Question

question 22
1 point
there is typically a 0.15 mg dose of epinephrine in an epipen, how many molecules of epinephrine does that represent? given epinephrine is c₉h₁₃no₃ and has a molar mass of 183 g/mol.
a 4.9e17 molecules
b 9.0e19 molecules
c 2.5e - 25 molecules
d 4.9e20 molecules
e none of the above

Explanation:

Step1: Convert mass to grams

First, convert the mass of epinephrine from milligrams to grams. Given the mass is $0.15$ mg. Since $1$ mg = $10^{- 3}$ g, then $m = 0.15\times10^{-3}$ g.

Step2: Calculate the number of moles

Use the formula $n=\frac{m}{M}$, where $m$ is the mass and $M$ is the molar - mass. Here, $M = 183$ g/mol and $m=0.15\times 10^{-3}$ g. So $n=\frac{0.15\times 10^{-3}\text{ g}}{183\text{ g/mol}}=\frac{0.15}{183}\times10^{-3}\text{ mol}\approx8.19\times10^{-7}\text{ mol}$.

Step3: Calculate the number of molecules

Use Avogadro's number $N_A = 6.022\times10^{23}$ molecules/mol. The number of molecules $N=n\times N_A$. So $N=(8.19\times 10^{-7}\text{ mol})\times(6.022\times10^{23}\text{ molecules/mol})\approx4.9\times10^{17}$ molecules.

Answer:

A. 4.9E17 molecules