Answers section

Questions 3.3.4

State the colour and physical state of ethyne.
Comment about the solubility of the gas in water. Explain your answer.
Show that the density of ethyne is less than of ethane gas (H = 1; C=12).
Explain why, like alkanes and alkenes, ethyne is soluble in organic compounds such as carbon tetrachloride.
How would you collect a dry sample of ethyne gas?

Answers to Questions 3.3.4

Ethyne is a colourless gas.
Ethyne is largely insoluble (only slightly soluble) in water, since it can be collected over water.
Relative molecular mass (RMM) of ethyne, CHCH, is 12+1+12+1 = 26. This is less than the RMM of ethane, CH₂CH₂, which is 12+2+12+2 = 28).
Because "likes dissolve likes" ethyne, being organic, is soluble in organic solvents.
Dry ethyne can be collected by upward delivery or downward displacement of air