Tag: introduction to thermodynamics

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

Which of the following are state property?

  1. Internal energy (U)

  2. Volume (V)

  3. Heat (q)

  4. Enthalpy (H)
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
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.

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

Identify the state quantity among the following

  1. q

  2. q-w

  3. q+w

  4. q/w
Reveal answer Fill a bubble to check yourself
B,C Correct answer
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.

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

Identify the state functions.

  1. $S$
  2. $q$
  3. $w$
  4. $q+w$
Reveal answer Fill a bubble to check yourself
A,D Correct answer
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.

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

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 -

  1. Becomes half of 740 mm.

  2. Remains unchanged

  3. Becomes 1/9th of 740 mm.

  4. Becomes double 740 mm.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Dalton's Law of Partial Pressures, the total pressure is the sum of the partial pressures of the gases. If the number of molecules is equal, each gas contributes half the total pressure (370 mm each). Removing oxygen leaves only hydrogen, so the pressure becomes 370 mm, which is half of 740 mm.

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

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.

  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.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Living systems are open systems because they constantly exchange both matter (food, waste) and energy (heat, work) with their surroundings. Therefore, both the assertion and the reason are false.

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

Which are extensive properties?

  1. $V$ and $E$
  2. $V$ and $T$
  3. $V$ and $Cp$
  4. $P$ and $T$
Reveal answer Fill a bubble to check yourself
A Correct answer
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 $A$
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which thermodynamic parameter is not a state function ?

  1. q at constant pressure

  2. q at constant volume

  3. W at adiabatic

  4. W at isothermal
Reveal answer Fill a bubble to check yourself
D Correct answer
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.