The substance that increases the speed of a chemical reaction is called?

The correct answer is Catalyst.

Key Points

CONCEPT:

• Inhibitor: An inhibitor is a substance that slows down or retard a chemical reaction.Example: Acetanilide slows down the decomposition of hydrogen peroxide.  2H₂O₂  →  2H₂O + O₂
• Promoter:   A promoter is a substance which added with a catalyst to increase its activity or selectivity. Example: Traces of molybdenum is used as a promoter in the Haber process(formation of ammonia) to increase the catalytic activity of iron
• Moderator: Moderators are used in nuclear reactors to slow down the fast-moving neutrons. Example: Graphite, heavy water(D₂O).

EXPLANATION:

• ​A catalyst is a substance added to a chemical reaction to increase its rate.

Example:

1) Finely divided iron is used as a catalyst in the formation of ammonia(Haber process)

 N₂(g) + 3H₂(g)   ⇔  2NH₃(g)

2) Vanadium pentoxide (V₂O₅) is used as a catalyst in the combination of sulphur dioxide and oxygen to form sulphur trioxide

 2SO₂(g) + O₂(g)  ⇔  2SO₃(g)