A. Mass is an intrinsic property, while weight is the effect of gravity on the mass

B. Because mass is not subject to the effect of gravity, it is the preferred measurement for atoms, substances, and compounds

C. Mass and weight are essentially interchangeable

D. Mass remains constant no matter which planet you are on

E. An object will have more weight on the earth than on the moon

Answer: C

Explanation:

Though many people use "mass" and "weight" to refer to the same property, it is important to understand the distinction: mass is an intrinsic property of an object while weight is the pull of gravity on that object. Because weight varies with gravitational pull, it is not the preferred unit of measurement in chemistry.

Question: 7

Which of the following changes would you expect to drive the following reaction toward products? The reaction involves entirely gaseous species and is mildly exothermic.

CO + H2O ⇌ CO2 + H2

I. Increase the temperature from 300K to 450K

II. Remove CO2 from the reaction chamber as it is produced

III. Increase the pressure of H2O injected into the reaction chamber

IV. Decrease the partial pressure of CO

A. II and III

B. II, III, and IV

C. I only

D. I, II, and III

E. I and II

Explanation:

Answer: A

According to Le Châtelier's Principle, a change in equilibrium conditions leads to a shift in the equilibrium itself. You can shift a reaction toward products by increasing the amount of reactant or by removing some of the product. "Heat" can also be thought of as a factor in the equilibrium: a reactant in endothermic reactions, and a product in exothermic reactions. In this case, an increase in temperature is equivalent to increasing the amount of product and actually drives the reaction back toward reactants.

Question: 8

What would be a reasonable first step in balancing the following equation?

Pb(OH)4 + H2SO4 → Pb(SO4)2 + H2O

A. Create a table to track each element on both sides of the reaction

B. Adjust the coefficient of H2SO4

C. None of these

D. Adjust the coefficient of H2O

E. Any of these

Explanation:

Answer: A

There are many ways to balance reactions, all of which can produce the correct final answer. Some people find it helpful to write a tracking table; others can keep count in their heads. In this equation, it would be reasonable to start with the unequal numbers of S, H, or O and go from there.

Question: 9

To determine whether or not a reaction occurs between aqueous ions, you need:

A. Solubility rules

B. Bond energies

C. Gibbs Free Energies

D. pKa values

E. Electronegativities

Explanation:

Answer: A

If a pair of ions in solution can form an insoluble compound, this compound will precipitate (form a solid). If, however, all ion pairs are soluble, then they will continue to remain dissolved in solution, and no reaction will occur.

Question: 10

Which of the following behaviors could be reasonably expected of copper?

I. Lose 1 electron

II. Gain 1 electron

III. Lose 2 electrons

IV. Gain 2 electrons

A. III and IV

B. II and IV

C. I and III

D. III only

E. I and II

Explanation:

Answer: C

Copper, like most metals, has a positive oxidation state. This means that it wants to lose electrons; it is a reducing agent and therefore gets oxidized itself. Copper is one of the metals with multiple possible oxidation states (1+ or 2+).