Tag: basics of thermodynamics

Questions Related to basics of thermodynamics

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

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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

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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

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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

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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. $4 : 5$

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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 } $

Universe is :

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

  1. Closed system

  2. Open system

  3. Receiving constant supply of energy.

  4. Dissipating energy continuously.

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Correct Option: A
Explanation:

A closed system is one which can only exchange energy. The entire universe is an isolated system because it has no surrounding. Hence it is a closed system.

In a closed insulator container, a liquid is stirred with a paddle to increase the temperature. Which of the following is true?

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

  1. $\triangle U=w\neq O,q=O$

  2. $\triangle U=w=q\neq O$

  3. $\triangle U=O,w=q\neq O$

  4. $w=O,\triangle U=q\neq O$

Show answer
Correct Option: A
Explanation:

A closed insulated container, a liquid is stirred with a paddle to increase the temperature, therefore it behave as adiabatic system, $q=0$

$\Delta U=q+w$
$\implies \Delta U=w\neq 0$

For an isolated system, the entropy:

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

  1. Either increases or remains constant

  2. Either decreases or remains constant

  3. Can never decrease

  4. Can never increase

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Correct Option: A
Explanation:

The second law of thermodynamics states that the entropy of an isolated system never decreases, because isolated systems always evolve toward thermodynamic equilibrium, a state with maximum entropy.