Question

2. A student has two compounds in two separate bottles but with no labels on either one. One is an unbranched alkane, octane, CH1s; the other is 1-hexene, an unbranched alkene, C H,2- Based on your observations in this experiment, tell what you should see in the following tests: Octane 1-Hexene a. Water solubility b. Ligroin solubility Combustion c. d. Density versus water e. Bromine test f. Permanganate test

Answer 1

(a) Water Solubility

Both Octane and 1-Hexene are insoluble in water

(b) Ligroin Solubility

Ligroin is the petroleum consisting mostly of C₇ and C₈ hydrocarbons. It is used as a solvent. Since like dissolves like both Octane and 1-Hexene are soluble in Ligroin.

(c) Combustion

All hydrocarbons burn completely when exposed to sufficient oxygen. The complete combustion of octane proceeds as follows:

2C₈H₁₈ (l) + 25O₂ (g)  $\rightarrow$ 16CO₂ (g) + 18H₂O (g)

The complete combustion of 1-Hexene proceeds as follows:

C₆H₁₂(l) + 9O₂ (g)  $\rightarrow$ 6CO₂ (g) + 6H₂O (g)

(d) Density versus Water

Both Octane and 1-Hexene are less dense than water.

(e) Bromine Test

When an alkene is reacted with Bromine, double bond breaks and a bromine atom is attached to the alkene where the double bond is present. On the other hand, alkanes do not react with Bromine as double bond is not present in alkanes. Therefore, Octane does not react with Bromine whereas 1-Hexene reacts.

(f) Permanganate Test

Alkanes do not react with potassium permanganate whereas Alkenes do. Thus, 1-Hexene gives the Permanganate test while Octane does not.