Rate Constant k has UNITS! 

Zero Order Reactions
rate = k[A]0
 M/t = k
 k units:  M/s, M/min, M/hr, etc.

First Order Reactions
rate = k[A]
 M/t = k M
 k units: s-1, min-1, hr-1, etc.

Second Order Reactions
rate = k[A]2      rate = k[A][B]
 M/t = k M2
 k units: M-1s-1, M-1min-1, M-1hr-1, etc.

Third Order Reactions
rate = k[A]3      rate = k[A]2[B]     rate = k[A][B][C]
 M/t = k M3
 k units: M-2s-1, M-2min-1, M-2hr-1, etc.

n Order Reactions
rate = k[A]n
 M/t = k Mn
 k units: M-(n-1)s-1, etc.

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