Answer:
[tex]2.8*10^{21}moleculesPH_{3}[/tex]
Explanation:
1. Convert from milimoles to moles:
[tex]4.75millimolesPH_{3}*\frac{0.001molPH_{3}}{1millimolPH_{3}}= 4.75*10^{-3}moles[/tex]
2. Use the Avogadro´s number to find the number of molecules in one mol:
[tex]4.75*10^{-3}molesPH_{3}*\frac{6.022*10x^{23}moleculesPH_{3}}{1molPH_{3}}=2.8*10^{21}moleculesPH_{3}[/tex]
