Tag: chemical thermodynamics

Quizzes (7) Questions (120)

Questions Related to chemical thermodynamics

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

System in which there is no exchange of matter, work or energy from surroundings is:

  1. closed

  2. adiabatic

  3. isolated

  4. isothermal
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Closed System - The system in which only energy can be exchanged with the surrounding.


Adiabatic - The process in which heat is not exchanged by the system with the surroundings, i.e., $Q=0$.


Isolated - The system in which neither energy nor matter can be exchanged with the surroundings.  

Isothermal - The temperature remains constant, i.e., $\Delta T=0$.


Hence, the correct answer is option $\text{C}$.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

In a closed system : $A\left( s \right) \rightleftharpoons 2B\left( g \right) +3C\left( g \right) $ if the partial pressure C is of doubled then partial pressure B wil be:

  1. Twice the original pressure

  2. Half of its original pressure
  3. $\dfrac { 1 }{ 2\sqrt { 2 } } $ times, the original pressure
  4. $2\sqrt { 2 } $ times its original pressure
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Solution:- (C) $\cfrac{1}{2 \sqrt{2}}$ times, the original pressure
${A} _{\left( s \right)} \rightleftharpoons 2 {B} _{\left( g \right)} + 3 {C} _{\left( g \right)}$
${K} _{P} = {\left( {P} _{B} \right)}^{2} {\left( {P} _{C} \right)}^{3} ..... \left( 1 \right)$
If we double the partial pressure of $C$, i.e., ${P} _{C}' = 2 {P} _{C}$
$\therefore {K} _{P}' = {\left( {P} _{B}' \right)}^{2} {\left( {P} _{C}' \right)}^{3}$
$\Rightarrow {K} _{P}' = {\left( {P} _{B}' \right)}^{2} {\left( 2 {P} _{C} \right)}^{3}$
$\Rightarrow {K} _{P}' = 8 {\left( {P} _{B}' \right)}^{2} {\left( {P} _{C} \right)}^{3}$
Since ${K} _{P}$ is constant,
$\therefore {K} _{P} = {K} _{P}'$
$\Rightarrow {\left( {P} _{B} \right)}^{2} {\left( {P} _{C} \right)}^{3} = 8 {\left( {P} _{B}' \right)}^{2} {\left( {P} _{C} \right)}^{3}$
$\Rightarrow {P} _{B}' = \sqrt{\cfrac{{P} _{B}}{8}}$
$\Rightarrow {P} _{B}' = \cfrac{{P} _{B}}{2 \sqrt{2}}$
Hence the partial pressure of $B$ will be $\cfrac{1}{2 \sqrt{2}}$ times of its original pressure.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which of the following statement is correct?

  1. The presence of reaction species in a covered beaker is an example of open system.

  2. There is an exchange of energy as well as matter between the system and the surroundings in a closed system.

  3. The presence of reactants in a closed vessel made up of copper is an example of a closed system.

  4. The presence of reactants in a thermos flask or any other closed insulated vessel is an example of a closed system.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In a closed system (For example, the presence of reactants in a closed vessel made of conducting material e.g copper) there is no exchange of matter, but exchange of energy is possible between system and the surroundings.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

The state of gas can be described by quoting the relationship between_____________.

  1. pressure, volume, temperature

  2. temperature, amount, pressure

  3. amount, volume, temperature

  4. pressure, volume, temperature, amount
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pressure $(P)$, volume $(V)$, temperature $(T)$, amount $(n)$ etc. are the state variables or state functions.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Select incorrect statement(s):

  1. A closed system with all adiabatic boundaries must be an isolated system

  2. Total heat exchange in a cyclic process may be zero

  3. Entropy of a closed system is maximum at equilibrium

  4. Molar gibb's Energy is an extensive property
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Since heat is energy, only two systems can stop it from crossing the boundary closed and isolated system. So yes, adiabatic process can happen in an isolated system. But all adiabatic process need not happen in an isolated system, it can happen in a closed system also.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Two closed vessel $A$ and $B$ of equal volume of $8.21L$ are connected by a narrow tube of negligible volume with open valve. The left hand side container id found to contain $3\ mole \, CO _2$ and $2\ mole$ of $He$ at $400K$. What is the partial pressure of $He$ in vessel $B$ at $500K$?

  1. 2.4 atm

  2. 8 atm

  3. 12 atm

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

partial pressure of $He$ in vessel $B$, 

$PV = nRT$
$P _{He} = \dfrac{nRT}{V} = \dfrac{2\times 8.314\times 400}{8.21} =8atm$

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Ammonium carbamate dissociates as ${ NH } _{ 2 }COON{ H } _{ 4\left( s \right)  }\leftrightharpoons 2N{ H } _{ 3\left( g \right)  }+{ CO } _{ 2\left( g \right)  }$. In a closed vessel containing ammonium carbamate in equilibrium, ammonia is added such that the partial pressure of ${ NH } _{ 3 }$ now equals to the original total pressure. The ratio of total pressure now to the original pressure is :

  1. $\frac { 27 }{ 31 } $
  2. $\frac { 31 }{ 27 } $
  3. $\frac { 4 }{ 9 } $
  4. $\frac { 5 }{ 9 } $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For the reaction NH2COONH4(s) <=> 2NH3(g) + CO2(g), the initial equilibrium partial pressures are P(NH3) = 2p and P(CO2) = p, so total pressure P1 = 3p. After adding NH3, the new P(NH3) = 3p. Using Kp = (2p)^2 * p = 4p^3, the new equilibrium satisfies 4p^3 = (3p)^2 * P(CO2_new), giving P(CO2_new) = 4p/9. The new total pressure P2 = 3p + 4p/9 = 31p/9. The ratio P2/P1 = (31p/9) / 3p = 31/27.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

If the density of a certain gas at $30^oC$ and $768 \ torr$ is $1.35 \ kg/{m}^{3}$, the density at STP would be:

  1. $1.48 \ kg/{m}^{3}$
  2. $1.58 \ kg/{m}^{3}$
  3. $1.25 \ kg/{m}^{3}$
  4. $1.4 \ kg/{m}^{3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
From Ideal gas law,

$PM = dRT$

$P _1 = 768\ torr$
$T _1 = 30^0\ C = 303\ K$
$d _1 = 1.35 kg/ m^3$

At STP, 
$T _2 = 273\ K$
$P _2 = 760\ torr$

$\dfrac{P _1}{P _2} = \dfrac{d _1T _1}{d _2T _2}$

$\dfrac{768}{760} = \dfrac{1.35\times 303}{d _2\times 273}$

$d _2 = 1.48 kg/m^3$

Hence, option A is correct.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

$5$ moles of $SO _{2}$ and 5 moles of $O _{2}$ are allowed to react to form $SO _{3}$  in a closed vessel. At the equilibrium stage, $60\%$ $SO _{2}$ is used up. The total number of moles of $SO _{2}$, $O _{2}$ and $SO _{3}$ in the vessel now is

  1. $10.5$
  2. $10.0$
  3. $8.5$
  4. $3.9$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Initially, we have 5 moles of SO2 and 5 moles of O2. Since 60 percent of SO2 is used up, 0.60 times 5 equals 3 moles of SO2 reacted. Using stoichiometry (2 SO2 + O2 -> 2 SO3), 3 moles of SO2 require 1.5 moles of O2 and produce 3 moles of SO3. The remaining moles are: SO2 = 5 - 3 = 2, O2 = 5 - 1.5 = 3.5, and SO3 = 3, giving a total of 2 + 3.5 + 3 = 8.5 moles.