Question

Incorrect statement/s among the following about alkynes is:

1. the first three members are gasses.
2. all alkynes are odourless.
3. all alkynes are colorless.
4. they are lighter than water and immiscible with water.

Answer 1

The incorrect statement about alkynes is that 'all alkynes are odourless.' While many alkynes are odorless, some can have odors, thus making this a false generalization.

Step-by-step explanation:

The incorrect statement about alkynes among the options given is that 'all alkynes are odourless.' While it is true that many alkynes are odorless, especially the simple ones such as acetylene, some alkynes do have odors. Now, let's address each statement provided:

1. The first three members of the alkyne series are indeed gases, which include ethyne (acetylene), propyne, and butyne.
2. It is incorrect to generalize that all alkynes are odourless, as chemical compounds can vary in odor based on their molecular structure and other substituents.
3. All alkynes are colorless, similar to alkanes and alkenes with the same carbon skeleton.
4. Alkynes are lighter than water and immiscible with it, due to their nonpolar nature and only having London dispersion forces as their intermolecular forces.

Therefore, the statement that 'all alkynes are odourless' is the incorrect one, as odors can vary among different alkynes.