AP Chemistry : AP Chemistry

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #65 : Thermodynamics

A chemistry student is trying to calculate how long it will take a power source of  to heat a  sample of ice from  to . Given that the specific heat capacity of ice is , the specific heat capacity of liquid water is , and the heat of fusion for water is , how long will this process take?

Possible Answers:

There is not enough information to determine the amount of time needed for the process described

Correct answer:

Explanation:

In order to solve this problem, we'll need to break it up into steps.

 

Step 1: Calculate the amount of energy necessary to raise the sample of ice from  to . To do this, we'll need to use the following equation:

 

Step 2: Calculate the amount of energy necessary to convert the sample at  from ice to water. We'll need to make use of the following equation:

 

Step 3: Calculate the amount of energy necessary to convert the sample of water from  to .

 

Step 4: Sum the amount of energy from the previous 3 steps. This value is the total amount of energy for the entire process.

 

Step 5: Now that we know the total amount of energy needed for the process, we need to calculate the time based on the amount of power provided.

Example Question #1 : Other Bonding Concepts

Which of the following compounds contains the most π bonds?

Possible Answers:

H2O

C2H6

CH4

NH3

CO2

Correct answer:

CO2

Explanation:

π bonds occur when there is greater than a single bond (double or triple bond). The only compound listed with double bonds or greater is CO2, meaning it is the one that contains the most π bonds.

Example Question #1 : Other Bonding Concepts

Which of the following compounds has the greatest amount of sigma bonds?

Possible Answers:

Butane

Water

Ethane

Benzene

Lithium Hydroxide

Correct answer:

Butane

Explanation:

Butane has 13 sigma bonds. Ethane has 7 sigma bonds. Benzene has 12 sigma bonds. Lithium Hydroxide has 2 sigma bonds and water has 2 sigma bonds.

Example Question #2 : Other Bonding Concepts

Which of the following bonds is the strongest?

Possible Answers:

Triple bond

Coordinate covalent bond

Double bond

Single bond

Correct answer:

Triple bond

Explanation:

Triple bonds involve sharing a total of six electrons. They are shortest in length and store the most energy, making them difficult to break. These properties make triple bonds stronger than double or single bonds.

Coordinate covalent bonds form when one atom contributes two electrons to be shared between nuclei, as opposed to each atom sharing a single electron. Once formed, coordinate covalent bonds have essentially identical properties to any other single bonds.

Example Question #4 : Other Bonding Concepts

Of the following molecules, which do you predict will have the shortest distance between the two atomic nuclei?

Possible Answers:

Correct answer:

Explanation:

Diatomic nitrogen, , contains a triple bond between the two nitrogen atoms. Since there are six electrons being shared, the bond is stronger and the atoms are being pulled closer together. Diatomic oxygen, ,  has a double bond, which is not as strong. Diatomic hydrogen, , has a single bond, which have a bond length greater than either a double or triple bond. Hydrochloric acid, , is an ionic compound and will have a bond length comparable to a single covalent bond.

Example Question #3 : Other Bonding Concepts

What types of bonds are found in a single molecule of the following compound?

Ag(NH3)3

I. Covalent

II Hydrogen

III. Ionic

Possible Answers:

II, III

I, III

III only

I, II

I only

Correct answer:

I, III

Explanation:

Ag(NH3)3 has covalent bonds (N-H) and ionic bonds (Ag-N).

A hydrogen bond is an intermolecular force between a hydrogen atom and an electronegative atom (O, N, F) that are in close proximity. Hydrogen bonds can occur within a given molecule (intramolecular), but more commonly occur between adjacent molecules (intermolecular). A solution of Ag(NH3)3 would show hydrogen bonding between the hydrogen and nitrogen of nearby molecules. The compound would not show intramolecular hydrogen. Since the question asks only for intramolecular interactions (single molecule), hydrogen bonding cannot be an answer choice.

Example Question #6 : Other Bonding Concepts

Figure 1: Ammonia gas formation and equilibrium

 

Oxygen, hydrogen, and nitrgoen form diatomic molecules in their natural states. What is the order of these molecules by bond length?

Possible Answers:

O2 < N2 < H2

N< H2 < O2

O2 < H2 < N2

H2 < O2 < N2

N2 < O2 < H2

Correct answer:

N2 < O2 < H2

Explanation:

We know from Lewis structures that diatomic hydrogen will have a single bond, diatomic oxygen will have a double bond, and diatomic nitrogen will have a triple bond. Triple bonds are stronger than double or single bonds, and the stronger the bond, the shorter the bond length. Nitrogen will have the shortest bond length.

We also know that the longest bond will be weakest. This mean hydrogen, with its single bond, would have the longest bond length. The answer should be N2 < O2 < H2.

Example Question #7 : Other Bonding Concepts

Which of the following functional groups contains only central atoms with  hybridization?

Possible Answers:

Ketone

Alcohol

Carboxylic acid

Ester

Aldehyde

Correct answer:

Alcohol

Explanation:

Out of the five given functional groups, only alcohols do not contain a central atom which is double bonded (meaning those atoms have  hybridization). The only central atom of an alcohol, the oxygen atom in , has single bonds to the R-group and a single hydrogen along with two lone pairs, giving it  hybridization.

Example Question #8 : Other Bonding Concepts

Which of the following types of organic compounds has  hybridization?

Possible Answers:

Carboxylic acid

Alkane

Alkene

Ketone

Alkyne

Correct answer:

Alkyne

Explanation:

The alkyne, a hydrocarbon containing a triple bond, has one sigma  bond, and two pi bonds, making a rod-like molecule with a bond angle of  and  hybridization. It is the only type of compound of the choices to have a triple bond, making it the only possibility.

Example Question #8 : Other Bonding Concepts

What is the bond angle and molecular geometry formed by the atoms in brackets in the molecular formula above?

Possible Answers:

; trigonal planar

; tetrahedral

; tetrahedral

; trigonal pyramidal

; bent

Correct answer:

; trigonal planar

Explanation:

The  group indicated by the question consists of a carbon atom bonded to two oxygen atoms (one with a double bond, and one with a single bond). The carbon is also bonded to the rest of the hydrocarbon chain by a single sigma bond. Because this carbon atom only has three electron domains and has no lone pairs, trigonal planar is the molecular geometry that best describes this piece of the larger molecule. The atoms bonded to this carbon molecule sit at  from each other, an even division of the single plane in which these atoms sit. 

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