Tag: chemistry

Questions Related to chemistry

If a closed system has adiabatic boundaries, then atleast one boundary must be:

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

  1. permeable

  2. imaginary

  3. movable

  4. fixed

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Correct Option: C
Explanation:
Adiabatic boundaries mean there is no heat that is evolved or no heat exchange possible through it.

So, our system is closed that means matter cannot be exchanged but heat exchange can happen.

As here all the boundaries are adiabatic so to remain system closed at least one boundary should be movable to that heat exchange can take place.

Option C is correct.

Which of the following statement is correct?

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

  1. Heat is thermodynamic property of system.

  2. Work is thermodynamic property of system.

  3. Work done by a conservative force is path function.

  4. Heat involved in chemical reaction is path independent physical quantity.

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Correct Option: D
Explanation:
Heat and work are not thermodynamic properties and work done is independent of the object's path in a conservative force.

So, a,b,c are incorrect

A heat involved in the chemical reaction is path independent which is correct (from Hess's law)

Option D is correct.

The open system(s) is/are which

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

  1. can exchange matter with the surroundings

  2. can exchange energy with the surroundings

  3. can exchange both matter and energy with the surroundings

  4. cannot exchange either matter or energy with the surroundings

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Correct Option: A,B,C
Explanation:

Types of system : 
(i)Closed system : A system which can exchange only energy with surrounding. 
(ii)Open system : A system which can exchange both energy and matter with surrounding. 
(iii)Isolated system : A system which cannot exchange matter or energy with surrounding.

The enthalpy change for a reaction does not depend upon the:

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

  1. physical states of reactants and products

  2. use of different reactants for the same product

  3. nature of intermediate reaction steps

  4. difference in initial or final temperature of involved substances

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Correct Option: C
Explanation:

$\triangle H$ depends on :

  • Physical states of reactant and product.
  • Use of different reactants for the same product.
  • Difference in initial or final temperature of involved substances.
It is independent of nature of intermediate reaction steps because it is a path independent & is a state function.

The change in enthalpy, $\Delta H$ accompanying a process depends on the path followed.
chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. True

  2. False

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Correct Option: B
Explanation:

The change in enthalpy, $\Delta H$ accompanying a process does not depends on the path followed.
This is because the enthalpy of a reaction is a state function and its value depends on the inital and final states only.

  Column I   Column II
a. Enthalpy p. Intrinsic property
b. Temperature q. Path function
c. Free energy r. Function $U, P, V$
d. Work s. State function
chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. $(a - r,s), (b - p,s), (c - r,s), (d - q)$

  2. $(a - r), (b - s), (c - r,s), (d - q, r)$

  3. $(a - r,s), (b - r), (c - p,s), (d - q)$

  4. $(a - q), (b - p,s), (c - s), (d - q, s)$

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Correct Option: A
Explanation:

$(a\rightarrow r,s)$ Enthalpy is a state function and is a function of internal energy and pressure and volume.
$(b\rightarrow p,s)$ Temperature is independent of the bulk matter of the system and hence it is an intrinsic property but it is a state variable.
$(c\rightarrow r,s)$ Free energy is a state function as it depends on the state of the system as well as it depends on $H, T$ and $S$. It is also a function of $U, P$ and $V$.
$(d\rightarrow q)$ Work is a path function as the amount of work done depends upon path undertaken.

State whether the given statement is true or false:

Enthalpy change is dependent on temperature and on the path adopted.
chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. True

  2. False

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Correct Option: B
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.

Example : T, V, P and U (internal energy), H (enthalpy) are state variables.
As enthalpy is state variable so it will depend upon temperature only, not on path.

A system which cannot exchange matter and energy with the surroundings called isolated.

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

  1. True

  2. False

  3. Ambiguous

  4. None of these

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Correct Option: A
Explanation:

A system which  cannot exchange matter and energy with the surroundings called isolated system.
A liquid in a sealed thermos flask and ice in a thermos flask are examples of isolated systems.

Which one of the following quantity is dependent on path?

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

  1. Molar internal energy

  2. Volume

  3. W

  4. Q+W

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Correct Option: C
Explanation:

Work is a path dependent quantity. It is known as a path function.

1 : $\Delta U$ is state function.

2: Heat and work are not state functions.

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

  1. $\text {only 1 is true}$

  2. $\text {only 2 is true}$

  3. $\text {both are true}$

  4. $\text {none of the above}$

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Correct Option: C
Explanation:

$\Delta U$ and heat are state functions. Their values depends only on the state of the system and are independent of the path followed. Work is a path function. Its value depends on the path followed .