Write the number of covalent bonds in the molecule of ethane.

What happens when (Give equations also):
$(i)$ Methane reacts with excess of chlorine in the presence of diffused sunlight.
$(ii)$ Ethanol undergoes combustion.
$(iii)$ Ethyl alcohol reacts with acidified potassium dichromate.

What happens when a small piece of sodium is dropped into ethanol?

Why are homologous series of carbon compounds so called? Write the chemical formula of two consecutive members of a homologous series and state the part of these compounds that determines their $(i)$ physical properties,and (ii) chemical properties.

Look at the figure and answer the following questions:
$(a)$ What change would you observe in the calcium hydroxide solution taken in tube $B$?
$(b)$ Write the chemical reactions involved in test tubes $A$ and $B$ respectively.

Draw the electron-dot structure for ethyne. $A$ mixture of ethyne and oxygen is burnt for welding. In your opinion,why cannot we use a mixture of ethyne and air for this purpose?