# How many hydrogen atoms are in 5 molecules of isopropyl alcohol, C_3H_7O?

$40$
First, the correct chemical formula of isopropyl alcohol is ${C}_{3} {H}_{7} O H$ and not ${C}_{3} {H}_{7} O$.
That being said, ${C}_{3} {H}_{7} O H$ represents one molecule of isopropyl alcohol, which has $8$ Hydrogen atoms.
So, the number of Hydrogen atoms in 5 molecules of ${C}_{3} {H}_{7} O H$ will be $8 \times 5 = 40$.