HELP PLS!! WILL GIVE BRAINLIEST What is a catalyst? A a substance that slows a reaction down without being used up itself in a reaction. B a substance that is used up while speeding up a reaction. C a reactant that is added to speed up a reaction. D a substance that increases the rate of a reaction without being used up itself in a reaction.

D a substance that increases the rate of a reaction without being used up itself in a reaction.

Explanation:

Examples are

ammonia synthesis ==>iron

sulfuric acid manufacture==> nitrogen(II) oxide, platinum

cracking of petroleum==> zeolites

hydrogenation of unsaturated hydrocarbons ==>nickel, platinum, or palladium

I hope it helps

Hey there!

The correct answer would be D. "a substance that increases the rate of a reaction without being used up itself in a reaction."

Hope this helps :)

1. they vary with a higher number because boiling is way hotter than melting