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CBSE - Class 11 Chemistry Thermodynamics Worksheet

1.
Choose the correct answer. A thermodynamic state function is a quantity
a. used to determine heat changes b. whose value is independent of path c. used to determine pressure volume work d. whose value depends on temperature only.
2.
The enthalpy of combustion of methane, graphite and dihydrogen at 298 K are, $-890.3 \text{ kJ mol}^{-1}$, $-393.5 \text{ kJ mol}^{-1}$, and $-285.8 \text{ kJ mol}^{-1}$ respectively. Enthalpy of formation of $CH_4(g)$ will be
a. $-74.8 \text{ kJ mol}^{-1}$ b. $-52.27 \text{ kJ mol}^{-1}$ c. $+74.8 \text{ kJ mol}^{-1}$ d. $+52.26 \text{ kJ mol}^{-1}$
3.
A reaction, $A + B \rightarrow C + D + q$ is found to have a positive entropy change. The reaction will be
a. possible at high temperature b. possible only at low temperature c. not possible at any temperature d. possible at any temperature
4.
For the process to occur under adiabatic conditions, the correct condition is:
a. $?T = 0$ b. $?p = 0$ c. $q = 0$ d. $w = 0$
5.
In a process, 701 J of heat is absorbed by a system and 394 J of work is done by the system. What is the change in internal energy for the process?
6.
The enthalpies of all elements in their standard states are:
a. unity b. zero c. < 0 d. different for each element
7.
The reaction of cyanamide, $NH_2CN (s)$, with dioxygen was carried out in a bomb calorimeter, and $ΔU$ was found to be $-742.7 \text{ kJ mol}^{-1}$ at 298 K. Calculate enthalpy change for the reaction at 298 K.
$NH_2CN(g) + \frac{3}{2}O_2(g) \rightarrow N_2(g) + CO_2(g) + H_2O(l)$
8.
The equilibrium constant for a reaction is 10. What will be the value of $ΔG^o$ ? $R = 8.314 \text{ JK}^{-1} \text{ mol}^{-1}$, $T = 300 K$.
9.
For the reaction
$2 A(g) + B(g) \rightarrow 2D(g)$
$ΔU^o = -10.5 \text{ kJ}$ and $ΔS^o = -44.1 \text{ JK}^{-1}$.
Calculate $ΔG^o$ for the reaction, and predict whether the reaction may occur spontaneously.
10.
Given
$N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$; $Δ_rH^o = -92.4 \text{ kJ mol}^{-1}$
What is the standard enthalpy of formation of $NH_3$ gas?
11.
For the reaction,
$2 Cl(g) \rightarrow Cl_2(g)$, what are the signs of $ΔH$ and $ΔS$ ?
12.
Calculate the standard enthalpy of formation of $CH_3OH(l)$ from the following data:
$CH_3OH (l) + \frac{3}{2} O_2(g) \rightarrow CO_2(g) + 2H_2O(l)$ ; $Δ_rH^o = -726 \text{ kJ mol}^{-1}$
$C(graphite) + O_2(g) \rightarrow CO_2(g)$ ; $Δ_cH^o = -393 \text{ kJ mol}^{-1}$
$H_2(g) + \frac{1}{2} O_2(g) \rightarrow H_2O(l)$; $Δ_fH^o = -286 \text{ kJ mol}^{-1}$.
13.
For the reaction at 298 K,
$2A + B \rightarrow C$
$ΔH = 400 \text{ kJ mol}^{-1}$ and $ΔS = 0.2 \text{ kJ K}^{-1} \text{ mol}^{-1}$
At what temperature will the reaction become spontaneous considering $ΔH$ and $ΔS$ to be constant over the temperature range.
14.
Calculate the enthalpy change for the process
$CCl_4(g) \rightarrow C(g) + 4 Cl(g)$
and calculate bond enthalpy of C – Cl in $CCl_4(g)$.
$Δ_{vap}H^o(CCl_4) = 30.5 \text{ kJ mol}^{-1}$.
$Δ_fH^o (CCl_4) = -135.5 \text{ kJ mol}^{-1}$.
$Δ_aH^o (C) = 715.0 \text{ kJ mol}^{-1}$, where $Δ_aH^o$ is enthalpy of atomisation
$Δ_aH^o (Cl_2) = 242 \text{ kJ mol}^{-1}$
15.
For an isolated system, $ΔU = 0$, what will be $ΔS$ ?
16.
Calculate the number of kJ of heat necessary to raise the temperature of 60.0 g of aluminium from $35^\circ C$ to $55^\circ C$. Molar heat capacity of Al is $24 \text{ J mol}^{-1} K^{-1}$.
17.
Calculate the entropy change in surroundings when 1.00 mol of $H_2O(l)$ is formed under standard conditions. $Δ_fH^o = -286 \text{ kJ mol}^{-1}$.
18.
Comment on the thermodynamic stability of $NO(g)$, given
$\frac{1}{2} N_2(g) + \frac{1}{2}O_2(g) \rightarrow NO(g)$; $Δ_rH^o = 90 \text{ kJ mol}^{-1}$
$NO(g) + \frac{1}{2}O_2(g) \rightarrow NO_2(g)$: $Δ_rH^o= -74 \text{ kJ mol}^{-1}$
19.
$ΔU^o$ of combustion of methane is $-X \text{ kJ mol}^{-1}$. The value of $ΔH^o$ is
a. $= ?U^o$ b. > $?U^o$ c. < $?U^o$ d. $= 0$
20.
Calculate the enthalpy change on freezing of 1.0 mol of water at $10.0^\circ C$ to ice at $-10.0^\circ C$. $Δ_{fus}H = 6.03 \text{ kJ mol}^{-1}$ at $0^\circ C$.
$C_p [H_2O(l)] = 75.3 \text{ J mol}^{-1} K^{-1}$
$C_p [H_2O(s)] = 36.8 \text{ J mol}^{-1} K^{-1}$

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