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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.

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

Which of the following is path function? 


A. $W$
B. $Q$
C. $\Delta G$
D. $\Delta H$

  1. A and D

  2. A and B

  3. A, B and D

  4. A, C and D
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Path functions depend on the process taken to reach a state, not just the state itself. Work (W) and Heat (Q) are path functions, whereas internal energy, enthalpy (H), and Gibbs free energy (G) are state functions.

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

Identify the state functions from the following:

  1. heat

  2. work

  3. enthalpy

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Enthalpy is a state function. Its value depends on the current state of the system and is independent of the path followed to reach that state. Mass, temperature, pressure and volume are also state functions. Heat and work are path functions.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Among the following, the state functions are:

  1. Internal energy

  2. Irreversible expansion work

  3. Reversible expansion work

  4. Molar enthalpy
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation
State function is a quantity in thermodynamics, such as entropy or enthalpy, that has a unique value for each given state of a system. 
(or) 
A State Function is a thermodynamic quantity whose value depends only on the state at the moment, i. e., the temperature, pressure, volume, etc The value of a state function is independent of the history of the system's internal energy. Molar enthalpy and entropy are state quantities because they describe quantitatively an equilibrium state of a thermodynamic, irrespective of how the system arrived in that state.

Hence options A & D are correct.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

A closed vessel contains equal number of nitrogen and oxygen molecules at a pressure of P mm. If nitrogen is removed from the system, then the pressure will be?

  1. P
  2. $2P$
  3. $P/2$
  4. $P^2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\dfrac{p _1}{n _1}=\dfrac{p _2}{n _2}$ (As molecules of $N _2=$ molecules $O _2$)
($\therefore$ Moles $N _2=$moles $O _2$)
As $N _2$ molecules removed$=$ moles become half
$\dfrac{p _1}{1}=\dfrac{p _2}{1/2}$
$p=\dfrac{1}{2}p _1$
$\therefore$ Pressure reduced to half
$\therefore$ Answer is option C.