Tag: chemistry

Questions Related to chemistry

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.

Which of the following is path function? 


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

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

  1. A and D

  2. A and B

  3. A, B and D

  4. A, C and D

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Correct Option: B

Identify the state functions from the following:

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

  1. heat

  2. work

  3. enthalpy

  4. none of the above

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Correct Option: C
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.

Among the following, the state functions are:

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

  1. Internal energy

  2. Irreversible expansion work

  3. Reversible expansion work

  4. Molar enthalpy

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Correct Option: A,D
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.

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?

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

  1. P

  2. $2P$

  3. $P/2$

  4. $P^2$

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Correct Option: C
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.