Multiple Choice QuestionsWhich is the most thermodynamically stable form of carbon?
Carbon black
Graphene
Graphite
Diamond
The second ionisation enthalpies of Li, Be, B and C are in order
Li > B > C > Be
Li > C > B > Be
Be > C > B > Li
B > C > Be > Li
A.
Li > B > C > Be
The ionisation enthalpy depend on the following factors.
(i) Half-filled or fully filled atomic orbitals are more stable than other incomplete orbitals.
(ii) Smaller the size of atom/ion, more is the ionisation energy (IE) For 2nd IE all elements have M+ configuraton.
| Total no.of electrons | Outermost configuration | |
| Li+(Z=3) | 2 | 1s2 (fully filled) |
| Be+(Z=4) | 3 | 2s1(has more size than carbon) |
| B+(Z=5) | 4 | 2s2 (full filled) |
| C+(Z=6) | 5 | 2s22p1 (small size) |
Hence, correct order for 2nd IE is Li+>B+>C+ >Be+ or Li > B > C > Be.
The first four ionisation enthalpy values of an element are 191 kcal mol-1 578 kcal mol-1 872 kcal mol-1 and 5962 kcal mol-1 .The number of valence electrons in the element is
1
2
3
4
Among the following alkenes, which one is ,the most stable?
CH2=CH2
CH3-CH=CH2
CH3-CH=CH-CH3
(CH3)2C=C(CH3)2
For a fuel cell, which statementis correct?
Hydrogen is oxidised to H2O at cathode
Oxygen is reduced to OH- at anode
Hydrogen is oxidised to H2O at anode
Hydrogen is oxidised to H+ at anode
2 × 10-5C charge on Zn2+ ions corresponds to
2 × 10-5 mol of Zn2+ ions
6.22 × 107 Zn2+ ions
0.64 mg of Zn2+ ions
1 × 10-10 mol Zn2+ ions.
Which statement is true?
The adsorption of H2 by platinum black is known as sorption
The adsorption of H2 by charcoal is known as occlusion
The adsorption of H2 by platinum black is known as occlusion
The absorption of H2 by charcoal is known as chemisorption.
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