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!
Answer:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p²
Explanation:
This atom will likely have 4 electron shells denotation of – 2.8.8.4
Orbitals shells show the probability, in space around the nucleus, where to find an electron. It is important to note that the 3rd shell has an additional d orbital (-in addition to s and p). However, because the d orbital has a higher energy state than the 4s and 4p orbitals, the d orbital only fills up when these latter ones are completely filled. In this case, the 4p does not completely fill (hence we don't see the d orbital in the notation).
Answer:
When a substance is heated ,the kinetic energy of its molecules also increase.
Explanation:
K.E is directly proportional to T
The buoyancy of an object is dictated by its density. So let us calculate for density, where:density = mass / volume
Calculate the volume first of a solid cube:volume = (6 cm)^3 = 216 cm^3 = 216 mL
Therefore density is:density = 270 g / 216 mLdensity = 1.25 g / mL
Therefore this object will float in the layer in which the density is more than 1.25 g / mL.