Tag: basics of thermodynamics

Questions Related to basics of thermodynamics

Which of the following are state property?

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

  1. Internal energy (U)

  2. Volume (V)

  3. Heat (q)

  4. Enthalpy (H)

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Correct Option: A,B,D
Explanation:

Internal energy, volume and enthalpy are state properties. Their values are independent of  the path chosen to reach a particular state.
Heat is a path function. Its value depends on the path chosen to reach a particular state.

Identify the state quantity among the following

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

  1. q

  2. q-w

  3. q+w

  4. q/w

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Correct Option: B,C
Explanation:

Both work and heat are path functions. Their values depends on the path chosen to reach a particular state.
However, the change in internal energy is equal to the sum of heat and work. It is a state function. Its value is independent of  the path chosen to reach a particular state.

Identify the state functions.

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

  1. $S$

  2. $q$

  3. $w$

  4. $q+w$

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Correct Option: A,D
Explanation:

Both work and heat are path functions. Their values depends on the path chosen to reach a particular state.
However, the change in internal energy is equal to the sum of heat and work. It is a state function. Its value is independent of  the path chosen to reach a particular state.
Entropy is a state function.  Its value is independent of  the path chosen to reach a particular state.

Which of the following is/are state property/properties?

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

  1. Internal energy

  2. Volume

  3. Heat

  4. Enthalpy

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Correct Option: A,B,D
Explanation:

Heat is a path dependent function.
While internal energy, volume and enthalpy depend only on initial and final stages.
So, these are state properties.

An open system can exchange both matter and energy with surroundings.
chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. True

  2. False

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Correct Option: A
Explanation:

An open system can exchange both matter and energy with surroundings. For example hot tea placed in an open cup constitutes an open system.

A closed vessel contains equal number of oxygen and hydrogen molecules at a total pressure of 740 mm. If oxygen is removed from the system, the pressure -

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

  1. Becomes half of 740 mm.

  2. Remains unchanged

  3. Becomes 1/9th of 740 mm.

  4. Becomes double 740 mm.

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Correct Option: A

Assertion (A): All living systems are examples of a closed system. 

Reason (R): They cannot exchange matter and energy with their surroundings.

Choose the correct option.

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

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are true but R is not the correct explanation of A.

  3. A is true but R is false.

  4. Both A and R are false.

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Correct Option: D
A closed system shows exchange of mass and not energy with surroundings.
chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. True

  2. False

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Correct Option: B
Explanation:

A closed system can exchange energy with surroundings. It cannot exchange mass with surroundings. For example, hot tea placed in a cup which is covered with saucer constitutes a closed system.

Which are extensive properties?

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

  1. $V$ and $E$

  2. $V$ and $T$

  3. $V$ and $Cp$

  4. $P$ and $T$

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Correct Option: A
Explanation:
An extensive property is a property that depends on the amount of matter in a sample. Mass and volume are examples of extensive properties.
Volume and energy both depends on amount of substance.

Hence, the correct option is $A$

Which thermodynamic parameter is not a state function ?

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

  1. q at constant pressure

  2. q at constant volume

  3. W at adiabatic

  4. W at isothermal

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Correct Option: D
Explanation:

$W$ and $q$ are not state functions

$H$ and $U$ are state functions
$\Delta H = \Delta U + \Delta PV$

At constant pressure, $\Delta H = \Delta U + P\Delta V$   $\Delta P = 0$   $\Delta H = q _p$

At constant volume, $\Delta H = \Delta U + V \Delta P$   $\Delta V = 0$   $\Delta U = q _v$

So, the first two options are state function.
$\Delta U = q - W$     $(\because q = 0)$    $[ \therefore$ Adialentic process$]$

$\Delta U = -W$  (state function)
Work done in isotheromal process is not a state
function
$W = -q  (\because \Delta T = 0, q \neq 0)$
$\therefore$ option D is correct.