Thermodynamics

Which of the following is not correct?

• Dissolution of NH₄Cl in excess of water is an endothermic process.

• Neutralisation process is always exothermic

• The absolute value of enthalpy (H) can be determined experimentally.

• The heat of reaction at constant volume is denoted by ΔE.

Identify the reaction for which $∆\mathrm{H} \ne ∆\mathrm{E}$ :

• S(rhombic) + O₂ (g) → SO₂ (g)

• N₂ (g) + O₂ (g) → 2NO (g)

• H₂ (g) + Cl₂ (g) → 2HCl (g)

• CO (g) + $\frac{1}{2}$O₂ (g) → CO₂ (g)

Calculate enthalpy for formation of ethylene from the following data

$$\begin{gathered} \left(\mathrm{I}\right) {\mathrm{C}}_{\left(\mathrm{graphite}\right)} + {\mathrm{O}}_2\left(\mathrm{g}\right) \to {\mathrm{CO}}_2\left(\mathrm{g}\right); ∆\mathrm{H} = 393.5 \mathrm{kJ} \\ \left(\mathrm{II}\right) {\mathrm{H}}_2\left(\mathrm{g}\right) + \frac{1}{2}{\mathrm{O}}_2\left(\mathrm{g}\right) \to {\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right); ∆\mathrm{H} = -286.2 \mathrm{kJ} \\ \left(\mathrm{III}\right) {\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{g}\right) + 3{\mathrm{O}}_2\left(\mathrm{g}\right) \to 2{\mathrm{CO}}_2\left(\mathrm{g}\right) + 2{\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right): ∆\mathrm{H} = -1410.8 \mathrm{kJ} \end{gathered}$$

• 54.1 kJ

• 44.8 kJ

• 51.4 kJ

• 48.4kJ

A system is provided with 50 J of heat and the work done on the system is 10 J. What is the change in internal energy of the system in Joules?

• 60

• 40

• 50

• 10

Calculate $∆\mathrm{H}°$ for the reaction,

Na₂O (s) + SO₃ (g) → Na₂SO₄ (g) given the following-

(A) Na (s) + H₂O (l) → NaOH (s) + $\frac{1}{2}$H₂ (g) ; $∆$H° = -146 kJ

(B) Na₂SO₄ (s) + H₂O (l) → 2NaOH (s) + SO₃ (g) ; $∆\mathrm{H}°$ = +418 kJ

(C) 2Na₂O (s) + 2H₂ (g) → 4Na (s) + 2H₂O (l); $∆\mathrm{H}°$ = +259 kJ

• +823 kJ

• -581 kJ

• -435 kJ

• +531 kJ

C₆H₆ + O₃ → X $\stackrel{\mathrm{Zn}/ {\mathrm{H}}_2\mathrm{O}}{\to }$ Y; X and Y are respectively.

• diozonide, glycol

• triozonide, glyoxalic acid

• triozonide, glyoxal

• monoozonide, oxalic acid

What is the entropy change in JK^-1 during the melting of 27.3 g of ice at 0°C? (Latent heat of fusion of ice = 330 Jg^-1)

• 330

• 12.1

• 3.3

• 33

For which one of the following reactions, the entropy change is positive?

• H₂ (g) + $\frac{1}{2}$O₂ (g) → H₂O (l)

• Na⁺ (g) + Cl^- (g) → NaCl (s)

• NaCl (l) → NaCl (s)

• H₂O (l) → H₂O (g)

Molar heat capacity (C_p) of water at constant pressure is 75 JK^-1mol^-1. The increase in temperature (in K) of 100 g of water when 1 kJ of heat is supplied to it is

• 2.4

• 0.24

• 1.3

• 0.13

Calculate $∆\mathrm{G}°$ for the following cell reaction:

Zn (s) + Ag₂O (s) + H₂O (l) → Zn${}_{\mathrm{n}}^{2+}$ (aq) + 2Ag (s) + 2OH^- (aq)

E${}_{{\mathrm{Ag}}^{+}/ \mathrm{Ag}}^{°}$ = 0.80 V and E${}_{{\mathrm{Zn}}^{2+}/ \mathrm{Zn}}^{°}$ = -0.76 V

• -305 kJ/ mol

• -301 kJ/ mol

• 305 kJ/ mol

• 301 kJ/ mol