21.

Which of the statements is not true?

• On passing H₂S through acidified K₂Cr₂O₇ solution, milky colour is observed.

• Na₂Cr₂O₇ is preferred over K₂Cr₂O₇ in volumetric analysis

• Na₂Cr₂O₇ solution in acidic medium is orange

• K₂Cr₂O₇ solution becomes yellow on increasing the pH beyond 7

Which nomenclature is not according to IUPAC system?

Sulphur trioxide can be obtained by which of the following reaction

Aluminium is extracted from alumina (Al₂O₃) by electrolysis of a molten mixture of 

• Al₂O₃ +HF +NaAlF₄

• Al₂O₃ + CaF₂ +NaAlF₄

• Al₂O₃ +Na₃AlF₆ +CaF₂

• Al₂O₃ +KF +Na₃AlF₆

In a reaction, A+B → Product, rate is doubled when the concentration of B is doubled, and rate increases by a factor of 8 when the concentrations of both the reactants (A and B) are doubled. Rate law for the reaction can be written as

• Rate = k[A][B]²

• Rate = k[A]²[B]²

• Rate = k[A][B]

• Rate k[A]²[B]

Which one of the following is a mineral of iron?

• Malachite

• Cassiterite

• Pyrolusite

• Magnetite

In Freundlich adsorption isotherm, the value of 1/n is

• between 0 and 1 in all cases

• between 2 and 4 in all cases

• 1 in case of physical adsorption

• 1 in case of chemisorption

A metal crystallises with a face-centered cubic lattice. The edge of the unit cell is 408 pm. The diameter of the metal atom is

• 288 pm

• 408 pm

• 144 pm

• 204 pm

In a zero order reaction for every 10^o rise of temperature, the rate is doubled. If the temperature is increased from 10^oC to 100^oC, the rate of the reaction will become

• 256 times

• 512

• 64 times

• 128 times

The number of octahedral voids (s) per atom present in a cubic close-packed structure is 

• 1

• 3

• 2

• 4