Can I use mass instead of concentration in the rate law equation?

[haha1234]

Homework Statement

Homework Equations

ln[A]=-kt+ln[A]0

The Attempt at a Solution

In this equation,is it necessary to have [A] to be the concentration?
If there is the mass provided only,can I just subsitute [A]=mass?

Sorry for my poor english

 

[Borek]

It is about concentration. However, for a constant volume (and taking into account molar mass is constant for a given substance) you can be able to factor them out into k constant. That is just a simple math.