Thermodynamics

Consider the following reactions:


Enthalpy of formation of H₂O (l) is:

• - x₂ kJ mol^-1

• + x₃ kJ mol^-1

• - x₄ kJ mol^-1

• - x₄ kJ mol^-1

Given that bond energy of H-H and Cl- Cl are 430 kJ mol^-1 and 240 kJ mol^-1 respectively and ΔH_f for HCl is -90 kJ mol^-1. Bond and ΔH_f for HCl is -90 kJ mol^-1.Bond enthalpy of HCl is:

• 290 kJ mol^-1

• 380 kJ mol^-1

• 425 kJ mol^-1

• 425 kJ mol^-1

Assume each reaction is carried out in an open container. For which reaction will ΔH = ΔE?

• H₂ (g) + Br₂ (g) →2HBr (g)

• C (s) + 2 H₂O (g) → 2 H₂ (g) + CO₂ (g)

• PCl₅ (g) →PCl₃ (g) + Cl₂ (g) 

• PCl₅ (g) →PCl₃ (g) + Cl₂ (g) 

The enthalpy of combustion of H₂, cyclohexene (C₆H₁₀) and cyclohexene (C₆H₁₂) are -241, -3800 and -3920 kJ per mol respectively.The heat of hydrogenation of cyclohexane is:

• -212 kJ mol

• +121 kJ mol

• +242 kJ per mol

• +242 kJ per mol

A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy ΔU of the gas in joules will be

• 1136.5 J

• -500 J

• -505 J

• -505 J

For a given reaction, ΔH = 35.5 kJ mol^–1 and ΔS = 83.6 JK^–1 mol^–1. The reaction is spontaneous at (Assume that ΔH and ΔS do not vary with temperature)

• T < 425 K

• T > 425 K

• All temperatures

• All temperatures

Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below :

$Br{O}_4^{-} \stackrel{1.82}{\to }Br{O}_3^{-}\stackrel{1.5 V}{\to }HBrO\stackrel{1.595}{\to }B{r}_2\stackrel{1.0652 V}{\to }B{r}^{-}$

Then the species undergoing disproportionation is

• $Br{O}_3^{-}$

• $Br{O}_4^{-}$

• HBrO

• Br₂

Which one of the following conditions will favour maximum formation of the product in the reaction,

$$\begin{gathered} A_2 \left(g\right)\hspace{0.17em} + B_2 \left(g\right) \stackrel{ }{\leftrightharpoons } X_2 \left(g\right) \\ {∆}_r H = - XkJ? \end{gathered}$$

• Low temperature and high pressure

• Low temperature and low pressure

• High temperature and low pressure

• High temperature and high pressure

The bond dissociation energies of X₂, Y₂ and XY are in the ratio of 1 : 0.5: 1. ΔH for the formation of XY is –200 kJ mol–1. The bond dissociation energy of X₂ will be

• 200 kJ mol^-1

• 100 kJ mol^-1

• 400 kJ mol^-1

• 800 kJ mol^-1

The correction factor ‘a’ to the ideal gas equation corresponds to

• Density of the gas molecules

• Volume of the gas molecules

• Forces of attraction between the gas molecules

• Electric field present between the gas molecules