1.

Which of the following compounds is an unsaturated hydrocarbon?

methane
*propyne
nonane
methyl

2.
The general name for hydrocarbons with at least one triple covalent bond is ____.

alkenes
alkyls
alkanes
*alkynes

3.
What is the name of the smallest alkyne?

butyne
*ethyne
methyne
propyne

4.
Which of the following is true about structural isomers?

Structural isomers have the same molecular formula.

Structural isomers have different physical and chemical properties.

Structural isomers have the same elemental composition.

*all of the above

5.
Alkanes do not have geometric isomers because the carbon atoms in their carbon-carbon bonds are ____.

double bonds
*quite polar
free to rotate
asymmetric

Thank you.

1. Propyne

2. Alkynes
3. Ethyne
4. All of the above
5. free to rotate

See your other post above.

The prefixes cis- and trans- are used to identify _____ isomers.

Name the 4 isomers of the compound with molecular formular c4h10o

#1-#4 are correct...#5 is actually FREE TO ROTATE. I just took the test.

1. To determine which compound is an unsaturated hydrocarbon, we need to understand the definition of unsaturated hydrocarbons. Unsaturated hydrocarbons are compounds that contain double or triple bonds between carbon atoms, while saturated hydrocarbons only contain single bonds.

Looking at the options provided:
- Methane (CH4) is a saturated hydrocarbon as it only contains single C-H bonds.
- Propyne (C3H4) has a triple bond between the second and third carbon atoms, making it an unsaturated hydrocarbon.
- Nonane (C9H20) is a saturated hydrocarbon as it only contains single C-H bonds.
- Methyl is not a specific compound but a functional group. So without further information, we can't determine if it's unsaturated or saturated.

Therefore, the compound that is an unsaturated hydrocarbon is propyne.

2. The general name for hydrocarbons with at least one triple covalent bond is alkynes. To arrive at this answer, we need to understand the nomenclature of hydrocarbons and the naming conventions for different types of bonds.

Hydrocarbons are compounds made up of only carbon and hydrogen atoms. Alkenes, alkanes, and alkynes are the three main groups of hydrocarbons that differ in the type of bond between carbon atoms. Alkenes have double bonds, alkanes have single bonds, and alkynes have triple bonds.

Based on this information, the correct answer is alkynes.

3. The smallest alkyne is ethyne. To determine this, we need to know the naming conventions for different carbon-carbon bonds in hydrocarbons.

Ethyne, also known as acetylene, has the chemical formula C2H2. It consists of two carbon atoms bonded together by a triple bond and has a hydrogen atom bonded to each carbon atom.

Therefore, ethyne is the smallest alkyne.

4. The correct statement about structural isomers is that "all of the above" are true. To understand this concept, we need to know what structural isomers are and how they differ from each other.

Structural isomers are compounds that have the same molecular formula (same number and types of atoms) but differ in the arrangement of atoms within the molecule. They have different structural formulas, meaning the atoms are bonded in alternative ways.

The given options state that "Structural isomers have the same molecular formula" (true since they only differ in structure), "Structural isomers have different physical and chemical properties" (true since their different structures lead to distinct properties), and "Structural isomers have the same elemental composition" (true since they have the same molecular formula).

Therefore, all of the above statements are true about structural isomers.

5. Alkanes do not have geometric isomers because the carbon atoms in their carbon-carbon bonds are free to rotate. To understand this concept, we need to know what geometric isomers and alkanes are.

Geometric isomers, also known as cis-trans isomers or stereoisomers, are compounds that have the same molecular formula and connectivity but differ in the arrangement of atoms in space due to the presence of restricted rotation around carbon-carbon bonds.

Alkanes are saturated hydrocarbons that only contain carbon-carbon single bonds. These single bonds allow free rotation around the carbon atoms, which means that the atoms can rotate freely without changing the connectivity or the arrangement in space.

As a result, alkanes cannot have geometric isomers because their carbon-carbon bonds are free to rotate. Geometric isomers are observed in compounds with restricted rotation, such as alkenes with double bonds or cyclic compounds.

Therefore, the correct answer is that alkanes do not have geometric isomers because the carbon atoms in their carbon-carbon bonds are free to rotate.