Question 1

Which of the following is a saturated molecule?

Accepted Answer

The answer of Which of the following is a saturated...

Question 2

Which of the following statements best describes the effect of heteroatoms on hydrocarbons?

Accepted Answer

Heteroatoms, which are atoms other than carbon and hydrogen, can greatly affect the chemical and physical properties of a hydrocarbon. For example, adding an oxygen atom to a hydrocarbon can make it more polar and increase its boiling point. Adding a nitrogen atom can create functional groups such as amines or amides, which can greatly alter the reactivity of the molecule. Therefore, heteroatoms have a significant impact on hydrocarbons.

Question 3

How many structural isomers are shown here?

Accepted Answer

There are two structural isomers shown in the image. One is a straight chain alkane with five carbon atoms, while the other is a branched chain alkane with four carbon atoms and a methyl group attached to the second carbon atom.

Question 4

Which of the above sections of this molecule would be considered a saturated portion of the molecule?

Accepted Answer

The portion of the molecule that is considered "saturated" is one that contains only single covalent bonds between the carbon atoms. In this case, only section C fits this description, as it contains only single bonds between the carbon atoms. Sections A and B contain at least one double bond between carbon atoms, making them unsaturated. Therefore, choice C is the correct answer.

Question 5

Which of the following is a heteroatom?

Accepted Answer

Heteroatoms are atoms other than carbon and hydrogen that are present in an organic molecule. Oxygen (O) is a heteroatom, while carbon (C) and hydrogen (H) are not. Therefore, the correct answer is A) O.

Question 6

Which of the above sections of this molecule would be considered an unsaturated portion of the molecule?

Accepted Answer

Unsaturated portions of a molecule contain double or triple bonds between carbon atoms. Both sections a and b would have such bonds, making them unsaturated.

Question 7

What is the chemical formula for the following structure?

Accepted Answer

The given structure contains a total of 6 different atoms: carbon (C), sulfur (S), hydrogen (H), and oxygen (O) as indicated by the different colors. Using the given color code, we can count the number of atoms of each type present in the structure and write the chemical formula accordingly. The correct formula is C₇H₁₂, which matches option C. Option A and B have incorrect numbers for some of the atoms. Option D has an incorrect number of sulfur atoms.

Question 8

Which two of these four structures are of the same structural isomer?

Accepted Answer

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Question 9

Which of the following is not an unsaturated molecule?

Accepted Answer

Molecule D has only single bonds between all of its atoms, which makes it a saturated molecule. Molecules A, B, and C all have at least one double bond, making them unsaturated. Therefore, the correct answer is D.

Question 10

Which of the above sections of this molecule would be considered to be the aromatic portion of the molecule?

Accepted Answer

The answer of Which of the above sections of this...

Question 11

What is indicated by a gasoline's octane rating?

Accepted Answer

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Question 12

Why does the melting point of hydrocarbons increase as the number of carbon atoms per molecule increases?

Accepted Answer

The answer of Why does the melting point of hydrocarbons...

Question 13

Which of the following is an aromatic molecule?

Accepted Answer

The answer of Which of the following is an aromatic...

Question 14

Which of the following is not a heteroatom?

Accepted Answer

Heteroatoms are atoms other than carbon and hydrogen that are present in an organic compound. Oxygen (O), nitrogen (N), and phosphorus (P) are all considered heteroatoms because they are commonly found in organic compounds but are not carbon or hydrogen.

Question 15

In a fractionating tower, the crude oil vapors pass from a pipe still into the column. Tar and lubricating stock are the first components to be pulled off at the bottom. Nearer the top kerosene is pulled off followed by gasoline and finally natural gas at the very top. From this information, which has a higher boiling point, gasoline or kerosine?

Accepted Answer

In a fractionating tower, components with higher boiling points are pulled off lower down in the column. Since kerosene is pulled off before gasoline, it must have a higher boiling point.

Question 16

Carbon-carbon single bonds can rotate while carbon-carbon double bonds cannot rotate. How many different structures are shown below.

Accepted Answer

There are three different structures shown in the image, each with a different arrangement of the carbon-carbon single bonds. The double bond cannot rotate, so it does not contribute to the number of unique structures.

Question 17

Which of the following is the hallmark of a saturated hydrocarbon?

Accepted Answer

A saturated hydrocarbon is one where all carbon atoms have only single bonds to other atoms, whether carbon or hydrogen. Such a structure is said to be "saturated" with hydrogen atoms because there are no double or triple bonds available for other atoms to bond with. This distinguishes saturated hydrocarbons from unsaturated hydrocarbons, which have one or more double or triple bonds between carbon atoms.

Question 18

The temperatures in a fractionating tower at an oil refinery are important, but so are the pressures. Where might the pressure in a fractional distillation tower be greatest, at the bottom or at the top? Defend your answer.

Accepted Answer

The pressure is directly proportional to the number of vaporized molecules. Since the temperature is higher at the bottom of the tower, there will be a greater number of vaporized molecules, leading to a higher pressure at the bottom.

Question 19

What property of carbon allows for the formation of so many different organic molecules?

Accepted Answer

Carbon has the unique ability to form strong covalent bonds with other carbon atoms, as well as with a variety of other elements such as oxygen, nitrogen, and sulfur. This allows for the formation of countless structures with different functional groups and properties, giving rise to the vast diversity of organic molecules found in nature.

Question 20

Which of the following does not describe the number of other atoms a carbon atom can be bonded to?

Accepted Answer

A carbon atom cannot form more than four covalent bonds, so it cannot be bonded to five other atoms. Therefore, option D (only 5) does not describe the number of other atoms a carbon atom can be bonded to.

Quiz 19: Organic Compounds