Tag: chemical thermodynamics

Questions Related to chemical thermodynamics

Which one of the following systems is an example of a closed system?

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

  1. Some amount of water in equilibrium with its vapour in a closed and insulated vessel

  2. Some amount of hot water enclosed in a closed container which is not insulated

  3. Hot water contained in an open vessel

  4. None of the above

Show answer
Correct Option: B
Explanation:

When some amount of water is in equilibrium with its vapour in a closed but non insulated vessel, then it will be an example of closed system.

Which of the following is not a state function?

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

  1. U

  2. P

  3. V

  4. q

Show answer
Correct Option: D
Explanation:

State variables : To define a thermodynamics states of a system, we have to specify the values of certain mesurable quantities. These are called thermodynamic  variable or state variable. 
A system can be completely defined by four variables namely pressure, temperature, volume and composition. A system is said to be in a certain definite state when all of its properties have definite value. 
Between two fixed state the change in the value of state function is same irrespective of the path connection two states. 
Differential of a state function  integerated over a cyclic path returns zero. 
In other words summation of change in state function in a cyclic process is equal to zero.
Example : T, V, P and U (internal energy), H (enthalpy), S are state variables.

Warming ammonium chloride with sodium hydroxide in a test tube is an example of:

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

  1. closed system

  2. isolated system

  3. open system

  4. none of these

Show answer
Correct Option: C
Explanation:

When we are warming ammonium chloride with sodium hydroxide in a test tube, there is exchange of heat as well as mass between system and surrounding. Mass is transferred from the open end of the test tube due to evaporation. Also heat is being exchanged through the walls of test tube.

Which of the following is not a state function?


a. $U + PV$      b. $q + w$     c. $\cfrac { q _ {rev} }{ T }$       d. $q$

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

  1. a

  2. b

  3. c

  4. d

Show answer
Correct Option: D
Explanation:

State variables : To define a thermodynamics states of a system, we have to specify the values of certain mesurable quantities. These are called thermodynamic  variable or state variable.
A system can be completely defined by four variables namely pressure, temperature, volume and composition. A system is said to be in a certain definite state when all of its properties have definite value.
Between two fixed state the change in the value of state function is same irrespective of the path connection two states.
Differential of a state function  integerated over a cyclic path returns zero.
In other words summation of change in state function in a cyclic process is equal to zero.
Example : T, V, P and U (internal energy), H (enthalpy), S are state variables.

Which of the following is not a state function?

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

  1. Temperature

  2. Density

  3. Work

  4. Volume

Show answer
Correct Option: C
Explanation:

Work is not a state function. Work is a path function. Work depends on the distance or path followed by an object.

Thus option C is the correct answer.

When you combust $100.0\ g$ of propane at $500.K$ and $1.00\ atm$ in a closed container, you expected to collect $279\ L$ of carbon dioxide. Instead, when you collect the gas, it measures $651\ L$ in total.
Why have you collected more than your predicted, theoretical yield?

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

  1. The theoretical yield was calculated incorrectly.

  2. The graduated cylinder used to collect the gas was read incorrectly.

  3. You did not account for the surrounding volume of air.

  4. You did not account for the volume of water vapor that was produced.

Show answer
Correct Option: A
Explanation:

$\text{The theoretical yield was calculaterd incorrectly.}$

For a reaction to be spontaneous in neither direction, which of the following is/are correct regarding the closed system?
(1) ${ \left( \Delta { G } \right)  } _{ T,P }=0$
(2)${ \left( \Delta { G } \right)  } _{ T,P }< 0$
(3) ${ \left( \Delta { G } \right)  } _{ U,V }=0$
(4) ${ \left( \Delta { G } \right)  } _{ U,V }>0$
Codes:

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

  1. 1,2,3 are correct

  2. 1 and 2 are correct

  3. 2 and 4 are correct

  4. 1 and 3 are correct

Show answer
Correct Option: D
Explanation:

$\text{For spontaneous in neither direction:}$

(1) ${ \left( \Delta { G } \right)  } _{ T,P }=0$
(3) ${ \left( \Delta { G } \right)  } _{ U,V }=0$
$\text{is correct.}$

Select the state functions among the following:

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

  1. temperature

  2. entropy

  3. work

  4. enthalpy

Show answer
Correct Option: A,B,D
Explanation:

State function is defined as a system that depends upon the initial and final positions,

so temperature , entropy and enthalpy depends upon the initial and final state, so they are state function but work depends upon the area of PV curve.

A system where there is exchange of energy but not of mass is called _________ system.

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

  1. insulated

  2. isolated

  3. open

  4. closed

Show answer
Correct Option: D
Explanation:

In thermodynamics, a closed system can exchange energy (as heat or work) but not matter, with its surroundings. An isolated system cannot exchange any heat, work, or matter with the surroundings, while an open system can exchange energy and matter.

Temperatures of two hot bodies $B _{1}$ and $B _{2}$ are $100^{\circ}C$ and $80^{\circ}C$ respectively. The temperature of surrounding is $40^{\circ}C$. At $t = 0$, the ratio of rates of cooling of the two bodies (liquid) $R _{1} : R _{2}$ will be:

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

  1. $3 : 2$

  2. $5 : 4$

  3. $2 : 1$

  4. $4 : 5$

Show answer
Correct Option: A
Explanation:

Rate of cooling=$\cfrac { dQ }{ dt } \propto \quad \Delta T$ 

$\therefore \cfrac { { R } _{ 1 } }{ { R } _{ 2 } } =\cfrac { { \Delta T } _{ 1 } }{ { \Delta T } _{ 2 } } =\cfrac { 100-40 }{ 80-40 } =\cfrac { 60 }{ 40 } =\cfrac { 3 }{ 2 } $