If oxygen is present in `1 L` flask at a pressure of `7.6xx10^(-10) mm Hg` then the number of oxygen molecules in the flask at `0^(@) C` will be

Options

A. `0.27xx10^(10)`
B. `0.027xx10^(10)`
C. `2.7xx10^(10)`
D. `27xx10^(10)`

Answer

C

Explanation

Applying the ideal gas equation,
`pV = nRT`
or `n = (pV)/(RT) = (((7.6xx10^(-10)"mm Hg")/(760 "mm Hg atm"^(-1)))(1L))/(((0.0821L "atm")/(K mol))(273K))`
`= 0.000446xx10^(-10)` mol
`= 4.46xx10^(-14)`
Number of `O_(2)` molecules
`= ("Moles of" O_(2)) xx` (Avogadro's constant)
`= (4.46xx10^(-14) mol) (6.022xx10^(23) "molecules" mol^(-1))`
`= 26.8xx10^(9)`
`= 2.68xx10^(10)`
`= 2.7xx10^(10)`