PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions for Chemistry

Following reactions occur at cathode during the electrolysis of aqueous sodium chloride solution:

Na+(aq) + e⁻ ⟶ Na (s) E⁰ =  2.71 V

H+(aq) + e⁻ ⟶ `1/2`  H₂ (g) E⁰ = 0.00 V

On the basis of their standard reduction electrode potential (E⁰) values, which reaction is feasible at the cathode and why?

Reduction of metal oxide to metal becomes easier if the metal obtained is in liquid state. Why?

[NiCl₄]²⁻ is paramagnetic, while [Ni(CO)₄] is diamagnetic, though both are tetrahedral. Why? (Atomic number of Ni = 28)

It is necessary to remove CO when ammonia is prepared by Haber's process.

Predict the products of the following reactions :

The presence of nitro group (−NO₂) at o/p positions increases the reactivity of haloarenes towards nucleophilic substitution reactions.

Account for the following : There is large difference between the melting and boiling points of oxygen and sulphur.

Give a simple chemical test to distinguish between the following pair of compounds :

(CH₃)₂NH and (CH₃)₃N

Write the dispersed phase and dispersion medium of butter.

Give reasons for the following : H₂Te is the strongest reducing agent amongst all the hydrides of Group 16 elements.

Give a simple chemical test to distinguish between the following pair of compounds :

CH₃CH₂CHO and CH₃CH₂COCH₃

What is the role of zinc metal in the extraction of silver ?

Give reasons for the following : Oxygen has less electron gain enthalpy with negative sign than sulphur.

Propanal and Propanone

Out of CH₃CH₂ – CO – CH₂ – CH₃ and CH₃CH₂ – CH₂ – CO – CH₃, which gives iodoform test?

What role does the molecular interaction play in a solution of alcohol and water?

How is the sign of Δ_mixH related to positive deviations from Raoult’s law?

Heptane and octane form an ideal solution. At 373 K, the vapour pressures of the two liquid components are 105.2 kPa and 46.8 kPa respectively. What will be the vapour pressure of a mixture of 26.0 g of heptane and 35 g of octane?

Suggest the most important type of intermolecular attractive interaction in the following pair.

acetonitrile (CH₃CN) and acetone (C₃H₆O)

Vapour pressure of pure acetone and chloroform at 328 K are 741.8 mm Hg and 632.8 mm Hg respectively. Assuming that they form ideal solution over the entire range of composition, plot `p_"total"`, `p_"chloroform"` and `p_"acetone"` as a function of `chi_"acetone"`. The experimental data observed for different compositions of mixtures is:

Plot this data also on the same graph paper. Indicate whether it has a positive  or negative deviation from the ideal solution.