College Chemistry : Introductory Topics

Study concepts, example questions & explanations for College Chemistry

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Example Questions

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Example Question #1 : Molecules And Compounds

In an ionic bond, electrons are __________

Possible Answers:

repelled

destroyed

excited

shared 

transferred

Correct answer:

transferred

Explanation:

In an ionic bond, electrons are transferred to make a compound. For example, a sodium atom and a chloride atom can combine, exchanging electrons to form:  and  in solution, or  (sodium chloride/table salt). Electrons are shared only in covalent bonds. Electrons can be repelled if two (or more) electrons are within very close proximity of one another. Electrons can be excited by absorbing energy and then subsequently jumping from the ground state to a higher, less stable state. Electrons may never be destroyed and/or created.

Example Question #1 : Molecules And Compounds

Which of these can be formed when ionic bonds break down?

Possible Answers:

Micelle

None of these; ionic bonds never break down.

Lattice structure

Cation

Correct answer:

Cation

Explanation:

Ionic bonds are bonds involving the attraction between oppositely-charged ions. An example of an ionic compound is , or table salt. The sodium is positively-charged, while the chlorine is negatively-charged. These opposite charges attract via an ionic bond to form the ionic compound . When this ionic bond breaks, the sodium and chlorine separate into ions:  (the positively-charged cation) and  (the negatively-charged anion).

Ionic compounds have a characteristic lattice structure--that is, the arrangement of ions in a regular, geometric pattern. In the case of , this structure simply refers to the arrangement of  and  ions in a pattern to form . It forms when an ionic compound is being created, not broken down.

Lastly, micelles are lipid molecules which, in aqueous solution, arrange themselves in a spherical form. This is a response to the fact that fatty acids have both hydrophilic and hydrophobic regions (they are amphipathic). It has nothing to do with ionic bonds.

Example Question #1 : Ionic Bonds

What is the molecular formula for aluminum sulfide?

Possible Answers:

Correct answer:

Explanation:

Sulfur is much more electronegative than Aluminum (a metal), so when they bond they form an ionic compound as Aluminum transfers its electrons to Sulfur. Aluminum has a valence of 3, meaning that each Aluminum atom is looking to share or transfer 3 electrons to achieve a stable configuration. Sulfur has a valence of 6, meaning that each Sulfur atom is looking for two electrons to complete its octet. Thus, two Aluminum atoms will bond with three Sulfur atoms, resulting in the transfer of six electrons in total.

Example Question #1 : Introductory Topics

What is the charge on the cation in the ionic compound sodium oxide?

Possible Answers:

Correct answer:

Explanation:

When sodium and oxygen form the ionic compound sodium oxide, , each sodium ion transfers an electron to the central oxygen atom. Thus, each sodium atom becomes a positive ion (or cation) with a charge of +1.

Example Question #1 : Molecules And Compounds

Which of the following is a characteristic of covalent bonds?

Possible Answers:

Covalent compounds are good conductors of electricity.

A covalent bond is one between two nonmetals.

A covalent bond is one between a metal and a nonmetal.

Covalent compounds dissolve in water to form cations and anions.

Correct answer:

A covalent bond is one between two nonmetals.

Explanation:

A covalent bond is one between two nonmetals, while an ionic bond is formed between a metal and a nonmetal. Covalent bonds also do not dissociate in aqueous solution to form cations and anions; this is a characteristic of ionic bonds. For example,  represents a bond between a metal () and a nonmetal (), and it dissociates in aqueous solution to form a cation () and an anion (). In contrast,  represents a bond between two nonmetals, and it does not dissociate in aqueous solution. Ionic compounds are also good conductors of electricity, while covalent compounds are not. This is because moving electrons are required in order to conduct electricity. When dissolved in aqueous solution, ions are free to move and thus conduct electricity. Covalent bonds have localized electrons, which cannot move and thus cannot conduct electricity well.

Example Question #191 : College Chemistry

Which of the following is an example of a nonpolar covalent bond?

Possible Answers:

Correct answer:

Explanation:

A covalent bond is a bond between two nonmetals, in which electrons are shared. This means that  cannot be the correct answer, as sodium is a metal. In fact,  is a classic example of an ionic compound.

A polar covalent bond is a bond between two nonmetals in which one nonmetal is more electronegative than the other, pulling the shared electrons toward itself. This occurs in ; chlorine is much more electronegative than hydrogen and pulls the shared electrons toward itself. This gives chlorine a partial negative charge and hydrogen a partial positive charge.  is also an example of a polar covalent bond; oxygen is much more electronegative than hydrogen, and each oxygen in a water molecule pulls the shared electrons toward itself. This gives oxygen a partial negative charge and hydrogen a partial positive charge. 

A nonpolar covalent bond is a bond between two nonmetals in which electrons are shared equally between the nonmetals. This occurs when the two nonmetals are of equal electronegativity. As the atoms of  have the same identity (chlorine), they have the same electronegativity. Thus, electrons are shared equally between the two chlorine atoms--in a nonpolar covalent bond.

Example Question #1 : Covalent Bonds

Which of the following compounds contains  covalent bonds?

Possible Answers:

Correct answer:

Explanation:

For this question, we're asked to determine which answer choice represents a compound with a total of six covalent bonds.

To answer this, we'll need to know the structure of each of the compounds. Moreover, it's important to remember that double bonds count as two covalent bonds.

Both sulfuric acid and phosphoric acid have a total of eight covalent bonds, while nitric acid has five. Carbonic acid is the only one shown that contains six covalent bonds, making it the correct answer.

Example Question #1 : Covalent Bonds

Which of the following lists bond strength in order of weakest to strongest?

Possible Answers:

Dipole-dipole, covalent, hydrogen, ionic

Hydrogen, dipole-dipole, ionic, covalent

Covalent, ionic, hydrogen, dipole-dipole

Dipole-dipole, ionic, hydrogen, covalent

Dipole-dipole, hydrogen, covalent, ionic

Correct answer:

Dipole-dipole, hydrogen, covalent, ionic

Explanation:

Dipole-dipole interactions are the weakest because they are the result of attractions between weak partial charges

Hydrogen bonds are a special type of dipole-dipole interaction, but they are much stronger. 

An ionic bond is the result of the complete transfer of electrons from on atom to another. This results in a positive charge on one atom and a negative charge on the other. The charges on these ions are much stronger than in dipoles. The two oppositely charged atoms are held together by electrostatic attraction.  

Atoms that are part of a covalent bond share electrons. This makes the atoms harder to separate and, therefore, the bond is very strong.

Example Question #1 : Molecules And Compounds

Which of these following diatomic molecules is joined by a double covalent bond?

Possible Answers:

Correct answer:

Explanation:

Oxygen has a valence of 6, meaning it is looking to form two covalent bonds to complete its octet. Thus,  exists as a diatomic molecule joined by a double covalent bond.  and  are held together by single covalent bonds, and  is held together by a triple covalent bond. 

Example Question #1 : Intermolecular And Intramolecular Forces

Which of the following best explains the main difference between strong and weak acids or bases? 

Possible Answers:

Strong acids and bases are more concentrated than weaker ones

Strong acids and bases always have multiple protons to donate or accept

Weak acids and bases dissociate completely in water

None of these

Strong acids and bases ionize completely in water whereas weak ones do not

Correct answer:

Strong acids and bases ionize completely in water whereas weak ones do not

Explanation:

Molarity has no determination in whether an acid or base is strong or weak. Rather, molarity specifies the concentration of hydroxide or hydrogen ions in a solution. Weak Acids do not completely dissociate in water, while strong acids do. Polyprotic acids, those with more than one proton to donate, do not necessarily determine if an acid is strong (e.g. hydrochloric acid is an example of a strong, monoprotic acid). 

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