NEET Class 12

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 Multiple Choice QuestionsShort Answer Type


Explain why aniline is not as basic as ammonia.

In aniline, the lone pair over nitrogen atom is in conjugation with the π-electrons of the benzene ring and it takes part in resonance. That is why availabiity of lone pair is not as that as in ammonia. Thus, aniline is less basic than ammonia.


How nitrobenzene is identified using Mulliken-Barker test?

Nitrobenzene is reduced using Zn and NH4Cl in alcohol medium.

The N-phenyl hydroxylamine when reacts with Tollen's reagent gives bright silver miror.


Why B2 is paramagnetic whereas C2 is dimagnetic?

For B2 (10e) the MO configuration is (σ1s)2 (σ*1s)2 (σ2s)2 (σ*2s)2 (π2px1 = π2py1)

Due to presence of unpaired electron π2px1 = π2py1 it shows paramagnetism.

C2(12e) the MO configuration is (σ1s)2 (σ*1s)2 (σ2s)2 (π2px2 = π2py2)

No unpaired electrons are there in C2 π2px2 = π2py2, hence it shows diamagnetism.


Explain briefly the cause of Lanthanoid contraction.

On moving in the lanthanoid series from left to right successive electrons enter into ante penultimate 4f-subshell which imparts very poor shielding effect (due to its diffused nature), hence effective nuclear charge gradually increases with increase in atomic number. That is why shrinkage is observed on moving through lanthanide series, this is known as lanthanide contraction.


Calculate the ratio of the rate of diffusion of oxygen to the rate of diffusion of hydrogen at constant temperature and pressure.

The ratio of the rate of diffusion of oxygen to the rate of diffusion of hydrogen at constant temperatre and pressure can be calculated as

r ∝ 1m

rO2rH2 = MH2MO2rO2rH2 = 232 = 14