Asubstance that undergoes a change in a chemical reaction is
a. a product.
c. a reactant.
b. a chemical.
d. an enzyme.

Option c. A substance that undergoes a change in a chemical reaction is a reactant.

Explanation:

In chemistry, a reactant is defined as a substance that takes part or undergoes a change during a chemical reaction in order to make a product. Some chemical reactions go to completion, which means that all reactants participating in that reaction become products. These type of chemical reactions are called irreversible. Other reactions do not go into completion, and there is a balance between the amount of reactants and products left, these reactions are called reversible.

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .

> b takes place in the gas phase in an isothermal tubular reactor. the feed is one mole of a per one mole of c, an inert. the entering temperature and pressure are 427°c and 10 atm, respectively. the gas constant r = 0.08206 atm · l/mol · k.