If a chemical change has taken place, which of these is most likely true?

original substance can be easily recovered.
composition of a substance is the same.
a completely new substance is formed.
an easily reversible process has taken place.

Option (c) is the correct answer.

Explanation:

A change in which there occurs a difference in chemical composition of a substance then it is known as chemical change.

For example, precipitation, reactivity, toxicity etc are chemical change.

In a chemical change, there will always be formation of a new compound or substance will take place.

For example, is a chemical change.

Thus, we can conclude that if a chemical change has taken place then a completely new substance is formed.

the equation that correctly represent the reaction for formation of ammonia is

n2+ 3h2 → 2nh3 (answer d)

1 mole of nitrogen gas (n2) react with 3 moles of hydrogen gas (h2) to form 2 moles of ammonia ( nh3). this is in a process known as haber process were iron is used as a catalyst and reaction take place that a higher temperature and pressure. the process is exothermic hence energy is released.