Tag: system and surroundings

Questions Related to system and surroundings

In a closed system :

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

  1. energy is not exchanged

  2. matter is exchanged

  3. energy is only exchanged

  4. energy and matter are exchanged

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Correct Option: C
Explanation:

In a closed system Matter is not exchanged but Energy is exchanged.

So option c is correct

Which of the following is a state function ?

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

  1. $q\times w$

  2. $q+w$

  3. $\dfrac{q^2}{w^2}$

  4. $\sqrt{qw}$

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Correct Option: B
Explanation:

Solution:- (B) $q + w$

From first law of thermodynamics,
$\Delta{U} = q + w$
As we know that $\Delta{U}$ is a state function, thus we can say that $q + w$ is a state function.

The following two equilibria exist simultaneously in a closed vessel :
$PCI _5(g) \rightleftharpoons PCI _3(g) + Cl _2(g)$
$COCI _2(g) \rightleftharpoons CO (g) + CI _2 (g)$
If some CO is added into the vessel, then after the equlibrium is attained again, concertration of ?

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

  1. $PCI _5$ will increase

  2. $PCI _5$ will decrease

  3. $PCI _5$ will remain unaffected

  4. $CI _2$ will increase

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Correct Option: C
Explanation:

Given reactions are,

$PCl _5 \rightleftharpoons PCl _3+Cl _2$
$COCl _2\rightleftharpoons CO _{(g)}+Cl _2$
If some $CO$ is added into the vessel, the concentration of $PCl _5$ will remain unaffected, because $CO$ reacts with $Cl _2$ and forms $COCl _2$, not going to effect the concentration of $PCl _5$ .

Bond dissociation enthalphies of ${ H } _{ 2 }\left( g \right) $ and ${ N } _{ 2\left( g \right)  }$ are enthalpy of formation of $N{ H } _{ 3 }\left( g \right) $ is $-46 kJ mol^{-1}$. What is enthalpy of atomization of $N{ H } _{ 3 }\left( g \right) $?

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

  1. $390.3 kJ mol^{-1}$

  2. $1170.9kJ mol^{-1}$

  3. $590 kJ mol^{-1}$

  4. $720 kJ mol^{-1}$

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Correct Option: B

Identify the 'State function' among the following

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

  1. q

  2. q $\times$ W

  3. q/W

  4. q + W

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Correct Option: 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 which is equal to the sum of heat and work, is a state function. Its value is independent of  the path chosen to reach a particular state.

Which is not a state function ?

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

  1. Internal energy

  2. Entropy

  3. Work

  4. Enthalpy

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Correct Option: C
Explanation:

Heat and work are not state functions. Work can't be a state function because it is proportional to the distance an object is moved, which depends on the path used to go from the initial to the final state.

An isolated system is one which neither shows an exchange of _nor _with surroundings.

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

  1. heat, mass

  2. heat, temperature

  3. temperature, mass

  4. None of these

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Correct Option: A
Explanation:
Heat, mass

In physical science, an isolated system is either 

(1) a thermodynamic system which is completely enclosed by walls through which can pass neither matter nor energy, though they can move around inside it; or 

(2) a physical system so far removed from others that it does not interact with them.

Hence, option A is correct.

Which one of the following systems is an example of a closed system?

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

  1. Some amount of water in equilibrium with its vapour in a closed and insulated vessel

  2. Some amount of hot water enclosed in a closed container which is not insulated

  3. Hot water contained in an open vessel

  4. None of the above

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Correct Option: B
Explanation:

When some amount of water is in equilibrium with its vapour in a closed but non insulated vessel, then it will be an example of closed system.

Which of the following is not a state function?

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

  1. U

  2. P

  3. V

  4. q

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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.

Warming ammonium chloride with sodium hydroxide in a test tube is an example of:

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

  1. closed system

  2. isolated system

  3. open system

  4. none of these

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Correct Option: C
Explanation:

When we are warming ammonium chloride with sodium hydroxide in a test tube, there is exchange of heat as well as mass between system and surrounding. Mass is transferred from the open end of the test tube due to evaporation. Also heat is being exchanged through the walls of test tube.