Subject

Chemistry

Class

NEET Class 12

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NEET Chemistry Solved Question Paper 2007

Multiple Choice Questions

The heat of formarion of CO₂ is - 393 kJ mol^-1 .The amount of heat evolved in the formation of 0.156 kg of CO₂ .

- 1393 kJ
+ 1165.5 kJ
+ 1275.9 kJ
- 1165.5 kJ

- 1393 kJ

$∵$ Heat evolved during the formation of 44 g of CO₂ = - 93kJ

$∴$ Heat evolved in the formation of 0.156 kg of CO₂

= $\frac{- 393 \times 156}{44}$

= - 1393 kJ

Hess's law is based on :

law of conservation of mass
law of conservation of energy
enthalpy is a state function
none of the above

law of conservation of energy

Hess's law is based upon conservation of energy .

Heat of neutralisation of an acid with a base is 13. 7 kcal when :

both acid and base are weak
acid is weak and base is strong
both acid and base are strong
acid is strong and base is weak

both acid and base are strong

Heat of neutralisation for strong acid and strong base is always close to 13.7 kcal .

$\underset{strong acid}{HA}$ + $\underset{strong base}{BOH}$ $⇌$ H₂O + AB

$∆$ H = - 13.7 Kcal

The heat of neutralisation of strong acid and strong base is actually the heat of formation of 1 gmole of water from 1 g of H⁺ and 1 g of OH^- .

The solubility product of Mg(OH)₂ at 25°C is 1.4 x 10^-11 .What is the solubility of Mg(OH)₂ in g/L ?

0.0047 g/L
0.047 g/L
0.0087 g/L
0.087 g/L

0.0087 g/L

Mg(OH)₂ $⇌$ Mg²⁺ + 2OH^-

K_sp = [Mg²⁺][OH^-]²

1.4 X 10^-11 = (s)(2s)²

1.4 X 10^-11 = 4s³

s = 1.5 x 10^-4 mol/L

( $∵$ Mol. wt. of Mg(OH)₂ = 52)

= 58 X 1.5 x 10^-4

= 0.0087 g/L

What is the frequency of a X-ray photon whose momentum is 1.1 x 10^-23 kg-ms^-2?

5 x 10¹⁶ Hz
0.5 x 10²⁷ Hz
0.5 x 10¹⁸ Hz
5 x 10¹⁸ Hz

5 x 10¹⁸ Hz

E = mc²

E = hv

mc² = hv

$ν$ = $\frac{{mc}^{2}}{h}$ = $\frac{1.1 \times 10^{- 23} \times 3 \times 10^{8}}{6.6 \times 10^{- 34}}$

= 5 x 10¹⁸ Hz

The bond energy is the energy required to :

dissociate one mole of the substance
dissociate bond in 1 kg of the substance
break one mole of similar bonds
break bonds in one mole of the substance

break one mole of similar bonds

Bond energy : It may be defined as the energy released when two atoms get bonded or it is equal to the energy required to break the bond to form the neutral atoms .

e.g , H-H (g) $\to$ H + H , $∆$ H = + 103 Kcal/mol

The magnitude of orbital angular momentum of an electron of azimuthal quantum number 2 is :

$\frac{2 h}{2 π}$
$\frac{\sqrt{6} h}{2 π}$
$\frac{\sqrt{2} h}{2 π}$
$\frac{6 h}{2 π}$

$\frac{\sqrt{6} h}{2 π}$

Orbital angular momentum = $\sqrt{l (l + 1)}$ $\frac{h}{2 π}$

where l = azimuthal quantum number

$\frac{\sqrt{6} h}{2 π}$

The pH of a 0.02 M solution of HCl is :

1.7

0.02 M HCl = 2 x 10^-2 M HCl

[H⁺] = 2 x 10^-2

pH = - log[H⁺]

= - log [2 x 10^-2]

= - log 2 + 2 log 10

= - 0.3010 + 2

= 1.7

9.
Heisenberg's uncertainty principle can be explained as :

$∆$ x $⩾$ $\frac{∆ p \times h}{4 π}$

$∆$ x x $∆$ p $⩾$ $\frac{h}{4 π}$

$∆$ x x $∆$ p $⩾$ $\frac{h}{π}$

$∆$ p $⩾$ $\frac{πh}{∆ x}$

$∆$ x x $∆$ p $⩾$ $\frac{h}{4 π}$

Heisenberg's uncertainty principle : It is not possible to determine precisely both the position and the momentum (or velocity) of a small moving particle (e.g , electron , proton etc)

$∆$ x . $∆$ p $⩾$ $\frac{h}{4 π}$

where $∆$ x , $∆$ p are the uncertainties with regard to position , momentum respectively .