31.

The correct order of solubility in water for He, Ne, Ar, Kr, Xe is :

• He > Ne > Ar > Kr > Xe

• Xe > Kr > Ar > Ne > He

• Ne > Ar > Kr > He > Xe

• Ar > Ne > He > Kr > Xe

Schottky defect defines imperfection in the lattice structure of a :

• solid

• gas

• liquid

• plasma

An AB₂ type structure is found in :

• NaCl

• CaF₂

• Al₂O₃

• N₂O

Which of the following does not have valence electron in 3d-subshell ?

• Fe (III)

• Cr (I)

• Mn (II)

• P (0)

Which of the following compound is a tribasic acid ?

• H₃PO₄

• H₃PO₂

• H₃PO₃

• H₄P₂O₇

Thermite is a mixture of iron oxide and :

• zinc powder

• potassium metal

• sodium shavings

• aluminium powder

An element (atomic mass 100 g/mol) having BCC structure has unit cell edge 400 pm. The density of element is (No. of atom in BCC (Z) = 2).

• 2.144 g/cm³

• 7.289 g/cm³

• 5.188 g/cm³

• 10.376 g/cm³

The size of colloidal particle is :

• 10^-3 to 10⁹ m

• 10^-9 to 10^-12 m

• 10^-6 to 10^-9 m

• 10^-12 to 10^-19 m

Assertion: Potassium and caesium are used in photoelectric cells.

Reason: Potassium and caesium emit electrons on exposure to light.

• If both assertion and reason are true and reason is a correct explanation of the assertion.

• If both the assertion and reason are true but the reason is not a correct explanation of the assertion.

• If the assertion is true but the reason is false.

• If both the assertion and reason are false.

Assertion: Physical absorption of molecules takes place on the surface only.
Reason: In this process, the bonds of the absorbed molecules are broken.

• If both assertion and reason are true and reason is a correct explanation of the assertion.

• If both the assertion and reason are true but the reason is not a correct explanation of the assertion.

• If the assertion is true but the reason is false.

• If both the assertion and reason are false.