A sample of air contains only N2,O2 and H2O . It is saturated with water vapours and the total pressure is 640 torr. The vapour pressure of water is 40 torr and the molar ratio of N2:O2 is 3: 1. The partial pressure of N2 in the sample is

Question

A sample of air contains only N2,O2 and H2O . It is saturated with water vapours and the total pressure is 640 torr. The vapour pressure of water is 40 torr and the molar ratio of N2:O2 is 3: 1. The partial pressure of N2 in the sample is (A)  text480 torr (B)  text600 torr (C)  text525 torr (D)  text450 torr

Tardigrade Admin · Accepted Answer

Pressure of dry air =Pm o i s t a i r-Pw a t e r v a p o u r s=640-40=600torr. Partial pressure = mole fraction × PT ∴ Partial pressure of N2 and O2 are also in the ratio of 3: 1. Partial pressure of N2=(600 × 3/3 + 1)=450 torr .

Q. A sample of air contains only $N_{2}, O_{2}$ and $H_{2} O$ . It is saturated with water vapours and the total pressure is 640 torr. The vapour pressure of water is 40 torr and the molar ratio of $N_{2} : O_{2}$ is 3 : 1. The partial pressure of $N_{2}$ in the sample is

$480 torr$

$600 torr$

$525 torr$

$450 torr$

Pressure of dry air $= P_{m o i s t ai r} - P_{w a t er v a p o u rs} = 640 - 40 = 600 t orr .$
Partial pressure = mole fraction $\times P_{T}$
$∴$ Partial pressure of $N_{2}$ and $O_{2}$ are also in the ratio of 3 : 1.
Partial pressure of $N_{2} = \frac{600 \times 3}{3 + 1} = 450 t orr$ .

Q. A sample of air contains only N2​,O2​ and H2​O . It is saturated with water vapours and the total pressure is 640 torr. The vapour pressure of water is 40 torr and the molar ratio of N2​:O2​ is 3 : 1. The partial pressure of N2​ in the sample is

480 torr

600 torr

525 torr

450 torr