Question

Use the normal boiling points: propane, C3H8, –42.1˚C; butane, C4H10, –0.5˚C; pentane, C5H12, 36.1˚C; hexane, C6H14, 68.7˚C; heptane, C7H16, 98.4˚C; to estimate the normal boiling point of octane, C8H18. Explain.

Answer 1

Answer:

The answer to your question is 126.1°C

Explanation:

                  Boiling point         Difference of boiling points  

C₃H₈             - 42.1°C

C₄H₁₀             -   0.5°C                 41.6 °C

C₅H₁₂               36.1°C                  36.6°C                       41.6 - 36.6 = 5°C          

C₆H₁₄               68.7°C                 32.6°C                        36.6 - 32.6 =4°C

C₇H₁₆               98.4°C                 29.7°C                        32.6 - 29.7 = 2.9°C

We can observe on the table that the difference of boiling points diminishes 1°C when the hydrocarbon has one more carbon, then the difference of temperature between the hydrocarbon of 8 carbons and the hydrocarbon of 7 carbons must be 2°C.

So, this difference is 29.7°C - 2°C = 27.7°C.

And the boiling point of octane is approximately 98.4 + 27.7°C = 126.1°C