Answer:
The amount of drug left in his body at 7:00 pm is 315.7 mg.
Explanation:
First, we need to find the amount of drug in the body at 90 min by using the exponential decay equation:

Where:
λ: is the decay constant = 
: is the half-life of the drug = 3.5 h
N(t): is the quantity of the drug at time t
N₀: is the initial quantity
After 90 min and before he takes the other 200 mg pill, we have:

Now, at 7:00 pm we have:

Therefore, the amount of drug left in his body at 7:00 pm is 315.7 mg (from an initial amount of 400 mg).
I hope it helps you!
Upper N upper H subscript 4 upper C l (s) right and left arrows stacked above each other upper N upper H subscript 3 (g) plus upper H upper C l (g)
Explanation:
The given equation is;
NH₄Cl ⇄ NH₃ + HCl
This equation is clearly different from the other ones.
- In the reactant going forward, there is a right and left arrows stacked above each other.
- The symbol is ⇄ and it is used to show reversibility of chemical reactions.
learn more:
Chemical reactions brainly.com/question/3953793
#learnwithBrainly
Isn't this a math problem?
If it is the the answer should be 102.
10 decimeters=1 meter
27x10=270
270-168=102
Answer: The blood circulatory system (cardiovascular system) delivers nutrients and oxygen to all cells in the body.
Explanation: