Consider the four hydrocarbons in the table below. One is an alkyne, and the other three are alkenes.

| Hydrocarbon | Boiling point (°C) |
|-------------|---------------------|
| W | -23.0 |
| X | -103.7 |
| Y | -75.0 |
| Z | -47.0 |

If these hydrocarbons were similar in size, which one would most likely be an alkyne?

A. W
B. X
C. Y
D. Z



Answer :

In the given problem, we are provided with the boiling points of four hydrocarbons: W, X, Y, and Z. The respective boiling points in degrees Celsius are as follows:

- Hydrocarbon W: -23.0°C
- Hydrocarbon X: -103.7°C
- Hydrocarbon Y: -75.0°C
- Hydrocarbon Z: -47.0°C

We need to identify the hydrocarbon that is most likely an alkyne. Generally, alkynes have lower boiling points compared to alkenes of similar size due to the linear structure of alkynes, which leads to lesser intermolecular forces.

To determine which hydrocarbon is the alkyne, we should identify the one with the lowest boiling point among the given hydrocarbons. This is because the lower boiling point indicates weaker intermolecular forces, which is a characteristic feature of alkynes in comparison to alkenes of similar molecular size.

Let’s compare the boiling points:

- W: -23.0°C
- X: -103.7°C (Lowest boiling point)
- Y: -75.0°C
- Z: -47.0°C

The hydrocarbon with the lowest boiling point is X with a boiling point of -103.7°C. Therefore, it is most likely that hydrocarbon X is the alkyne.

Thus, the hydrocarbon that is most likely an alkyne is:

X

This conclusion is reached based on the observation of the boiling points provided and the chemical property that alkynes tend to have lower boiling points than alkenes of comparable size.

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