$∆$H_fusion of a substance is 'x' and $∆$H_vap is 'y', then $∆$H_sublimation will be

• x + y

• x - y

• x/y

• y/x

$∆{\mathrm{S}}_{\mathrm{surr}}$ for an exothermic reaction is

• always positive

• always negative

• zero

• may be positive or negative

The vapour pressure of pure benzene at a certain temperature is 0.850 bar. A non-volatile, non-electrolyte solid weighing 0.5 g is added to 39.0 g of benzene (molar mass 78 g/mol). The vapour pressure of the solution then is 0.845 bar. What is the molecular mass of the solid substance?

• 58

• 180

• 170

• 145

Which statement is true for ferrocene?

• All Fe-C are of equal length.

• C are sp² hybridized.

• It was the first discovered organometallic compound.

• All of these

Assertion : C- O bond in metal carbonyl is long.

Reason : There is delocalisation of electrons from filled d orbitals into the empty orbitals on the CO ligands.

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

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

• If assertion is true but reason is false

• If both assertion and reason are false.

Assertion : F is more electronegative than Cl.

Reason : F has high electron affinity than Cl.

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

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

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion : Acetylene on reacting with sodamide gives sodium acetylidc and ammonia.

Reason : sp hybridised carbon atoms.

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

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

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion : As a salt such as NaCl dissolves, the Na⁺ and Cl^- ions leaving the crystal lattice acquire far greater freedom.

Reason : In thermodyanamic terms, the formation of solution occurs with a favourable change in free energy, i.e., $∆$H has a high positive value and T$∆$S a low negative value.

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

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

• If assertion is true but reason is false.

• If both assertion and reason are false.

19.

Assertion : Molecular nitrogen is less reactive than molecular oxygen.

Reason : The bond length of N₂ is shorter than that of oxygen.

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

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

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion : The equilibrium constant is fixed and a characteristic for any given chemical reaction at a specified temperature.

Reason : The composition of the final equilibrium mixture at a particular temperature depends upon the starting amount of reactants.

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

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

• If assertion is true but reason is false.

• If both assertion and reason are false.