Thermodynamics Questions

In which of the following processes does entropy increase?(A) Liquid evaporating to vapor.(B) Lowering the temperature of a gas.(C) Decomposition of ${\text{NaHCO}}_3(s)$ to ${\text{Na}}_2{\text{CO}}_3(s)$, ${\text{CO}}_2(g)$, and ${\text{H}}_2\text{O}(g)$.(D) Dissociation of ${\text{Cl}}_2(g)$ into $2\text{Cl}(g)$.

The temperature of gas is $-50^{\circ }\text{C}$. To what temperature the gas should be heated so that the RMS speed is increased by $3$ times?

A refrigerator is

Match List I with List II:
| List I (Process) | List II (Conditions) |
| (A) Isothermal process | (I) No heat exchange |
| (B) Isochoric process | (II) Carried out at constant temperature |
| (C) Isobaric process | (III) Carried out at constant volume |
| (D) Adiabatic process | (IV) Carried out at constant pressure |

The work done during reversible isothermal expansion of one mole of hydrogen gas at $25^{\circ }\text{C}$ from a pressure of $20\text{atm}$ to $10\text{atm}$ is:(Given $R=2.0{\text{cal K}}^{-1}{\text{mol}}^{-1}$, $\ln 2\approx 0.693$)

Reversible expansion of an ideal gas under isothermal and adiabatic conditions are as shown in the figure (AB Isothermal, AC Adiabatic). Which of the following options is not correct?

$1\text{g}$ of water of volume $1{\text{cm}}^3$ at $100^{\circ }\text{C}$ is converted into steam at the same temperature under normal atmospheric pressure $\approx 1\times 10^5\text{Pa}$. The volume of steam formed equals $1671{\text{cm}}^3$. If the specific latent heat of vaporization of water is $2256\text{J/g}$, the change in internal energy is:

The following graph represents the $T-V$ curves of an ideal gas at three pressures $P_1,P_2$ and $P_3$.

Then the correct relation is:

A thermodynamic system is taken through the cycle $abcda$. The work done by the gas along the path $bc$ is:

An ideal gas expands isothermally from $10^{-3}{\text{m}}^3$ to $10^{-2}{\text{m}}^3$ at $300\text{K}$ against a constant pressure of $10^5{\text{Nm}}^{-2}$. The work done by the gas is:

Pure silicon at $0\text{K}$ behaves as a/an:

A gaseous mixture consists of $16\text{ g}$ of helium and $16\text{ g}$ of oxygen. The ratio $C_P/C_V$ of the mixture is:

For the reaction, $2Cl(g)\to C{l}_2(g)$, the correct option is:

The figure shows a system of two concentric spheres of radii $r_1$ and $r_2$ and kept at temperatures $T_1$ and $T_2$ respectively. The radial rate of flow of heat in a substance between the two concentric sphere is proportional to:

A reaction is spontaneous when:

A system goes from A to B via two processes I and II as shown in the figure. If $\Delta U_1$ and $\Delta U_2$ are the changes in internal energies in the processes I and II respectively, then:

The temperature-entropy diagram of a reversible engine cycle is given in the figure. Its efficiency is:

Which of the following is incorrect regarding the first law of thermodynamics?

"Heat cannot by itself flow from a body at lower temperature to a body at higher temperature" is a statement of consequence of:

According to Newton’s law of cooling, the rate of cooling of a body is proportional to $(\Delta \theta {)}^n$, where $\Delta \theta$ is the difference of the temperature of the body and the surroundings, and $n$ is equal to:

Value of universal gas constant, $R$, depends upon:

Two cylinders $A$ and $B$ of equal capacity are connected to each other via a stop cock. $A$ contains an ideal gas at standard temperature and pressure. $B$ is completely evacuated. The entire system is thermally insulated. The stop cock is suddenly opened. The process is:

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio $C_p/C_v$ for the gas is:

The SI unit of heat is

$\text{C(s)}+2{\text{H}}_2\text{(g)}\to {\text{CH}}_4\text{(g)};\Delta H=-74.8{\text{kJ mol}}^{-1}$. Which of the following diagrams gives an accurate representation of the above reaction? [$R\to$ reactants; $P\to$ products]

A container has two chambers of volumes $V_1=2\text{litres}$ and $V_2=3\text{litres}$ separated by a partition made of a thermal insulator. The chambers contains $n_1=5$ and $n_2=4$ moles of ideal gas at pressures $p_1=1\text{atm}$ and $p_2=2\text{atm}$, respectively. When the partition is removed, the mixture attains an equilibrium pressure of:

An oxygen cylinder of volume $30\text{litre}$ has $18.20\text{moles}$ of oxygen. After some oxygen is withdrawn from the cylinder, its gauge pressure drops to $11\text{atmospheric pressure}$ at temperature $27^{\circ }\text{C}$. The mass of the oxygen withdrawn from the cylinder is nearly equal to:[Given, $R=\frac{100}{12}{\text{J mol}}^{-1}{\text{K}}^{-1}$, molecular mass of ${\text{O}}_2=32$, $1\text{atm pressure}=1.01\times 10^5{\text{N/m}}^2$ ]

Two gases A and B are filled at the same pressure in separate cylinders with movable pistons of radius $r_A$ and $r_B$, respectively. On supplying an equal amount of heat to both the systems reversibly under constant pressure, the pistons of gas A and B are displaced by $16\text{cm}$ and $9\text{cm}$, respectively. If the change in their internal energy is the same, then the ratio $r_A/r_B$ is equal to:

An ideal gas heat engine operates in Carnot cycle between 227°C and 127°C. It absorbs 6 x 10^4 cal of heat at higher temperature. Amount of heat converted to work is :

Which of the following processes is reversible ?

The temperature of inversion of a thermocouple is 620°C and the neutral temperature is 300°C. what is the temperature of cold junction ?

When $1\text{kg}$ of ice at $0^{\circ }\text{C}$ melts to water at $0^{\circ }\text{C}$, the resulting change in its entropy, taking latent heat of ice to be $80\text{cal/g}$ is approximately:

During an isothermal expansion, a confined ideal gas does $-150\text{J}$ of work against its surrounding. This implies that:

Which of the following is correct option for free expansion of an ideal gas under adiabatic condition?

If the enthalpy change for the transition of liquid water to steam is $30{\text{kJ mol}}^{-1}$ at $27^{\circ }\text{C}$, the entropy change for the process would be:

If the $E_{cell}^{\circ }$ for a given reaction has a negative value, then which of the following gives the correct relationships for the values of $\Delta G^{\circ }$ and $K_{eq}$?

Enthalpy change for the reaction $2{\text{H}}_{(\text{g})}\to {\text{H}}_{2(\text{g})}$ is $-869.6\text{kJ}$. The dissociation energy of $\text{H}-\text{H}$ bond is:

In which of the following the hydration energy is higher than the lattice energy?

Consider the following reactions:(i) ${\text{H}}^{+}(aq)+{\text{OH}}^{-}(aq)={\text{H}}_2\text{O}(l)$, $\Delta H=-x_1{\text{ kJmol}}^{-1}$ (ii) ${\text{H}}_2(g)+\frac{1}{2}{\text{O}}_2(g)={\text{H}}_2\text{O}(l)$, $\Delta H=-x_2{\text{ kJmol}}^{-1}$ (iii) ${\text{CO}}_2(g)+{\text{H}}_2(g)=\text{CO}(g)+{\text{H}}_2\text{O}(l)$, $\Delta H=-x_3{\text{ kJmol}}^{-1}$ (iv) ${\text{C}}_2{\text{H}}_2(g)+\frac{5}{2}{\text{O}}_2(g)=2{\text{CO}}_2+{\text{H}}_2\text{O}(l)$, $\Delta H=-x_4{\text{ kJmol}}^{-1}$ The enthalpy of formation of ${\text{H}}_2\text{O}(l)$ is:

Given that bond energy of $\text{H—H}$ and $\text{Cl-Cl}$ is $430{\text{ kJ mol}}^{-1}$ and $240{\text{ kJ mol}}^{-1}$ respectively and $\Delta H_f$ for $\text{HCl}$ is $-90{\text{ kJ mol}}^{-1}$. The bond enthalpy of $\text{HCl}$ is:

An ideal gas is compressed to half its initial volume by means of several processes. Which of the process results in the maximum work done on the gas?

Standard entropies of $X_2,Y_2$ and $X{Y}_3$ are $60,40$ and $50{\text{JK}}^{-1}{\text{mol}}^{-1}$ respectively. For the reaction $\frac{1}{2}{X}_2+\frac{3}{2}{Y}_2\rightleftharpoons X{Y}_3,\Delta H=-30\text{kJ}$ to be at equilibrium, the temperature should be:

The value of coefficient of volume expansion of glycerin is $5\times 10^{-4}{\text{K}}^{-1}$. The fractional change in the density of glycerin for a rise of $40^{\circ }\text{C}$ in its temperature is:

The correct thermodynamic conditions for the spontaneous reaction at all temperatures is:

Assume each reaction is carried out in an open container. For which reaction will $\Delta H=\Delta E$ ?

For an endothermic reaction, energy of activation is $E_a$ and enthalpy of reaction is $\Delta H$ (both of these in $\text{kJ/mol}$). The minimum value of $E_a$ will be:

Consider the following liquid – vapour equilibrium: $\text{Liquid}\rightleftharpoons \text{Vapour}$. Which of the following relations is correct?

The molecules of a given mass of a gas have r.m.s velocity of $200{\text{ms}}^{-1}$ at $27^{\circ }\text{C}$ and $1.0\times 10^5{\text{Nm}}^{-2}$ pressure. When the temperature and pressure of the gas are respectively $127^{\circ }\text{C}$ and $0.05\times 10^5{\text{Nm}}^{-2}$, the r.m.s. velocity of its molecules in ${\text{ms}}^{-1}$ is:

A diatomic gas ($\gamma =1.4$) at $2\text{atm}$ is compressed adiabatically so temp rises from $27^{\circ }\text{C}$ to $927^{\circ }\text{C}$. Final pressure is:

A gas is compressed isothermally to half its initial volume. The same gas is compressed separately through an adiabatic process until its volume is again reduced to half. Then:

A refrigerator works between $4^{\circ }\text{C}$ and $30^{\circ }\text{C}$. It is required to remove $600\text{calories}$ of heat every second in order to keep the temperature of the refrigerated space constant. The power required is: (Take $1\text{cal}=4.2\text{Joules}$)

The enthalpy and entropy change for the reaction:${\text{Br}}_2(\text{l})+{\text{Cl}}_2(\text{g})\to 2\text{BrCl}(\text{g})$ Are $30{\text{kJ mol}}^{-1}$ and $105{\text{JK}}^{-1}{\text{mol}}^{-1}$ respectively. The temperature at which the reaction will be in equilibrium is:

Given:$(1)$ $A\to 2B,\Delta H=+150$$(2)$ $3B\to 2C+D,\Delta H=-125$$(3)$ $E+A\to 2D,\Delta H=+350$ For $B+D\to E+2C$, $\Delta H$ will be:

For a sample of perfect gas when its pressure is changed isothermally from $p_i$ to $p_f$, the entropy change is given by:

Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at $100^{\circ }\text{C}$, while the other one is at $0^{\circ }\text{C}$. If the two bodies are brought into contact, then assuming no heat loss, the final common temperature is:

A body cools from a temperature $3T$ to $2T$ in $10\text{minutes}$. The room temperature is $T$. Assume that Newton's law of cooling is applicable. The temperature of the body at the end of next $10\text{minutes}$ will be:

The enthalpy of combustion of ${\text{H}}_2$, cyclohexene (${\text{C}}_6{\text{H}}_{10}$) and cyclohexane (${\text{C}}_6{\text{H}}_{12}$) are -241, -3800 and -3920 kJ per mol respectively. Heat of hydrogenation of cyclohexene is :

One mole of an ideal monatomic gas undergoes a process described by the equation $P{V}^3=\text{constant}$. The heat capacity of the gas during this process is:

The temperature inside a refrigerator is $t_2^{\circ }\text{C}$ and the room temperature is $t_1^{\circ }\text{C}$. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be:

Assertion: Reversible systems are difficult to find in real world.Reason: Most processes are dissipative in nature.

A Carnot engine whose sink is at $300\text{K}$ has an efficiency of $40\%$. By how much should the temperature of the source be increased so as to increase its efficiency by $50\%$ of original efficiency?

A given sample of an ideal gas occupies a volume $V$ at a pressure $P$ and absolute temperature $T$. The mass of each molecule of the gas is $m$. Which of the following gives the density of the gas?

The molar specific heat at a constant pressure of an ideal gas is $(7/2)R$. The ratio of specific heat at constant pressure to that at constant volume is:

Assertion: Air quickly leaking out of a balloon becomes cooler.Reason: The leaking air undergoes adiabatic expansion.

Equal volumes of two monoatomic gases, $A$ and $B$, at same temperature and pressure are mixed. The ratio of specific heats ($C_p/C_v$) of the mixture will be:

An ideal gas goes from state $A$ to state $B$ via three different processes. If $Q_1,Q_2,Q_3$ indicate the heat absorbed and $\Delta U_1,\Delta U_2,\Delta U_3$ indicate the change in internal energy:

The enthalpy of fusion of water is $1.435\text{kcal/mol}$. The molar entropy change for the melting of ice at $0^{\circ }\text{C}$ is:

In which of the following reactions, standard reaction entropy change ($\Delta S^{\circ }$) is positive and standard Gibb’s energy change ($\Delta G^{\circ }$) decreases sharply with increasing temperature?

Assertion: In pressure-temperature ($P$ -$T$) phase diagram of water, the slope of the melting curve is found to be negative.Reason: Ice contracts on melting to water.

Standard enthalpy of vapourisation ${\Delta }_{\text{vap}}{H}^{\circ }$ for water at $100^{\circ }\text{C}$ is $40.66\text{kJ/mol}$. The internal energy of vapourisation of water at $100^{\circ }\text{C}$ (in $\text{kJ/mol}$) is:

One mole of an ideal gas goes from an initial state $A$ to final state $B$ via two processes: It first undergoes isothermal expansion from volume $V$ to $3V$ and then its volume is reduced from $3V$ to $V$ at constant pressure. The correct $P-V$ diagram representing the two processes is:

A thermodynamic system is taken through the cycle $ABCD$ as shown in figure. Heat rejected by the gas during the cycle is:

If $Q$, $E$, and $W$ denote respectively the heat added, change in internal energy, and the work done in a closed cycle process, then:

The molar specific heats of an ideal gas at constant pressure and volume are denoted by $C_p$ and $C_v$, respectively. If $\gamma =\frac{C_p}{C_v}$ and $R$ is the universal gas constant, then $C_v$ is equal to:

A gas is taken through the cycle $A\to B\to C\to A$, where $A=(2,2\times 10^5)$, $B=(2,6\times 10^5)$, and $C=(7,2\times 10^5)$ in $(V,P)$ coordinates ($V$ in $10^{-3}{\text{m}}^3$, $P$ in $\text{Pa}$). What is the net work done by the gas?

$\Delta H_f^{\circ }(298\text{K})$ of methanol is given by the chemical equation:

Which of the following are not state functions?(I) $q+w$ (II) $q$ (III) $w$ (IV) $H-TS$

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its temperature. The ratio of $\frac{C_p}{C_v}$ for the gas is:

A reaction having equal energies of activation for forward and reverse reactions has:

Bond dissociation enthalpy of ${\text{H}}_2$, ${\text{Cl}}_2$ and $\text{HCl}$ are $434$, $242$ and $431\text{kJ/mol}$ respectively. Enthalpy of formation of $\text{HCl}$ is:

Steam at $100^{\circ }\text{C}$ is passed into $20\text{g}$ of water at $10^{\circ }\text{C}$. When water acquires a temperature of $80^{\circ }\text{C}$, the mass of water present will be: [Take specific heat of water $=1{\text{cal g}}^{-1}{}^{\circ }{\text{C}}^{-1}$ and latent heat of steam $=540{\text{cal g}}^{-1}$ ]

Certain quantity of water cools from $70^{\circ }\text{C}$ to $60^{\circ }\text{C}$ in the first $5\text{minutes}$ and $60^{\circ }\text{C}$ to $54^{\circ }\text{C}$ in the next $5\text{minutes}$. The temperature of the surroundings is:

For the reaction of one mole of zinc dust with one mole of sulphuric acid in a bomb calorimeter, $\Delta U$ and $w$ corresponds to:

For the gas phase reaction ${\text{PCl}}_5(g)\rightleftharpoons {\text{PCl}}_3(g)+{\text{Cl}}_2(g)$, which of the following conditions is correct?

A monoatomic gas at a pressure $P$, having a volume $V$ expands isothermally to a volume $2V$ and then adiabatically to a volume $16V$. The final pressure of the gas is: (take $\gamma =5/3$)

A thermodynamic system undergoes cyclic process $ABCDA$ as shown in figure. The work done by the system in the cycle is:[Image shows a figure of two identical triangles meeting at a point, forming an 8-shape. Loop 1 is clockwise, Loop 2 is anti-clockwise.]

In thermodynamic processes which of the following statements is not true?

Using the Gibbs energy change, $\Delta G^{\circ }=+63.3\text{kJ}$, for the reaction:
$${\text{Ag}}_2{\text{CO}}_3(s)\rightleftharpoons 2{\text{Ag}}^{+}(aq)+{\text{CO}}_3^{2-}(aq)$$
The $K_{sp}$ of ${\text{Ag}}_2{\text{CO}}_3(s)$ in water at $25^{\circ }\text{C}$ is: ($R=8.314{\text{J K}}^{-1}{\text{mol}}^{-1}$)

For the reaction ${\text{X}}_2{\text{O}}_4(l)\to 2{\text{XO}}_2(g)$, $\Delta U=2.1\text{k cal}$ and $\Delta S=20{\text{cal K}}^{-1}$ at $300\text{K}$. Hence, $\Delta G$ is:

For the chemical equilibrium, ${\text{CaCO}}_{3(s)}\rightleftharpoons {\text{CaO}}_{(s)}+{\text{CO}}_{2(g)}$, $\Delta H_r^{\circ }$ can be determined from which one of the following plots?

The internal energy change in a system that has absorbed $2\text{Kcals}$ of heat and done $500\text{J}$ of work is:

The formation of the oxide ion, ${\text{O}}^{2-}(g)$, from oxygen atom requires first an exothermic and then an endothermic step as shown below:$\text{O}(g)+e^{-}⟶{\text{O}}^{-}(g);{\Delta }_f{H}^{\ominus }=-141{\text{kJ mol}}^{-1}$${\text{O}}^{-}(g)+e^{-}⟶{\text{O}}^{2-}(g);{\Delta }_f{H}^{\ominus }=+780{\text{kJ mol}}^{-1}$ Thus the process of formation of ${\text{O}}^{2-}$ in gas phase is unfavourable though ${\text{O}}^{2-}$ is isoelectronic with neon. It is due to the fact that:

The heat of combustion of carbon to ${\text{CO}}_2$ is $-393.5\text{kJ/mol}$. The heat released upon formation of $35.2\text{g}$ of ${\text{CO}}_2$ from carbon and oxygen gas is:

The values of $\Delta H$ and $\Delta S$ for the reaction $\text{C}(\text{graphite})+{\text{CO}}_2(g)\to 2\text{CO}(g)$ are $170\text{kJ}$ and $170{\text{JK}}^{-1}$ respectively. This reaction will be spontaneous at:

Two vessels separately contain two ideal gases $A$ and $B$ at the same temperature, the pressure of $A$ being twice that of $B$. Under such conditions, the density of $A$ is found to be $1.5$ times the density of $B$. The ratio of molecular weight of $A$ and $B$ is:

$4.0\text{g}$ of a gas occupies $22.4$ liters at NTP. The specific heat capacity of the gas at constant volume is $5.0{\text{J K}}^{-1}{\text{mol}}^{-1}$. If the speed of sound in this gas at NTP is $952{\text{m s}}^{-1}$, then the molar heat capacity at constant pressure is (Take gas constant $R=8.3{\text{J K}}^{-1}{\text{mol}}^{-1}$):

An ideal gas heat engine operates in Carnot cycle between 227°C and 127°C. It absorbs 6 x 104 cal of heat at higher temperature. Amount of heat converted to work is :

Identify the correct statement for change of Gibbs energy for a system ($\Delta G_{\text{system}}$) at constant temperature and pressure:

From the following bond energies: $\text{H-H}:431.37\text{kJ/mol}$ $\text{C=C}:606.10\text{kJ/mol}$ $\text{C-C}:336.49\text{kJ/mol}$ $\text{C-H}:410.50\text{kJ/mol}$ Enthalpy for the reaction will be: