Number of molecules: What is the number of molecules `11.2 L` of nitrogen dioxide gas `(NO_(2))` at `NTP`
Strategy: First find the number of molecules using Avagadro's constant.

Explanation

step 1: According to Eq.(1.9), we have
Number fo moles fo `NO_(2) = ("volume of" NO_(2) "(liters) at NTP")/("Standard molar volume")`
`= (11.2 L)/(22.4 L mol^(-1)) = 0.5 mol NO_(2)`
step 2 : According to Eq.(1.8) we have
Number of `NO_(2)` molecules
= (Number of moles of `NO_(2)) xx` (Avagadro's constant)
`(0.5 mol NO_(2)) (6.022xx10^(23) (NO_(2) "molecule")/("Moles of" NO_(2)))`
`= 3.0xx10^(23) NO_(2)` molecules