Thermodynamics

Considering entropy(s) as a thermodynamic parameter, the criterion for the spontaneity of any process, the change in entropy is

• $∆{\mathrm{S}}_{\mathrm{system}} >0 \mathrm{only}$

• $∆{\mathrm{S}}_{\mathrm{surrounding}} > 0$

• $\left(∆{\mathrm{S}}_{\mathrm{system}} + ∆{\mathrm{S}}_{\mathrm{surrounding}}\right) > 0$

• $(∆{\mathrm{S}}_{\mathrm{system}} - ∆{\mathrm{S}}_{\mathrm{surrounding}}) > 0$

Standard enthalpy (heat) of formation of liquid water at 25°C is around

 H₂(g) + $\frac{1}{2}$O₂(g) → H₂O (l)

• -237 kJ/mol

• 237 kJ/mol

• - 286 kJ/mol

• 286 kJ/mol

Given ΔH_f° for CO₂(g) , CO(g) and H₂O(g) are -393.5, -110.5 and -241.8 kJ mol^-1, respectively. The ΔH_f° [in kJ mol^-1] for the reaction

CO₂(g) + H₂(g) → CO(g) + H₂O (g) is

• 524.1

• -262.5

• -417

• 412

For silver, C_P( K^-1 mol^-1) = 23 + 0.01T. If the temperature (T) of 3 moles of silver is raised from 300 K to 1000 K at 1 atm pressure, the value of $∆$H will be close to :

• 21 kJ

• 62 kJ

• 16 kJ

• 13 kJ

During compression of a spring the work done is 10 kJ and 2 kJ escaped to the surroundings as heat. The change in internal energy, $∆$U (in kJ) is:

• -12

• 8

• 12

• -8

Consider the given plot of enthalpy of the following reaction between A and B. A + B → C + D. Identify the incorrect statement.

• C is the thermodynamically stable product.

• Formation of A and B from C has highest enthalpy of activation.

• Activation enthalpy to form C is 5 kJ mol^-1 less than that to form D.

• D is kinetically stable product.

5 moles of an ideal gas at 100 K are allowed to undergo reversible compression till its temperature becomes 200 K. If CV = 28 J K–1 mol–1, calcuIate ΔU and ΔPV for this process. ( R= 8.0 JK^-1 mol^-1 )

• ΔU = 14kJ; Δ(pV) = 18kJ

• ΔU = 14kJ; Δ(pV) = 0.8J

• ΔU = 14kJ; Δ(pV) = 4kJ

• ΔU = 2.8kJ; Δ(pV) = o.8J

Among the following, the set of parameters that represents path functions, is:

(A) q+w

(B) q

(C) w

(D) H-TS

• A, B and C

• B, C and D

• B and C

• A and D

A process will be spontaneous at all temperatures if :

• ΔH <0 and ΔS <0

• ΔH <0 and ΔS >0

• ΔH >0 and ΔS >0

• ΔH >0 and ΔS <0

The standard Gibbs energy for the given cell reaction in kJ mol^-1 at 298 K is:

Zn (s) + Cu²⁺ (aq) → Zn²⁺ (aq) + Cu (s), E° = 2V at 298 K

• -192

• 384

• -384

• 192