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# NEET Chemistry Solved Question Paper 2007

#### Multiple Choice Questions

11.

Which among the following is the most stable carbocation?

• $\stackrel{+}{\mathrm{C}}{\mathrm{H}}_{3}$

• CH3$\stackrel{+}{\mathrm{C}}$H2

B.

The most stable carbocation is t-alkyl carbocation because the order of stability of alkyl carbocation is

t-alkyl > s-alkyl > p-alkyl > CH${}_{3}^{+}$ carbocation

This stability order is described with the help of hyperconjugation and inductive effect.

12.

Products of the following reaction

CH3$\equiv$C.CH2CH3 .... are

• CH3CHO + CH3CH2CHO

• CH3COOH + CH3COCH3

• CH3COOH + HOOC.CH2CH3

• CH3COOH + CO2

C.

CH3COOH + HOOC.CH2CH3

Product of the above given reaction is CH3COOH + HOOC.CH2CH3.

13.

Which one of the following oxides is expected to exhibit paramagnetic behaviour?

• CO2

• SO2

• ClO2

• SiO2

C.

ClO2

ClO2 shows paramagnetic character due to presence of unpaired electron in its structure.

14.

H2S gas when passed through a solution of cations containing HCl precipitates the cations of second group of qualitative analysis but not those belonging to the fourth group. It is because:

• presence of HCl decreases the sulphide ion concentration

• presence of HCl increases the sulphide ion concentration

• solubility product of group II sulphides is more than that of group IV sulphides

• sulphides of group IV cations are unstable in HCl

A.

presence of HCl decreases the sulphide ion concentration

H2S gas is passed in presence of HCl, in qualitative analysis of cation of second group, therefore, due to common ion effect, lower concentration of sulphide ions is obtained which is sufficient for the precipitation of second group cations in form of their sulphides due to lower value of their solubility product (Ksp). Here, fourth group cations are not precipitated because they require for exceeding their ionic product to their solubility products and higher sulphide ions concentration due to their higher Ksp which is not obtained here due to common ion effect.

# 15.Which of the following would have a permanent dipole moment?BF3 SiF3 SF4 XeF4

C.

SF4

Among all the given options, SF4 would have permanent dipole moment.

16.

Which one of the following is expected to exhibit optical isomerism? (en = ethylenediamine)

• cis-[Pt (NH3)2Cl2]

• trans-[Co (en)2 Cl2]

• trans- [Pt (NH3)2Cl2]

• cis-[Co(en)2Cl2]

B.

trans-[Co (en)2 Cl2]

Trans [CO (en)2Cl2] is able to exhibit the phenomena of optical isomerism because it can form a superimposable mirror image.

17.

Which one of the following compounds is most acidic?

• Cl - CH2 - CH2 - OH

B.

Phenols are much more acidic than alcohols, due to the stabilisation of phenoxide ion by resonance.

Phenoxide ion is stabilized due to following resonating structures :

Ortho nitrophenol is most acidic because in it -NO2 electron attracting group is attached on ortho position which helps in stabilising of negative charge on the oxygen of phenoxide ion.Hence, due to this reason acidic character of phenol is increased, while on attachment of -CH3 group (electron donating group) acidic strength of phenol is decreased in cresol due to destabilisation of phenoxide ion.

18.

A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at 20$°$C are 440 mm of Hg for pentane and 120 mm of Hg for hexane. The mole fraction of pentane in the vapour phase would be

• 0.549

• 0.200

• 0. 786

• 0.478

D.

0.478

Total vapour pressure of mixture

= (mole fraction of pentane x VP of pentane) + (mole fraction of hexane x VP of hexane)

= VP of pentane in mixture + VP of hexane in mixture

= 184 mm

Since,

VP of pentane in mixture = VP of mixture x mole fraction of pentane in vapour phase

88 = 184 x mole fraction of pentane in vapour phase

Therefore, Mole fraction of pentane in vapour phase = $\frac{88}{184}$ = 0.478

19.

Which one of the following alkenes will react faster with H2 under catalytic hydrogenation conditions?

(R = Alkyl substituent)

A.

Stability of alkene $\propto$

Greater the number of alkyl groups attached to the doubly bonded carbon atoms, more stable is the alkene. Hence, given alkene follow the following order of stability.

Hence, faster hydrogenation in

20.

4.5 g of aluminium (Atomic mass 27 amu) is deposited at cathode from Al3+ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from H+ ions in solution by the same quantity of electric charge will be

• 22.4 L

• 44.8 L

• 5.6 L

• 11.2 L

C.

5.6 L