A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at 20$°$C are 440 mm of Hg for pentane and 120 mm of Hg for hexane. The mole fraction of pentane in the vapour phase would be

• 0.549

• 0.200

• 0. 786

• 0.478

292.

If for a sucrose solution, elevation in boiling point is 0.1°C, then what will be the boiling point of NaCl solution for same molal concentration ?

• 0.1$°$C

• 0.2$°$C

• 0.08$°$C

• 0.01$°$C

The vapour pressure of pure water is 25.0 mm Hg and that of an aqueous dilute solution of urea in 20mm Hg at 25°C. The molarity of the solution is:

• 12.6

• 14.9

• 13.8

• 9.6

The significant figures in 1.0024, 1.240 and 0.0020 are respectively

• 5, 4, 2

• 3, 3, 1

• 5, 3, 4

• 5, 3, 2

A cylinder of compressed gas contains nitrogen and oxygen in the ratio of 3:1 by mole. The total mass of the gas mixture if the cylinder is known to contain 2.5 x 10⁴ g of oxygen will be:

• 8 x 10³ g

• 9 x 10⁴ g

• 9 x 10³ g

• 8 x 10² g

Forty millilitre of CO was mixed 100 mL of O₂ and the mixture was exploded. On cooling, the reaction mixture was shaken with KOH. What volume of gas is left?

• 80 ml of O₂

• 60 ml of O₂

• 80 ml of CO₂

• 50 ml of CO₂

Arrange the following (I to IV) in the order of increasing masses:

I. 0.5 mole of O₃

II. 0.5 g atom of oxygen

III. 3.011 x 10²³ mlecules of O₂

IV. 5.6 l of CO₂ at STP

• II < IV < III < I

• IV < III < I < II

• II < I < IV < III

• I < II < III < IV

75 c.c. of N/5 H₂SO₄, 10 c.c. of N/2 HCl and 30 c.c. of N/10 HNO₃ are mixed together. The strength of the resulting acid mixture is:

• 0.1N

• 0.2N

• 0.3N

• 0.4N

One mole of FeC₂O₄ is oxidised by x moles of Cr₂${\mathrm{O}}_7^{2-}$ in acidic medium , x is:

• 0.5

• 1.0

• 1.5

• 2.0

One gram of mass is equal to :

• 9 x 10²⁰ ergs

• 7 x 10¹⁵ ergs

• 5 x 10¹⁰ ergs

• 3 x 10⁵ ergs