A doctor orders 4.0 mL of phenobarbital elixir. If the phenobarbital is available as 30 mg per 7.5 mL, how many milligrams is given to the patient? Express your answer to two and include the appropriate units

Answer 1

To find the number of milligrams given to the patient, we need to find the amount of phenobarbital in 4.0 mL of the elixir.

First, let's find the concentration of phenobarbital in the elixir:
30 mg per 7.5 mL

To find the concentration of phenobarbital per mL, we divide both the numerator and denominator by 7.5:
30 mg / 7.5 mL = 4 mg / 1 mL

Therefore, the concentration of phenobarbital in the elixir is 4 mg/mL.

Next, we multiply the concentration by the volume of the elixir given to the patient:
4 mg/mL * 4.0 mL = 16 mg

So, 16 milligrams is given to the patient.