Thermodynamics CBSE Questions & Answers

Thermodynamics

This is Chemistry Class 11 Thermodynamics CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

Comment on the thermodynamic stability of NO(g), given $\frac{1}{2}$N2 (g) +$\frac{{1}}{2}$ ${{\text{O}}_{\text{2}}}$ (g) $ \to $NO (g); ${\Delta _{\text{r}}}{{\text{H}}^0}$= 90 kJ ${\text{mol}} - {\text{1}}$ NO(g) +$\frac{1}{2}$ O2(g) $ \to {\text{ N}}{{\text{O}}_{\text{2}}}$ (g) : ${\Delta _{\text{r}}}{{\text{H}}^0}$= -74 kJ mol-1

A
${\text{N}}{{\text{O}}_{\text{2}}}$ (g) is unstable, but NO(g) is formed
B
${\text{N}}{{\text{O}}_{\text{2}}}$ (g) is stable, but NO(g) is formed
C
NO(g) is stable, but ${\text{N}}{{\text{O}}_{\text{2}}}$ (g) is formed
D
NO(g) is unstable, but ${\text{N}}{{\text{O}}_{\text{2}}}$ (g) is formed
Correct

Calculate the heat and the work associated with a process in which 5.00 mol of gas expands reversibly at constant temperature T = 298 K from a pressure of 10.00 to 1.00 atm

A
30.5 kJ, -28.5 kJ
B
25.5 kJ, -28.5 kJ
C
27.0 kJ, -28.5 kJ
D
28.5 kJ, -28.5 kJ
Correct

Thermodynamics is not concerned about

A
energy changes involved in a chemical reaction
B
the rate at which a reaction proceeds
Correct
C
the feasibility of a chemical reaction
D
the extent to which a chemical reaction proceeds

Which of the following statements is correct?

A
The presence of reacting species in a covered beaker is an example of open system
B
The presence of reactants in a closed vessel made up of copper is an example of a closed system.
Correct
C
The presence of reactants in a thermos flask or any other closed insulated vessel is an example of a closed system.
D
There is an exchange of energy as well as matter between the system and the surroundings in a closed system.

The state of a gas can be described by quoting the relationship between

A
amount, volume, temperature
B
temperature, amount, pressure
C
pressure, volume, temperature, amount
Correct
D
pressure, volume, temperature

The volume of gas is reduced to half from its original volume. The specific heat will be

A
increase four times
B
reduce to half
C
remain constant
Correct
D
be doubled

During complete combustion of one mole of butane, 2658 kJ of heat is released. The thermochemical reaction for above change is

A
$\begin{gathered} {C_4}{H_{10}}\left( g \right) + {O_2}\left( g \right) \to 4C{O_2}\left( g \right) + 5{H_2}O\left( l \right){\text{ }}{\Delta _c}H \hfill \\ = -2658.0{\text{ }}kJ\,mo{l^{-1}} \hfill \\ \end{gathered} $
Correct
B
$\begin{gathered} {C_4}{H_{10}}\left( g \right) + {O_2}\left( g \right) \to 4C{O_2}\left( g \right) + 5{H_2}O\left( l \right){\Delta _c}H \hfill \\ = + 2658.0{\text{ }}kJ{\text{ }}mo{l^{--1}} \hfill \\ \end{gathered} $
C
$\begin{gathered} {C_4}{H_{10}}\left( g \right) + {O_2}\left( g \right) \to 4C{O_2}\left( g \right) + 5{H_2}O\left( l \right){\Delta _c}H \hfill \\ = --1329.0{\text{ }}kJ{\text{ }}mo{l^{--1}} \hfill \\ \end{gathered} $
D
$\begin{gathered} 2{C_4}{H_{10}}\left( g \right) + 13{O_2}\left( g \right) \to 8C{O_2}\left( g \right) + 10{H_2}O\left( l \right){\Delta _c}H \hfill \\ = --2658.0{\text{ }}kJ{\text{ }}mo{l^{--1}} \hfill \\ \end{gathered} $

${\Delta _{\text{f}}}{{\text{U}}^0}$of formation of ${\text{C}}{{\text{H}}_{\text{4}}}$ (g) at certain temperature is –393 kJ ${\text{mo}}{{\text{l}}^{--{\text{1}}}}$. The value of ${\Delta _{\text{f}}}{{\text{H}}^0}$is

A
< ${\Delta _{\text{f}}}{{\text{U}}^0}$
Correct
B
zero
C
equal to ${\Delta _{\text{f}}}{{\text{U}}^0}$
D
> ${\Delta _{\text{f}}}{{\text{U}}^0}$

In an adiabatic process, no transfer of heat takes place between system and surroundings. Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following.

A
q = 0, $\Delta {\text{T}}$ = 0, w = 0
Correct
B
q $ \ne $ 0, $\Delta {\text{T}}$ = 0, w = 0
C
q = 0, $\Delta {\text{T}}$ < 0, w $ \ne $ 0
D
q = 0, $\Delta {\text{T }} \ne $0, w = 0

The pressure-volume work for an ideal gas can be calculated by using the expression w = −$\mathop \smallint \limits_{{V_i}}^{{V_f}} {p_{ex}}dV$. The work can also be calculated from the pV– plot by using the area under the curve within the specified limits. When an ideal gas is compressed (a) reversibly or (b) irreversibly from volume Vi to Vf . choose the correct option.

A
w (reversible) > w (irreversible)
B
w (reversible) = w (irreversible)
C
w (reversible) < w (irreversible)
Correct
D
w (reversible) = w (irreversible) + ${{\text{p}}_{{\text{ex}}}}.\Delta {\text{V}}$

The entropy change can be calculated by using the expression $\Delta {\text{S }} = $$\frac{{{q_{rev}}}}{T}$ When water freezes in a glass beaker, choose the correct statement amongst the following :

A
$\Delta {\text{S}}$ (system) decreases but $\Delta {\text{S}}$ (surroundings) increases
Correct
B
$\Delta {\text{S}}$ (system) decreases and $\Delta {\text{S}}$ (surroundings) also decreases
C
$\Delta {\text{S}}$ (system) increases but $\Delta {\text{S}}$ (surroundings) decreases
D
$\Delta {\text{S}}$ (system) decreases but $\Delta {\text{S}}$ (surroundings) remains the same

On the basis of thermochemical equations (a), (b) and (c), find out which of the algebraic relationships given in options (i) to (iv) is correct. (a) C (graphite) $ + {\text{ }}{{\text{O}}_{\text{2}}}\left( {\text{g}} \right){\text{ }} \to {\text{ C}}{{\text{O}}_{\text{2}}}\left( {\text{g}} \right){\text{ }};{\text{ }}{\Delta _{\text{r}}}{\text{H }} = {\text{ x kJ mo}}{{\text{l}}^{--{\text{1}}}}$ (b) C (graphite) +$\frac{1}{2}$ O2 (g) $ \to {\text{ CO }}\left( {\text{g}} \right){\text{ }};{\text{ }}{\Delta _{\text{r}}}{\text{H }} = {\text{ y kJ mo}}{{\text{l}}^{--{\text{1}}}}$ (c) CO (g) +$\frac{1}{2}$ O2 (g) $ \to {\text{ C}}{{\text{O}}_{\text{2}}}\left( {\text{g}} \right){\text{ }};{\text{ }}{\Delta _{\text{r}}}{\text{H }} = {\text{ z kJ mo}}{{\text{l}}^{--{\text{1}}}}$

A
z = x + y
B
x = y – z
C
y = 2z – x
D
x = y + z
Correct

Consider the reactions given below. On the basis of these reactions find out which of the algebric relations given in options (i) to (iv) is correct? (a) C (g) + 4 H (g) $ \to {\text{ C}}{{\text{H}}_{\text{4}}}\left( {\text{g}} \right);{\text{ }}{\Delta _{\text{r}}}{\text{H }} = {\text{ x kJ mo}}{{\text{l}}^{--{\text{1}}}}$ (b) C (graphite,s) + ${\text{2}}{{\text{H}}_{\text{2}}}\left( {\text{g}} \right){\text{ }} \to {\text{ C}}{{\text{H}}_{\text{4}}}\left( {\text{g}} \right);{\text{ }}{\Delta _{\text{r}}}{\text{H }} = {\text{ x kJ mo}}{{\text{l}}^{--{\text{1}}}}$

A
x = 2y
B
x < y
C
x > y
Correct
D
x = y

The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound

A
may be positive or negative
Correct
B
is never negative
C
is always positive
D
is always negative

Enthalpy of sublimation of a substance is equal to

A
enthalpy of fusion + enthalpy of vapourisation
Correct
B
enthalpy of vapourisation
C
enthalpy of fusion
D
twice the enthalpy of vapourisation