Which increases the rate of a chemical reaction?
a. a catalyst
b. a higher volume
c. a lower pressure
d. a lower temperature user: how does a catalyst appear in a chemical equation?
a. it does not usually appear in an equation.
b. it only appears on the product side of an equation.
c. it only appears on the reactant side of an equation.
d. it appears on both the reactant and product sides of an equation.

Answers: 

1) Which increase the rate of a chemical reaction?

 [A]:  a catalyst .

Note:  A catalyst increases the rate of chemical reaction without altering the chemical reaction itself.

2) How does a catalyst appear in a chemical equation?

 [A]: it uses does usually appear in an equation.

Note: Since a catalyst is not used up or changed during the chemical reaction, catalysts usually do not appear in a chemical equation.
   {Occasionally, the catalyst is denoted above the "arrow" in the chemical equation, for emphasis that the catalyst was used."}.