Answer : The limiting reagent is 
Solution : Given,
Moles of methane = 2.8 moles
Moles of
= 5 moles
Now we have to calculate the limiting and excess reagent.
The balanced chemical reaction is,

From the balanced reaction we conclude that
As, 2 mole of
react with 1 mole of 
So, 5 moles of
react with
moles of 
From this we conclude that,
is an excess reagent because the given moles are greater than the required moles and
is a limiting reagent and it limits the formation of product.
Hence, the limiting reagent is 
Ethyne also known as Acetylene and is the simplest Alkyne belonging to Unsaturated Hydrocarbons. It contains triple bond between two carbon atoms in a molecule. Carbon atoms in Acetylene are sp Hybridized and has a linear shape with bond angle of 180° is present between C-C-H bonds. This compound is also called as Binary Compound because it is made up of two elements i.e. Carbon and Hydrogen. The terminal Hydrogen in Acetylene is slightly Acidic in nature, and this compound can donate terminal proton to any strong base. These compounds generally give Electrophillic Addition Reactions.