In a first order reaction, the concentration of the reactant decrease from 0.6 M to 0.3 M in 15 min. The time taken for the concentration to change from 0.1 M to 0.025 M in minutes is

• 14

• 12

• 30

• 3

At 298 K the molar conductivities at infinite dilution (${\mathrm{\Lambda }}_{\mathrm{m}}^{°}$) of NH₄Cl, KOH and KCl are 152.8, 272.6 and 149.8 S cm² mol^-1respectively. The ${\mathrm{\Lambda }}_{\mathrm{m}}^{°}$ of NH₄OH in Scm² mol^-1 and % dissociation of 0.01 M NH₄OH with ${\mathrm{\Lambda }}_{\mathrm{m}}$= 25.1 S cm² mol^-1 at the same temperature are

• 275.6, 0.91

• 275.6, 91

• 266.6, 96

• 30, 84

23.

Vapour pressure in mm Hg of 0.1 mole of urea in 180 g of water at 25° C is (The vapour pressure of water at 25°C is 24 mm Hg)

• 2.376

• 20.76

• 23.76

• 24.76

The molar mass of a solute X in g mol^-1, if its 1% solution is isotonic with a 5% solution of cane sugar(molar mass = 342 g mol^-1), is

• 68.4

• 34.2

• 136.2

• 171.2

The structure of XeOF₄, is

• trigonal bipyramidal

• square pyramidal

• square planar

• pyramidal

The charring of sugar takes place when treated with concentrated H₂SO₄. What is the type of reaction involved in it?

• Dehydration reaction

• Hydrolysis reaction

• Addition reaction

• Disproportionation reaction

What is the role of limestone during the extraction of iron from haematite ore?

• Leaching agent

• Oxidising agent

• Reducing agent

• Flux

The oxidation state and covalency of Al in [AlCl(H₂O)₅]²⁺ are respectively

• +6,6

• +3,6

• +2,6

• +3,3

The increasing order of the atomic radius of Si, S, Na, Mg, Al is

• S < Si< Al< Mg< Na

• Na< Mg < Si< Al< S

• Na< Mg< Si< Al < S

• Na< Mg< Al< Si< S

The molecular interactions responsible for hydrogen bonding in  HF

• ion-induced dipole

• dipole-dipole

• dipole- induced dipole

• ion-dipole