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# NEET Chemistry Solved Question Paper 2013

#### Multiple Choice Questions

1.

Total number of antibonding electrons present in O2 will be

• 6

• 8

• 4

• 2

A.

6

Total number of antibonding electrons present in O2 is 6.

2.

Maximum number of unpaired electrons are present in

• Gd3+

• Yb2+

• Tb2+

• Pm3+

A.

Gd3+

Maximum number of unpaired electrons are present in Gd3+. It has 7 unpaired electrons.

Yb2+ has no unpaired electrons.

Tb2+ has 5 unpaired electrons.

Pm3+ has 4 unpaired electrons.

3.

Which of the following is most basic?

• Al(OH)3

• Cr(OH)3

• La(OH)3

• Fe(OH)3

C.

La(OH)3

La(OH)3 is the most basic as it has the largest atomic size. Al(OH)3 is amphoteric in nature.

4.

K2Cr2O7 in acidic medium converts into

• Cr2+

• Cr3+

• Cr4+

• Cr5+

B.

Cr3+

K2Cr2O7 in acidic medium converts into Cr3+. Since it is an oxidising agent, it undergoes reduction, i.e. decrease in oxidation state.

Cr2O${}_{7}^{2-}$ + 14H+ + 6e- $\to$2Cr3+ + 7H2O

5.

In BF3, the B - F bond length is 1.30Å, when BF3 is allowed to be treated with Me3N, it forms an adduct, Me3N $\to$ BF3, the bond length of B - F in the adduct is

• greater than 1.30 Å

• smaller than 1.30 Å

• equal to 1.30 Å

• none of these

A.

greater than 1.30 Å

In BF3, there is back bonding in between fluorine and boron due to presence of p-orbital in boron. Back bonding imparts double bond characteristics.

As BF, forms adduct the back bonding is no longer present and thus double bond characteristic disappears. Hence, bond becomes a bit longer than earlier (1.30 Å).

6.

Assertion : Bond dissociation energy is F2 > Cl2.

Reason : Cl2 has more electronic repulsion than F2.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

D.

If both assertion and reason are false.

Bond dissociation energy is F2 < Cl2 because of relatively large electron-electron repulsion among the lone pairs in F2 molecule where they are much closer to each other
than in Cl2.

7.

What will be the solubility product of AX3?

• 27S4

• 4S3

• 36S4

• 9S3

A.

27S4

AX3 $⇌$

Ksp = [A3+] [X-]3

= (S).(3S)3 = 27S4

8.

A particle is moving 3 times faster than the speed of electron. If the ratio of wavelength of particle and electron is 1.8 x 10-4 then particle is

• neutron

• $\mathrm{\alpha }$- particle

• deuteron

• tritium

A.

neutron

Given : $\frac{{\mathrm{\lambda }}_{\mathrm{particle}}}{{\mathrm{\lambda }}_{\mathrm{electron}}}$ = 1.8 $×$ 10-4

and $\frac{{\mathrm{\nu }}_{\mathrm{particle}}}{{\mathrm{\nu }}_{\mathrm{electron}}}$ = 3

According to de-Brogile equation,

Actual mass of neutron is 1.67493 $×$ 10-27 kg. Hence, the particle is neutron.

9.

Which thermodynamic parameter is not a state function?

• q at constant pressure

• q at constant volume

• W at isothermal

D.

W at isothermal

and are state functions but W and q are not state functions.

From the equation,

At constant pressure,

At constant volume,

At constant pressure,

so, it is a state function.

At constant volume, $∆$V = 0, $∆$U = qv

so, it is a state function.

Work done in any adiabatic process is state function.

$∆$U = q - W ( $\because$ q = 0)

$∆$U = -W

Work done in isothermal process is not a state function.

W = -q ($\because$ $∆$T = 0, q $\ne$ 0)

10.

Which of the following element has lowest melting point?

• Cr

• Fe

• Ni

• Cu

D.

Cu

Cu has lowest melting point because it has lowest enthalpy of atomisation (i.e., heat required to break the metal lattice to get free atoms) among the elements.