Question

The volume of gas at NTP T = 293 K, V = 24 L is $1.12\times {10}^{-7}cc$. The number of molecule in it is

• A. $3.01\times {10}^{12}$
• B. $3.01\times {10}^{18}$
• C. $3.01\times {10}^{24}$
• D. $3.01\times {10}^{30}$

Answer 1

Answer: (A)

$3.01\times {10}^{12}$

NTP is commonly used as a standard condition for testing and documentation of fan capacities: NTP - Normal Temperature and Pressure - is defined as air at ${20}^{o}C$ ($293.15K$, ${68}^{o}F$) and 1 atm ($101.325kPa$) Density $1.204kg/m^3$ ($0.075$ pounds per cubic foot)

$\Rightarrow n=\frac{PV}{RT}=\frac{101325\times 1.12\times {10}^{-7}\times 0.000001}{8.314\times 273.15}=49.97\times {10}^{-13}$

For 1 mole $6.023\times {10}^{23}$

For $49.97\times 0.0000001$mole $49.97\times 0.0000001\times 0.000001\times 6.023\times {10}^{23}=3.01\times {10}^{12}$ molecules