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Quiz Session - Attempts With Random Questions

College Chemistry Exam Questions

Page 8 of 25

141.

According to the Zeroth Law of Thermodynamics:

  • Two systems that are in thermal equilibrium must have the same temperature

  • Absolute zero is defined as 0 K or -273 C

  • The boiling point of water is defined as 373 K or 100 C

  • A closed system may be at a different temperature than its surroundings because it does not exchange any energy

  • Thermal equilibrium occurs when two systems may freely exchange heat, but no heat is being exchanged

Correct answer: Two systems that are in thermal equilibrium must have the same temperature

The Zeroth Law defines temperature as a concept without providing a scale for quantifying it. Though the other answer choices are all true, they are not part of the Zeroth Law.

142.

What is a strong electrolyte?

  • A compound that dissolves into soluble ions in aqueous solution

  • A compound that remains relatively intact (not dissolved) in aqueous solution

  • A strong acid or base (the terms are interchangeable)

  • A compound in aqueous solution that contains only covalent bonds

  • A compound in aqueous solution that contains only ionic bonds

Correct answer: A compound that dissolves into soluble ions in aqueous solution

By definition, an electrolyte produces ions in aqueous solution. However, some electrolytes are more readily dissolved than others. You can assume that a "strong electrolyte" (such as strong acids, strong bases, and soluble salts) dissolves fully in solution. However, a "weak electrolyte" may yield few ions in solution and should be assumed to be in its entire compound form, rather than its ion components.

143.

Consider the left side of an equation:

3Ba(OH)2 + H2O + NaCl --> ?

Before you balance the equation, you would need to account for the number of atoms on each side. How many H and O atoms are on the left side?

  • 8H, 7O

  • 8H, 8O

  • 5H, 4O

  • 4H, 3O

  • 12H, 11O

Correct answer: 8H, 7O

Be careful to include coefficients and subscripts when tallying atoms. Once you determined the products, you would need to balance the equation to ensure that there is the same number of each type of atom on both sides.

144.

What is the difference between a complete ionic equation and a net ionic equation?

  • The complete ionic equation contains all dissociated ions in a reaction; the net ionic equation contains only the ions that participate in the reaction

  • The complete ionic equation contains all dissociated ions in a reaction; the net ionic equation contains only the atoms that change oxidation states

  • The complete ionic equation contains only the ions that participate in the reaction; the net ionic equation contains all aqueous and solid state ions

  • The complete ionic equation is balanced with actual coefficients; the net ionic equation contains the lowest possible ratio of coefficients

  • The complete ionic equation is not balanced; the net ionic equation is balanced

Correct answer: The complete ionic equation contains all dissociated ions in a reaction; the net ionic equation contains only the ions that participate in the reaction

When soluble compounds are placed in solution together, some of the dissociated ions may react while others may "spectate." Net ionic equations are useful because they eliminate "spectator ions," allowing you to focus on the reaction at hand.

145.

All of the following statements about ions are true, except:

  • Carbon is a non-metal and is expected to gain four electrons to become C4-

  • Sodium is a metal and is expected to lose one electron to become Na+

  • Chlorine is a non-metal and is expected to gain one electron to become Cl-

  • Aluminum is a metal and is expected to lose either one or three electrons to become either Al+ or Al3+, respectively

  • Magnesium is a metal and is expected to lose two electrons to become Mg2+

Correct answer: Carbon is a non-metal and is expected to gain four electrons to become C4-

Though this scenario would theoretically produce an ion that fulfills the octet rule, it would create an ion with such an unstable charge that it cannot exist. When considering potential ions, it is important to think realistically about stability. For example, chlorine could theoretically gain one electron (Cl-) or lose seven electrons (Cl7+), but of course, the latter cannot form because it would be so unstable. In general, metals can form ions that are 1+, 2+, or 3+. Non-metals can form ions that are 1-, and larger non-metals can form 2- ions. Anything else is usually beyond the realm of stability.

146.

What type of reaction is occurring?

NH4+ + H2O ⇌ NH3 + H3O+

  • Hydrolysis

  • Oxidation

  • Reduction

  • Replacement

  • Synthesis

Correct answer: Hydrolysis

Hydrolysis is the process by which water breaks up another molecule. In this case, it occurs through an acid-base process in which water gains a proton from ammonium to produce the hydronium ion. Whenever acids/bases are in aqueous solution, you should assume that this is occurring, to some extent, in an equilibrium that depends on the relative acidities of the ions.

147.

What is the defining feature of an amine?

  • It is an ammonium derivative in which at least one H has been replaced by an alkyl group

  • It has a terminal -NH3

  • It has a terminal -NH2CH3 or NH3

  • It is an ammonium derivative in which 3-4 H atoms have been replaced by an alkyl group

  • It is an N atom bonded only to C, but not to H

Correct answer: It is an ammonium derivative in which at least one H has been replaced by an alkyl group

If you start with ammonium (NH4+) and subject it to alkylation, you can replace H with an alkyl group. This alkyl group may be as simple as a methyl (CH3) or much more complicated. Furthermore, you can replace each H in succession up to three times. Amines are referred to based on how many N-C bonds they contain: primary (one N-C bond), secondary (two N-C bonds), or tertiary (three N-C bonds).

148.

A molecule with the generic structure AX6 most likely adopts which electron configuration?

  • Octahedral

  • Trigonal pyramidal

  • Square planar

  • Trigonal planar

  • T-shaped

Correct answer: Octahedral

The six identical atoms are splayed out around the single unique atom, with 90 degrees between all atoms.

149.

The “sea of electrons” in a solid state substance is characteristic of:

  • Metallic solids

  • Ionic solids

  • Both ionic and metallic solids

  • Both molecular and metallic solids

  • Molecular solids

Correct answer: Metallic solids

Solid metals form crystalline structures that allow for overlapping orbitals. This means that many electrons flow freely between atoms, making metals excellent conductors of electricity. In contrast, ionic solids conduct electricity in the liquid/aqueous state. Most molecular solids do not conduct electricity.

150.

In general, the strongest bonds are associated with:

  • Short bond lengths and high bond energies

  • Short bond lengths and low bond energies

  • Longer bonds and high bond energies

  • Longer bonds; the bond energies are variable

  • High bond energies; the bond lengths are variable

Correct answer: Short bond lengths and high bond energies

Strong bonds form because there is a strong electrostatic attraction between atoms. They, therefore, are more stable when they are closer together, so bonds are usually shorter. In addition, it takes more energy to overcome that attraction and break the bond.

151.

Ammonia, or NH3, is not planar. What structure do you expect ammonia to have?

  • Trigonal pyramidal 

  • Trigonal planar

  • Bent

  • Seesaw

  • Square pyramidal

Correct answer: Trigonal pyramidal 

While some molecules with four atoms are planar (for example, SO3), NH3 forms a pyramid structure because the electron pair on Nitrogen pushes the single N-H bonds away, bending them out of the plane. When figuring out the molecular geometry, it is important to know two things: how many atoms are attached to the central atom, and how many lone pairs are on the central atom.

152.

What is wrong with the following equation?

Na(s) + HCl(aq) → NaCl(aq) + H2(g)

  • It is not written as a balanced equation

  • It should have a double-ended (equilibrium) arrow

  • It should take place entirely in aqueous solution

  • It cannot take place in aqueous solution

  • It involves improbable oxidation states

Correct answer: It is not written as a balanced equation

There is nothing chemically wrong with this equation. However, as written, there is only one H atom on the left and two H atoms on the right. The balanced equation is:

2Na(s) + 2HCl(aq) → 2NaCl(aq) + H2(g)

153.

Based on standard nomenclature, what is Al(OH)3 called?

  • Aluminum hydroxide

  • Aluminum trihydroxide

  • Aluminum oxyhydride

  • Alumide trihydroxide

  • Alumide oxyhydride

Correct answer: Aluminum hydroxide

In a binary, metal-ion compound, the metal keeps its name while the ion takes the suffix -ide. It is important to realize that the OH group is the ion hydroxide, and is therefore named as a unit (not as individual atoms, as would be implied by "oxyhydride"). The number of units is not included in the name. It is implied that the compound has a neutral net charge, and since aluminum tends to form the 3+ ion, we can infer that there must be three hydroxide groups with a 1- charge each.

154.

What coefficients would balance the following reaction?

__FeS + __O2 → __Fe2O3 + __SO2

  • 4, 7, 2, 4

  • 2, 7, 2, 4

  • 4, 6, 3, 2

  • 2, 7, 1, 4

  • 2, 5, 3, 2

Correct answer: 4, 7, 2, 4

This reaction is challenging because oxygen appears so many times. Start with the non-oxygen atoms:

2FeS + __O2 → __Fe2O3 + 2SO2 

Now there are only two oxygens on the left but seven on the right. Therefore, to be balanced, the reaction requires 14 oxygens on either side (14 is the least common multiple of 2 and 7):

2FeS + 7O2 → 2Fe2O3 + 4SO2 

This adjustment increased the number of Fe and S, so the last step is to adjust this:

4FeS + 7O2 → 2Fe2O3 + 4SO2

155.

Which of the following properties do you not expect to find together?

  • Weak surface tension and high boiling point

  • High boiling point and hydrogen bonding

  • Multiple -OH groups and strong surface tension

  • Nonpolar organic molecule and low boiling point

  • Strong intermolecular forces and strong cohesive forces

Correct answer: Weak surface tension and high boiling point

Many predictions can be made on the basis of a molecule's attraction to other identical molecules ("intermolecular forces"). When there are strong intermolecular forces (e.g., hydrogen bonding that involves H attached to N, O, or F), you should expect strong cohesive forces, strong surface tension, and high melting/boiling points. When there are weak intermolecular forces (e.g., a nonpolar organic molecule), you should expect the opposite.

156.

What force does mass spectrometry use to separate atoms?

  • Magnetism

  • Electricity

  • Chemical bonds

  • Nuclear radiation

  • UV rays

Correct answer: Magnetism

Mass spectrometry (also known as mass spectrography) uses a magnetic field to bend the path of atoms accelerated by an electron beam. The atoms with smaller mass arc on a wider path, while atoms with larger mass are pushed less off-course by the magnetic field. This causes atoms to separate by mass by the time they reach the photographic plate.

157.

Which of the following is the correct way to double the formula for water?

  • 2H2O

  • H4O2

  • H2O2

  • 2(H2)O

  • H4O4

Correct answer: 2H2O

When balancing equations, increase the number of molecules by placing a coefficient in front of the formula. It's important to avoid changing the molecular formula when balancing equations!

158.

H2O2 → H2O + O2

What volume O2 gas is produced from 1.90mol H2O2 at STP?

  • 21.3L

  • 42.6L

  • 28.4L

  • 37.9L

  • 11.0L

Correct answer: 21.3L

First, balance the equation: 2H2O2 → 2H2O + O2

At STP, all gases can be assumed to occupy 22.4L/mol. Therefore:

(1.90mol H2O2) * (1mol O2 / 2mol H2O2) * (22.4L O2 / 1mol O2) = 21.3L O2

159.

According to the Kinetic Molecular Theory of gases, a gas's average kinetic energy (KE) is defined as:

  • KE = (1/2)mv2 = (3/2)kbT

  • KE = (1/2)mv2

  • KE = 2mv2

  • KE = (1/2)mv2 = (1/2)kbT

  • KE = 2mv2 = (3/2)kbT

Correct answer: KE = (1/2)mv2 = (3/2)kbT

Kinetic Molecular Theory relates a gas's kinetic energy (KE) to its temperature, using the Boltzmann constant (kb). Importantly, this equation does not define the KE of any one gas molecule, nor does it claim that temperature determines the KE of any single molecule. Rather, temperature increases the average KE and therefore average velocity within the gas.

160.

For a first-order reaction, if you plot the natural log of the reactant concentration against the time of reaction, what mathematical model should fit your plot?

  • Linear

  • Quadratic

  • Exponential

  • Logarithmic

  • Logistic

Correct answer: Linear

A first-order reaction depends only on the concentration of reactant, so it has rate = k1[A]. ;Solving this equation, you get ln[A] = -kt + ln[A]0. This is a linear equation with slope -k and y-intercept ln[A]0, or the natural log of the initial concentration of reactant A.

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