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CBSE - Class 11 Chemistry Thermodynamics Worksheet

1.
Calculate the standard enthalpy of formation of $CH_3OH(l)$ from the following data:
$CH_3OH (l) + \frac{3}{2} O_2(g) \rightarrow CO_2(g) + 2H_2O(l)$ ; $Δ_rH^o = -726 \text{ kJ mol}^{-1}$
$C(graphite) + O_2(g) \rightarrow CO_2(g)$ ; $Δ_cH^o = -393 \text{ kJ mol}^{-1}$
$H_2(g) + \frac{1}{2} O_2(g) \rightarrow H_2O(l)$; $Δ_fH^o = -286 \text{ kJ mol}^{-1}$.
2.
$ΔU^o$ 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. $= 0$
3.
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
$Δ_aH^o (Cl_2) = 242 \text{ kJ mol}^{-1}$
4.
The enthalpies of all elements in their standard states are:
a. unity b. zero c. < 0 d. different for each element
5.
Comment on the thermodynamic stability of $NO(g)$, given
$\frac{1}{2} N_2(g) + \frac{1}{2}O_2(g) \rightarrow NO(g)$; $Δ_rH^o = 90 \text{ kJ mol}^{-1}$
$NO(g) + \frac{1}{2}O_2(g) \rightarrow NO_2(g)$: $Δ_rH^o= -74 \text{ kJ mol}^{-1}$
6.
Enthalpy of combustion of carbon to $CO_2$ is $-393.5 \text{ kJ mol}^{-1}$. Calculate the heat released upon formation of 35.2 g of $CO_2$ from carbon and dioxygen gas.
7.
Enthalpies of formation of $CO(g)$, $CO_2(g)$, $N_2O(g)$ and $N_2O_4(g)$ are $-110$, $-393$, 81 and $9.7 \text{ kJ mol}^{-1}$ respectively. Find the value of $Δ_rH$ for the reaction:
$N_2O_4(g) + 3CO(g) \rightarrow N_2O(g) + 3CO_2(g)$
8.
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 $24 \text{ J mol}^{-1} K^{-1}$.
9.
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 $0^\circ C$.
$C_p [H_2O(l)] = 75.3 \text{ J mol}^{-1} K^{-1}$
$C_p [H_2O(s)] = 36.8 \text{ J mol}^{-1} K^{-1}$
10.
Calculate the entropy change in surroundings when 1.00 mol of $H_2O(l)$ is formed under standard conditions. $Δ_fH^o = -286 \text{ kJ mol}^{-1}$.
11.
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
12.
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?
13.
For the reaction,
$2 Cl(g) \rightarrow Cl_2(g)$, what are the signs of $ΔH$ and $ΔS$ ?
14.
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. $+52.26 \text{ kJ mol}^{-1}$
15.
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.
16.
The equilibrium constant for a reaction is 10. What will be the value of $ΔG^o$ ? $R = 8.314 \text{ JK}^{-1} \text{ mol}^{-1}$, $T = 300 K$.
17.
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.
18.
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.
19.
For the process to occur under adiabatic conditions, the correct condition is:
a. $?T = 0$ b. $?p = 0$ c. $q = 0$ d. $w = 0$
20.
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.
$NH_2CN(g) + \frac{3}{2}O_2(g) \rightarrow N_2(g) + CO_2(g) + H_2O(l)$

Worksheet Answers

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