Answer: 6.38 moles of
are needed to react with 2.55 mol of 
Explanation:
The balanced chemical reaction for the combustion of ethyne is:

According to stoichiometry:
2 moles of
require = 5 moles of 
Thus 2.55 mol of
require =
moles of 
Thus 6.38 moles of
are needed to react with 2.55 mol of 
Answer:
ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
Explanation:
ccccccccccccccccccccccccccc
Sound waves need to travel through a medium such as a solid, liquid, or gas. The sound waves move through each of these mediums by vibrating the molecules in the matter. The molecules in solids are packed very tightly. Liquids are not packed as tightly as solids. And gases are very loosely packed. The spacing of the molecules enables sound to travel much faster through a solid than a gas. Sound travels about four times faster and farther in water than it does in air. This is why whales can communicate over huge distances in the oceans. Sound waves travel about thirteen times faster in wood than air. They also travel faster on hotter days as the molecules bump into each other more often than when it is cold.
Endothermic reaction is the answer.