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Q:

The entropy change involved in the isothermal reversible expansion of 2 moles of an ideal gas from a volume of 10 $d m^{3}$ at 27°C is to a volume of 100 $d m^{3}$

A) 42.3 J/ mole / K	B) 38.3 J/ mole / K
C) 35.8 J/ mole / K	D) 32.3 J/ mole / K

Answer & Explanation Answer: B) 38.3 J/ mole / K

Explanation:

$∆ s = n R \ln \frac{v 2}{v 1}$

$= 2.303 n R \log \frac{v 2}{v 1}$ = $2.303 \times 2 \times 8.314 \times \log (\frac{100}{10})$ = $38.3 J$ $m o l^{- 1}$ $k^{- 1}$

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Q:

In a face centred cubic lattice, atom A occupies the corner positions and atom B occupies the face centre positions. If one atom of B is missing from one of the face centred points, the formula of the compound is

1) $A_{2} B_{5}$

2) $A_{3} B_{2}$

3) $A_{2} B_{3}$

4) $A_{3} B_{4}$

A) Option 1	B) Option 2
C) Option 3	D) Option 4

Answer & Explanation Answer: A) Option 1

Explanation:

$Z_{A} = \frac{8}{8}$ ; $Z_{B} = \frac{5}{2}$

So formula of compound is $A B_{\frac{5}{2}}$

i.e., $A_{2} B_{5}$ .

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Q:

The degree of dissociation ( $α$ ) of a weak electrolyte, $A_{x} B_{y}$ is related to van't Hoff factor (i) by the expression:

$1 . α = \frac{x + y + 1}{i - 1}$

$2 . α = \frac{x + y - 1}{i - 1}$

$3 . α = \frac{i - 1}{x + y + 1}$

$4 . α = \frac{i - 1}{x + y - 1}$

A) 1 is correct	B) 2 is correct
C) 3 is correct	D) 4 is correct

Answer & Explanation Answer: D) 4 is correct

Explanation:

Van't Hoff factor (i) = $\frac{O b s e r v e d C o l l i g a t i v e P r o p e r t y}{N o r m a l C o l l i g a t i v e P r o p e r t y}$

$\begin{matrix} A_{x} B_{y} \\ 1 - α \end{matrix} \to \begin{matrix} x A^{+ y} \\ x α \end{matrix} + \begin{matrix} y B^{- x} \\ y α \end{matrix}$

Total Moles = $1 - α + x α + y α$ = $1 - α (x + y - 1)$

$i = \frac{1 + α (x + y - 1)}{1}$

$\Rightarrow α = \frac{i - 1}{x + y - 1}$

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Q:

The structure of $I F^{7}$ is

A) Pentagonal bipyramid	B) Square pyramid
C) Trigonal bipyramid	D) Octahedral

Answer & Explanation Answer: A) Pentagonal bipyramid

Explanation:

Hybridisation of iodine is $s p^{3} d^{3}$

So, the structure is pentagonal bipyramid.

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Q:

The outer electron configuration of Gd (Atomic No : 64) is

1. $4 f^{7} 5 d^{1} 6 s^{2}$

2. $4 f^{3} 5 d^{5} 6 s^{2}$

3. $4 f^{8} 5 d^{0} 6 s^{2}$

4. $4 f^{4} 5 d^{4} 6 s^{2}$

Answer

Answer : 1

Sol :

1. $4 f^{7} 5 d^{1} 6 s^{2}$

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Q:

Ethylene glycol is used as an antifreeze in a cold climate. Mass of ethylene glycol which should be added to 4 kg of water to prevent it from freezing at –6°C will be: (Kf for water = 1.86 Kg/mol and molar mass of ethylene glycol = 62 kg/mol)

A) 204.60 g	B) 304.30 g
C) 804.32 g	D) 400.00 g

Answer & Explanation Answer: C) 804.32 g

Explanation:

$∆ T_{f} = k_{f} . m$

for ethylene glycol in aq. solution

$∆ T_{f} = k_{f} \frac{w}{m o l . w t} \times \frac{1000}{w t . o f s o l v e n t} 6 = \frac{1.86 x w x 1000}{62 x 4000}$

=> w = 800 g

So, the weight of solute should be more than 800 g.

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Q:

The magnetic moment (spin only) of $[N i C l_{4}]^{2 -}$ is

A) 1.41 BM	B) 1.82 BM
C) 5.46 BM	D) 2.82 BM

Answer & Explanation Answer: D) 2.82 BM

Explanation:

Hybridisation of Ni is $e^{-}$

Unpaired $3 d^{8}$ in is 2

So $Ω = \sqrt{n (n + 2)} B M = \sqrt{2 x 4} = \sqrt{8} = 2.82 B M$

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Q:

In a Certain Country 1/2 of 5 = 3. If the same proportion holds, what is the value of 1/3 of 10 ?

A) 4	B) 6
C) 8	D) 10

Answer & Explanation Answer: A) 4

Explanation:

Let $\frac{1}{3} (10) = x$

=> 3x = 10

Given that $\frac{1}{2} (5) = 3$

Therefore, $\frac{5}{2} x = 10$

=> x = 10/3 = 4.

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