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NEET Chemistry Solved Question Paper 2008

Multiple Choice Questions

31.
Which one of the following arrangement does not give the correct picture of the trends indicated against it?

F₂ > Cl₂ > Br₂ > I₂ : Oxidising power

F₂ > Cl₂ > Br₂ > I₂ : Electron gain enthalpy

F₂ > Cl₂ > Br₂ > I₂ : Bond dissociation energy

F₂ > Cl₂ > Br₂ > I₂ : Bond dissociation energy

F₂ > Cl₂ > Br₂ > I₂ : Bond dissociation energy

Generally, bond dissociation energies decrease in a group. Bond dissociation energy also decreases with repulsion.

X-X Bond	F-F	Cl-Cl	Br- Br	I-I
Bond length (A)	1.42	1.99	2.28	2.67
Bond dissociation energy (kcal/mol)	38	57	45.5	35.6

In general, the bond dissociation energy decreases as the bond length increases, but the bond dissociation energy of F₂ is less than that of Cl₂. It is due to greater interelectronic repulsion between the lone pair of electrons on the two bonded fluorine atoms. Hence, the order of bond dissociation energy is as:

Cl₂ > Br₂ > F₂ > I₂

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32.

Standard free energies of formation (in kJ/mol) at 298 K are -237.2, 394.4 and -8.2 for H₂O (l), CO₂ (g) and pentane (g), respectively. The value of E_cell^o for pentane-oxygen fuel cell is

1.968 V
2.0968 V
1.0968 V
1.0968 V

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33.

Which of the following statements is not correct?

The fraction of the total volume occupied by the atoms in a primitive cell is 0.48
molecules solids are generally volatile
the number of carbon atoms in a unit cell
the number of carbon atoms in a unit cell

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34.

If 'a' stands for the edge length of the cubic system:simple cubic , body centred cubic and face centred cubic, then the ratio of radii of the spheres in these systems will be repsectively,

$1 half a semicolon space fraction numerator square root of 3 over denominator 4 end fraction a colon space fraction numerator 1 over denominator square root of 2 end fraction a$
$1 half a space colon space square root of 3 space a space colon thin space fraction numerator 1 over denominator square root of 2 end fraction straight a$
$1 half a space colon thin space fraction numerator square root of 3 over denominator 2 end fraction straight a space colon space fraction numerator square root of 2 over denominator 2 end fraction straight a$
$1 half a space colon thin space fraction numerator square root of 3 over denominator 2 end fraction straight a space colon space fraction numerator square root of 2 over denominator 2 end fraction straight a$

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35.

The rate constant k₁ and k₂ for two different reactions are 10¹⁶. e^-2000/T and 10¹⁵.e^-1000/T respectively. The temperature at which k₁ = k₂

1000 K
2000/2.303 K
2000 K
2000 K

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36.

How many stereoisomers does this molecule have?

$CH subscript 3 CH space equals space CHCH subscript 2 straight C asterisk times HBrCH subscript 3$

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37.

Percentage of free space in a body centred cubic unit cell is

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38.

With which one of the following elements silicon should be doped so as to give p - type of semiconductor?

Germanium
Arsenic
Selenium
Selenium

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39.

The bromination of acetone cytosine and guanine solution is represented by this equation.
CH₃COCH₃ (aq) + Br₂ (aq) →CH₃COCH₂Br (aq) + H⁺ (aq) + Br^- (aq)
These kinetic data were obtained for given reaction concentrations.