A gaseous mixture contains 56 g of N₂, 44 g of CO₂ and 16 g of CH₄. The total pressure of the mixture is 720 mm Hg. The partial pressure of CH₄ is-

1. 180 mm

2. 360 mm

3. 540 mm

4. 720 mm

In a flask of volume V litres, 0.2 mol of oxygen, 0.4 mol of nitrogen, 0.1 mol of ammonia and 0.3 mol of helium are enclosed at ${27}^{o}C$. If the total pressure exerted by these non-reacting gases is one atmosphere, the partial pressure exerted by nitrogen is-

1. 1 atm

2. 0.1 atm

3. 0.2 atm

4. 0.4 atm

Which among the following mixtures of gases at room temperature does not obey Dalton's law of partial pressure-

1. He and O₂

2. NH₃ and HCl

3. H₂ and He

4. N₂ and He