## 7B.1 mass of drug left in body

$\frac{d[R]}{dt}=-k[R]; \ln [R]=-kt + \ln [R]_{0}; t_{\frac{1}{2}}=\frac{0.693}{k}$

Hannah_1G
Posts: 100
Joined: Wed Sep 18, 2019 12:22 am

### 7B.1 mass of drug left in body

Does the initial mass of the drug replace the concentration in the rate law equation for solving for the left over mass? $[A]_{t}= [A]_{0}e^{-k_{r}t}$
Would I use this equation in 7B.1 to solve for how much drug is left?

Chris Tai 1B
Posts: 102
Joined: Sat Aug 24, 2019 12:16 am

### Re: 7B.1 mass of drug left in body

Yes, the initial mass of the drug replaces the initial concentration in the rate law equation that you've provided. So, you could use this equation in 7B.1 to solve for how much drug (mass) is leftover. This will get you the correct answer.