Waiting for answer This question has not been answered yet. You can hire a professional tutor to get the answer.

QUESTION

What are the units for k in first, second, and third order reactions?

The units for ##k## are ##"s"^(-1)##, ##"L·mol"^(-1)"s"^(-1)##, and ##"L"^2"mol"^(-2)"s"^(-1)##.

The units come from the rate laws

rate = ##k["A"]^n##, where ##n## is the order of the reaction. So

##k = "rate"/["A"]^n = (("mol·L"^-1)"s"^-1)/(("mol·L"^-1)^n) ##

##n## = 1: ##k = "rate"/(["A"]) = ("mol·L"^-1"s"^-1)/("mol·L"^-1) = "s"^-1##

##n## = 2: ##k = "rate"/(["A"]^2) = ("mol·L"^-1"s"^-1)/(("mol·L"^-1)^2) = "L·mol"⁻¹"s"^-1##

##n## = 3: ##k = "rate"/(["A"]^3) = ("mol·L"^-1"s"^-1)/("mol·L"^-1)^3 = "L"^2"mol"^-2"s"^-1##

In summary,

##k = "rate"/(["A"]^n) = ("mol·L"^-1"s"^-1)/(("mol·L"^-1)^n) = "L"^(n-1)"mol"^(1-n)"s"^-1##

The video below also shows you how to determine the units of the rate constant.

Show more
LEARN MORE EFFECTIVELY AND GET BETTER GRADES!
Ask a Question