Class 11th

The entropy change can be calculated by using the expression ∆S = . When water freezes in a glass beaker, choose the correct statement amongst the following:

(i) ∆S (system) decreases, but ∆S (surroundings) remains the same.

(ii) ∆S (system) increases, but ∆S (surroundings) decreases.

(iii) ∆S (system) decreases, but ∆S (surroundings) increases.

(iv) ∆S (system) decreases, and ∆S (surroundings) also decreases.

Assertion (A): Nitration of benzene with nitric acid requires the use of concentrated sulphuric acid. 

Reason (R): The mixture of concentrated sulphuric acid and concentrated nitric acid produces the electrophile, NO₂ ⁺. 

(i) Both A and R are correct and R is the correct explanation of A. 

(ii) Both A and R are correct but R is not the correct explanation of A. 

(iii) Both A and R are not correct. 

(iv) A is not correct but R is correct.

The pressure volume work for an ideal gas can be calculated by using the expression w = - ${\int }_{{\mathit{V}}_{\mathit{i}}}^{{\mathbf{V}}_{\mathbf{f}}}{\mathit{P}}_{\mathit{e}\mathit{x}}$ dv. The work can also be calculated from the pV−plot by using the area under the curve within the specified limits. When an ideal gas is compressed (a) reversibly or (b) irreversibly from volume Vi to Vf. Choose the correct option.

(i) w (reversible) = w (irreversible)

(ii) w (reversible) < w (irreversible)

(iii) w (reversible) > w (irreversible)

(iv) w (reversible) = w (irreversible) + p_ex.?V

In an adiabatic process, no transfer of heat takes place between system and surroundings. Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following.

(i) q = 0, ∆T ≠ 0, w = 0

(ii) q ≠ 0, ∆T = 0, w = 0

(iii) q = 0, ∆T = 0, w = 0

(iv) q = 0, ∆T < 0, w 0 V_f

Assertion (A): Toluene on Friedal Crafts methylation gives o– and p–xylene. 

Reason (R): CH₃-group bonded to benzene ring increases electron density at o– and p– position. 

(i) Both A and R are correct and R is the correct explanation of A. 

(ii) Both A and R are correct but R is not the correct explanation of A. 

(iii) Both A and R are not correct. 

(iv) A is not correct but R is correct.

It is cyclic and has conjugated 8π-electron system but it is not an aromatic compound.

Reason (R) : (4n + 2) π electrons rule does not hold good and ring is not planar.

(i) Both A and R are correct and R is the correct explanation of A.

(ii) Both A and R are correct but R is not the correct explanation of A.

(iii) Both A and R are not correct.

(iv) A is not correct but R is correct.

Match the reactions given in Column I with the reaction types in Column II.

Match the following reactants in Column I with the corresponding reaction products in Column II.

∆_fU $°$ of formation of CH₄ (g) at certain temperature is –393 kJ/mol. The value of ∆_fH $°$ is

(i) zero

(ii) < _f U $°$

(iii) > ∆_f U $°$

(iv) Equal to ∆_fU $°$

Match the hydrocarbons in Column I with the boiling points given in Column II.