At constant pressure and temperature, the direction of any chemical reaction is one where the...... decrease.

1. Entropy               

2. Enthalpy

3. Gibbs energy       

4. None of the above

The work done by a mass less piston in causing an expansion $∆$V (at constant temperature), when the opposing pressure, P is variable, is given by:

1. W= $-\int \mathrm{P}∆\mathrm{V}$               

2. W=0

3. W= -P$∆$V                     

4. none of these

Entropy decreases during:

1. crystallization of sucrose from solution

2. rusting of iron

3. melting of ice

4. vaporization of camphor

Entropy change of vaporization at constant pressure is given by:

1. $∆{\mathrm{S}}_{\mathit{(p}\mathit{)}}= \frac{∆{\mathrm{Hp}}_{}}{\mathrm{T}}$

2. $∆{\mathrm{S}}_{\mathit{\left(}v\mathit{\right)}}=\frac{∆{\mathrm{U}}_v}{\mathrm{T}}$

3. $∆{\mathrm{S}}_{\mathit{\left(}v\mathit{\right)}}= \frac{∆{\mathrm{H}}_v}{\mathrm{P}}$

4. None of the above

What is the entropy change for the reaction given below, 

2H₂ (g) + O₂ (g) $\to$2H₂O(l)

at temperature 300 K? Standard entropies of H₂ (g), O₂(g) and H₂O(l) are 126.6, 201.20 and 68.0 JK^-1mol^-1 respectively.

1. -318.4 JK^-1mol^-1                           .

2. 318.4 JK^-1mol^-1 

3. 31.84 JK^-1mol^-1                             

4. none of these

If S$°$ for H₂, Cl₂ and HCl are 0.13, 0.22 and 0.19 kJ K^-1mol^-1 respectively. The total change in standard entropy for the reaction, H₂ + Cl₂ $\to$2HCl is:

1. 30 J K^-1mol^-1                         

2. 40 J K^-1mol^-1

3. 60 J K^-1mol^-1                         

4. 20 J K^-1mol^-1

The direct conversion of A to B is difficult and thus it is converted by path A$\to$C$\to$D$\to$B. Given

$∆{\mathrm{S}}_{\mathrm{A}\to \mathrm{C}}=50 \mathrm{e}.\mathrm{u}; ∆{\mathrm{S}}_{\mathrm{C}\to \mathrm{D}}=30 \mathrm{e}.\mathrm{u}; ∆{\mathrm{S}}_{\mathrm{B}\to \mathrm{D}}=20 \mathrm{e}.\mathrm{u}.$

(Where e.u. is the entropy unit)
then $∆{\mathrm{S}}_{\mathrm{A}\to \mathrm{B}}$ would be:

1. +60 e.u                                       

2. +100 e.u

3. -60 e.u                                       

4. -100 e.u

In a flask, colourless N₂O₄(g) is in equilibrium with brown coloured NO₂(g). At equilibrium when the flask is heated to 100$°$C, the brown colour deepens and on cooling it becomes less coloured. Which statement is incorrect about this observation?

1. The $∆$H for the reaction N₂O₄(g)$\rightleftharpoons$ 2NO₂(g) is +ve

2. Paramagnetism increases on heating

3. The $∆$H-$∆$U at 100$°$C is equal to 200 cal

4. Dimerisation is reduced on heating

Enthalpy of the reaction,

CH₄(g) + 1/2O₂(g) $\to$CH₃OH(l), is negative. If the enthalpy of combustion of CH₄ and CH₃OH are x and y respectively, then
which relation is correct?                                 

1. x>y         

2. x<y         

3. x=y           

4. x$⩾$y

In the reaction, $∆$H and $∆$S both are positive. The condition under which the reaction would not be spontaneous is -

1. $∆$H>T$∆$S                             

2. $∆$S=$∆$H/T

3. $∆$H=T$∆$S                               

4. All of the above