10 questions from 2023
The number of endothermic processes from the following is ______.
A. \( \mathrm{I_2(g) \rightarrow 2I(g)} \)
B. \( \mathrm{HCl(g) \rightarrow H(g) + Cl(g)} \)
C. \( \mathrm{H_2O(l) \rightarrow H_2O(g)} \)
D. \( \mathrm{C(s) + O_2(g) \rightarrow CO_2(g)} \)
E. Dissolution of ammonium chloride in water
\( \mathrm{A_2} + \mathrm{B_2} \rightarrow 2\mathrm{AB} \). \( \Delta H^{0}_f = -200 \, \text{kJ mol}^{-1} \)
AB, \( \mathrm{A_2} \) and \( \mathrm{B_2} \) are diatomic molecules. If the bond enthalpies of \( \mathrm{A_2} \), \( \mathrm{B_2} \) and AB are in the ratio \( 1 : 0.5 : 1 \), then the bond enthalpy of \( \mathrm{A_2} \) is _____ \( \text{kJ mol}^{-1} \). (Nearest integer)
The enthalpy change for the conversion of \( \frac{1}{2}\text{Cl}_{2}(g) \) to \( \text{Cl}^{-}(aq) \) is \( ( - ) \) _____ \( \text{kJ mol}^{-1} \) (nearest integer):
Given: \( \Delta_{\text{dis}} H^{\theta}_{\text{Cl}_{2}(g)} = 240 \, \text{kJ mol}^{-1} \), \( \Delta_{\text{eg}} H^{\theta}_{\text{Cl}(g)} = -350 \, \text{kJ mol}^{-1} \), \( \Delta_{\text{hyd}} H^{\theta}_{\text{Cl}^{-}(g)} = -380 \, \text{kJ mol}^{-1} \)
In an ice crystal, each water molecule is hydrogen bonded to \( \_ \_ \_ \_ \) neighbouring molecules.
\( 28.0 \, \text{L} \) of \( \text{CO}_2 \) is produced on complete combustion of \( 16.8 \, \text{L} \) gaseous mixture of ethene and methane at \( 25^\circ \text{C} \) and \( 1 \, \text{atm} \). Heat evolved during the combustion process is ______ \( \text{kJ} \).
Given: \( \Delta H_c (\text{CH}_4) = -900 \, \text{kJ mol}^{-1} \)
\( \Delta H_c (\text{C}_2\text{H}_4) = -1400 \, \text{kJ mol}^{-1} \)
Given:
(A) \( 2\mathrm{CO(g)} + \mathrm{O_2(g)} \rightarrow 2\mathrm{CO_2(g)} \) \( \Delta H_1^{\ominus} = -x \, \text{kJ mol}^{-1} \)
(B) \( \mathrm{C(graphite)} + \mathrm{O_2(g)} \rightarrow \mathrm{CO_2(g)} \) \( \Delta H_2^{\ominus} = -y \, \text{kJ mol}^{-1} \)
The \( \Delta H^{\ominus} \) for the reaction
\( \mathrm{C(graphite)} + \dfrac{1}{2}\mathrm{O_2(g)} \rightarrow \mathrm{CO(g)} \) is:
\( 0.3 \, \mathrm{g} \) of ethane undergoes combustion at \( 27^\circ \mathrm{C} \) in a bomb calorimeter. The temperature of calorimeter system (including the water) is found to rise by \( 0.5^\circ \mathrm{C} \). The heat evolved during combustion of ethane of constant pressure is \( \_\_\_\_\_ \, \mathrm{kJ\,mol^{-1}} \). [Nearest integer]
(Given: The heat capacity of the calorimeter system is \( 20 \, \mathrm{kJ\,K^{-1}} \), \( R = 8.3 \, \mathrm{J\,K^{-1}\,mol^{-1}} \). Assume ideal gas behavior. Atomic mass of \( \mathrm{C} \) and \( \mathrm{H} \) are \( 12 \) and \( 1 \, \mathrm{g\,mol^{-1}} \) respectively).
Enthalpies of formation of \( \mathrm{CCl_4(g)} \), \( \mathrm{H_2O(g)} \), \( \mathrm{CO_2(g)} \) and \( \mathrm{HCl(g)} \) are \( -105 \), \( -242 \), \( -394 \) and \( -92 \, \text{kJ mol}^{-1} \) respectively. The magnitude of enthalpy of the reaction given below is ______ \( \text{kJ mol}^{-1} \). (Nearest integer)
\( \mathrm{CCl_4(g)} + 2\mathrm{H_2O(g)} \rightarrow \mathrm{CO_2(g)} + 4\mathrm{HCl(g)} \)
Solid fuel used in rocket is a mixture of \( \text{Fe}_2\text{O}_3 \) and Al (in ratio \( 1:2 \)). The heat evolved (\( \text{kJ} \)) per gram of the mixture is ______ (Nearest integer)
Given: \( \Delta H_f^\ominus(\text{Al}_2\text{O}_3) = -1700 \, \text{kJ mol}^{-1} \)
\( \Delta H_f^\ominus(\text{Fe}_2\text{O}_3) = -840 \, \text{kJ mol}^{-1} \)
Molar mass of Fe, Al and O are \( 56 \), \( 27 \) and \( 16 \, \text{g mol}^{-1} \) respectively.
At \( 25^\circ\mathrm{C} \), the enthalpy of the following processes are given:
\( \mathrm{H_2(g) + O_2(g) \rightarrow 2OH(g)} \quad \Delta H^\circ = 78\,\mathrm{kJ\,mol^{-1}} \)
\( \mathrm{H_2(g) + \tfrac{1}{2}O_2(g) \rightarrow H_2O(g)} \quad \Delta H^\circ = -242\,\mathrm{kJ\,mol^{-1}} \)
\( \mathrm{H_2(g) \rightarrow 2H(g)} \quad \Delta H^\circ = 436\,\mathrm{kJ\,mol^{-1}} \)
\( \mathrm{\tfrac{1}{2}O_2(g) \rightarrow O(g)} \quad \Delta H^\circ = 249\,\mathrm{kJ\,mol^{-1}} \)
What would be the value of \( X \) for the following reaction?________. (Nearest integer)
\( \mathrm{H_2O(g) \rightarrow H(g) + OH(g)} \quad \Delta H^\circ = X\,\mathrm{kJ\,mol^{-1}} \)
