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Quiz Session - Attempts With Random Questions

College Chemistry Exam Questions

Page 6 of 25

101.

What are the oxidation states of each atom in the following molecule?

Zn(OH)42- 

  • Zn = +2, O = -2, H = +1

  • Zn = 0, O = -2, H = +1

  • Zn = -2, O = -1, H = +1

  • Zn = +6, O = -2, H = 0

  • Zn = +2, O = -1, H = 0

Correct answer: Zn = +2, O = -2, H = +1

Always start with O and H, as these have predictable oxidation states of -2 and +1, respectively. Then calculate what Zn must be to produce an overall charge of -2:

-2 = Zn + 4(-2 + 1)

-2 = Zn - 4

+2 = Zn

102.

What is an allotrope?

  • One of multiple different physical forms of the same element

  • An atom that contains a different number of neutrons from another atom of the same type

  • A compound that can be both acidic and basic

  • A symmetrical compound

  • An atom that can lose or gain electrons with equal propensity

Correct answer: One of multiple different physical forms of the same element

For example, carbon can hybridize with itself in a variety of ways. This leads to substances as different as diamond and graphite: both pure carbon but with very unique physical properties.

103.

On what basis does ion exchange chromatography separate molecules?

  • Charge

  • Size

  • Number of ionic bonds

  • Acidity/basicity

  • Number of electrons

Correct answer: Charge

An ion exchange column is filled with resin that is charged oppositely from the molecules in the mixture that you wish to separate. When the mixture passes through the column, your molecules of interest are attracted and bind to the resin, remaining in the column. Then, you pass increasingly charged salt solutions through the column, and the salts displace molecules from your original mixture, causing these molecules to elute. The timing of elution is determined by how much charge each molecule has.

104.

Mass spectrometry is useful for separating which of the following?

  • Atoms with different masses

  • Ions with different charges

  • Compounds with different boiling points

  • Liquids with different freezing points

  • Electrons with different velocities

Correct answer: Atoms with different masses

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. Mass spec is particularly useful for identifying and separating isotopes, which vary by mass but not by charge.

105.

Under what conditions is the Ideal Gas Law the least accurate?

  • Low temperatures and small volumes

  • Small volumes and high pressures

  • High temperatures and high volumes

  • Low temperatures and low pressures

  • The Ideal Gas Law is accurate regardless of condition

Correct answer: Low temperatures and small volumes

The Ideal Gas Law (PV=nRT) assumes that gas molecules occupy zero space and do not interact with each other. In small volumes, the space occupied by gas molecules becomes much more consequential in the context of the container's overall volume. At low temperatures, the gas molecules move slowly enough to interact more significantly. The van der Waals equation can be used under these suboptimal conditions to predict gas behaviors more accurately.

106.

Manganese has five electrons in its 3d subshell. How many orbitals do these five electrons occupy?

  • 5

  • 4

  • 3

  • 2

  • 1

Correct answer: 5

According to the Principle of Maximum Multiplicity, electrons occupy separate orbitals until there are no empty orbitals left, and then they pair up. Since the 3d subshell has five orbitals, the first five electrons will fill all five of these orbitals.

107.

You add NaCl, CaCl2, and HCl all together in solution. What phenomenon should you consider when evaluating solubility?

  • Common ion effect

  • Salt effect

  • Diverse ion effect

  • Solubility product constant effect

  • Acid effect

Correct answer: Common ion effect

When multiple compounds contribute the same ion (in this case, Cl-) to solution, the solubility of each individual compound is reduced. This is opposite from the diverse ion effect, or salt effect, in which an uncommon ion in solution increases the solubility of the other main ions.

108.

Au+ and Au3+ differ significantly in terms of their:  

  • Oxidation states

  • Atomic mass

  • Atomic radius

  • Metallic character

  • Malleability

Correct answer: Oxidation states

The charge on an ion is the same as its oxidation state. Some metals, such as gold, iron, and copper, can form multiple oxidation states. This alters the ion's bonding behavior but doesn't significantly affect its mass, atomic radius, or physical properties.

109.

Which of the following are acceptable names for HF?

i. Hydrofluoride

ii. Hydrofluoric acid

iii. Hydrogen fluoride

iv. Hydrogen fluorine

  • ii. and iii.

  • i., ii., and iii.

  • i., iii., and iv.

  • ii. only

  • i. and ii.

Correct answer: ii. and iii.

HF may be named as a binary compound (hydrogen fluoride) or as a binary acid (hydrofluoric acid). It is useful to be familiar with both types of nomenclature, and use whichever is most appropriate in the context. For example, when discussing acid-base reactions, "hydrofluoric acid" makes the most sense.

110.

Tin (Sn) and lead (Pb) are both Group 14 elements, in the same group as carbon. What oxidation states do you expect them to form readily?

  • +2 and +4

  • Any state from -4 to +4

  • Any state from 0 to +4

  • -2 and +2

  • +2 only

Correct answer: +2 and +4

This mirrors the ions that form readily: tin-II, tin-IV, lead-II, and lead-IV. These elements have the valence electron configuration ns2p2, so they gain the most stability by losing either two or four electrons.

111.

In which block of the periodic table are you most likely to find an element that forms multiple oxidation states?

  • d-block

  • s-block

  • p-block

  • s-block and p-block equally

  • p-block and d-block equally

Correct answer: d-block

Transition metals often can form multiple oxidation states, though they usually are most stable in one state consistently. For example, manganese forms every state from -3 to 7 but is most stable in +2.

112.

You make a glass of ice water. What is unusual about this particular mixture of solid and liquid states?

  • The ice floats

  • Condensation collects on the sides

  • After a few minutes, the water reaches the same temperature as the ice

  • The water/ice combination stays cold for a long time

  • The water does not increase in temperature until after all of the ice has melted

Correct answer: The ice floats

For almost all elements and molecules in the world, the solid state is denser than the liquid state. If this were true for water, ice would sink to the bottom of your glass, and the polar ice caps would sink to the bottom of the ocean. This peculiar property is attributable to solid water's hexagonal lattice structure, which is relatively spread out and actually keeps molecules spaced further apart than they are in liquid water.

113.

What is Avogadro's number?

  • 6.023 x 1023

  • 6.023 x 1020

  • 6.23 x 1023

  • 6.23 x 1020

  • 6.0023 x 1021

Correct answer: 6.023 x 1023

This is the amount of a substance that contains the same number of fundamental particles (atoms, compounds, etc.) as there are atoms in 12.000g of Carbon-12. Avogadro's number is the same for any chemical substance you might want to work with, and is therefore important to commit to memory!

114.

Which factor(s) affect the rate of zero-order reactions?

i. Concentration of reactant(s)

ii. Concentration of product(s)

iii. The conditions in which the reaction occurs

  • iii. only

  • i. only

  • i. and iii.

  • ii. and iii.

  • i., ii., and iii.

Correct answer: iii. only

A zero-order reaction is unique in that its rate is not at all influenced by the concentration of reactants. Instead, the rate is dictated by the rate coefficient k, which depends on various environmental conditions like temperature.

115.

Keeping in mind that this molecule involves nitrogen forming covalent bonds with both oxygen atoms (one single bond and one double bond) and carrying a single lone electron, what are the molecular and electron geometries of nitrogen dioxide?

  • Molecular = bent, electron = trigonal planar

  • Molecular = bent, electron = tetrahedral

  • Molecular = linear, electron = trigonal planar

  • Molecular = linear, electron = trigonal pyramidal

  • Molecular = trigonal planar, electron = trigonal pyramidal

Correct answer: Molecular = bent, electron = trigonal planar

Just like water, nitrogen bonds with oxygen atoms that are splayed out in a bent configuration. The single lone electron is oriented as far away from the covalent bonds as possible. Since nitrogen has three electron units (two covalent bonds and one lone electron), these units adopt the trigonal planar configuration.

116.

Predict the products of the following reaction (don't worry about balancing):

K3PO4 (aq) + Al(NO3)3 (aq) →  ?

  • AlPO4 (s) + KNO3 (aq)

  • KNO3 (s) + AlPO4 (aq)

  • AlPO4 (aq) + KNO3 (aq)

  • Al3+ (s) + PO43- (aq) + K+ (aq) + NO3- (aq)

  • No reaction

Correct answer: AlPO4 (s) + KNO3 (aq)

According to solubility rules, phosphates are insoluble unless paired with ammonia, potassium, or sodium. Therefore, the potassium phosphate reactant is soluble, but the aluminum phosphate product precipitates out.

117.

When balancing ionic equations, you are taught to write "half-reactions." On what basis do you divide the reaction in half?

  • Oxidation/reduction

  • Reactants/products

  • Acids/bases

  • Metals/non-metals

  • Ionic/covalent

Correct answer: Oxidation/reduction

You will write one reaction that contains the oxidation process and a separate reaction that contains the reduction process. Once atoms and charge are balanced, you re-combine the equations for the final result.

118.

H2SO4 is called sulfuric acid. What is the formula for sulfurous acid?

  • H2SO3

  • H2SO5

  • H2SO2

  • HSO4

  • HSO3

Correct answer: H2SO3

Based on standard nomenclature, the oxyacid with the most oxygen atoms is called the "-ic" acid, while the acid with the next-most oxygen atoms is the "-ous acid." To convert between the formulas, simply add or remove an oxygen.

119.

What is the SI unit for current?

  • Ampere

  • Kelvin

  • Candela

  • Coulomb

  • Volt

Correct answer: Ampere

The other answer choices are all SI units, however: Kelvin = temperature, Candela = luminosity, Coulomb = electric charge, Volt = electric potential.

120.

In the following chemical formula, how many atoms of each species are present?

3Ba(OH)2

  • Three Ba, six O, six H

  • Three Ba, two O, two H

  • Three B, three a, six O, six H

  • Three B, three a, two OH

  • Three Ba, two OH

Correct answer: Three Ba, six O, six H

The atoms involved here are Ba (barium), O (oxygen), and H (hydrogen). Remember that atomic symbols may come as a single capital letter or a pair of letters (one capital, one lower case). Once you have identified the atoms correctly, remember that the coefficient (in this case, 3) applies to the entire molecule. The subscript (in this case, 2) applies only to the atom or set of parenthesis preceding it.

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