Reaction rates

Mg (s) + 2 HCl (a q) \to MgCl_{2} (a q) + H_{2} (g)

The reaction between

Mg (s)

and

HCl (a q)

is represented by the equation above. In a kinetics experiment, a

0.080 g

sample of

Mg (s)

ribbon is added to an Erlenmeyer flask containing

50 mL

3.0 M HCl (a q)

25 ° C

. The rate of the reaction is determined by measuring the volume of

H_{2} (g)

produced every five seconds.

Which of the following experimental changes is most likely to decrease the rate of $H_{2} (g)$ ‍ production?

(Choice A)
Using a $0.080 g$ ‍ sample of powdered $Mg (s)$ ‍ instead of $Mg (s)$ ‍ ribbon
(Choice B)
Using $25 mL$ ‍ of $3.0 M HCl (a q)$ ‍ solution instead of $50 mL$ ‍
(Choice C)
Using a $1.5 M$ ‍ solution of $HCl (a q)$ ‍ instead of a $3.0 M$ ‍ solution
(Choice D)
Heating the $HCl (a q)$ ‍ solution to $30 ° C$ ‍ before adding the $Mg (s)$ ‍

AP®︎/College Chemistry