Freezing point of water is 0°C. At what temperature will one molal solution of NaCl freeze if NaCl is taken to be completely dissociated (molal depression constant of water = 1.86)?

• -3.72°C

• -1.86°C

• 0°C

• 3.72°C

52.

Structure of NaCl crystal is

• tetragonal

• cubic

• orthorhombic

• monoclinic

Bravais lattices are of

• 8 types

• 12 types

• 14 types

• 9 types

Point defects are present in

• ionic solids

• molecular solids

• amorphous solids

• liquids

The half-life of a radioactive element is 30min, one sixteenth of original quantity of element will remain unchanged after

• 1 h

• 16 h

• 4 h

• 2 h

If the amount of radioactive substance is increased three times, the number of atoms disintegrated per unit time would

• be double

• be triple

• remain one third

• not change

Half-life of a radioactive element is 100yr. The time in which it disintegrates to 50% of its mass, will be

• 50 yr

• 200 yr

• 100 yr

• 25 yr

120 gm urea is present in 5 L solution, the active mass of urea is

• 0.2

• 0.06

• 0.4

• 0.08

The term (dc/ dt)in a rate equation refers to the

• concentration of the reactant

• decreases in concentration of the reactant with time

• increase in concentration of the reactant with time

• velocity constant of the reaction

If the rate expression for a chemical reaction is given by rate = k[A]^m[B]ⁿ

• the order of the reaction is m

• the order of the reaction is n

• the order of the reaction is m + n

• the order of the reaction is m- n