Tag: chemistry

Questions Related to chemistry

Like $U$ and $H, S$ is also a state function.

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

  1. True

  2. False

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Correct Option: A
Explanation:

As we know,

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) are state variables.

Internal energy change in a cyclic process is zero.
chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. True

  2. False

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Correct Option: A
Explanation:

The given statement is true.
 Internal energy change in a cyclic process is zero.
Internal energy is a state function. It depends only upon the initial and final states of the system and is independent of the path followed. Hence, for a cyclic process, the initial and final value of the internal energy is same.

Which of the following is a path function?

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

  1. internal energy

  2. enthalpy

  3. work

  4. entropy

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Correct Option: C
Explanation:

Path functions are properties or quantities whose values depends on the transaction of a system from the initial state to the final state. The two most common path functions are heat and work.

Choose the correct answer. 

A thermodynamic state function is a quantity : 

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

  1. used to determine heat chages

  2. whose value is independent of path

  3. used to determine pressure volume work

  4. whose value depends on temperature only

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Correct Option: B
Explanation:

A thermodynamic state function is a quantity whose value is independent of path. Thus, enthalpy is a state function.
Its value depends on iniital and final states and is independatn of path followed.

Among the following, the state function are

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

  1. internal energy

  2. molar enthalpy

  3. reversible expansion work

  4. irreversible expansion work

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Correct Option: A,B
Explanation:

State functions are path Independent

For example: $E$ (Internal energy), Molar enthalpy, entropy etc.

Why are state functions important in chemistry?

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

  1. They appear a lot in thermochemistry and thermodynamics

  2. Many equations include properties that are state functions

  3. We only need to know the final and initial states

  4. They simplify our calculations

  5. All answers are correct

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Correct Option: C
Explanation:
State functions help us simplify our calculations and see the change in value between the final and starting position, also known as a state change. Mass, pressure, density, energy, temperature, volume, enthalpy, entropy, Gibbs free energy and chemical composition are all examples of state functions in thermochemistry
In simple words, the state functions are important in chemistry as we only need to know the final and initial states.

Hence, the correct option is $C$

Which statement is correct?

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

  1. The final destination is not important with state functions

  2. The change in altitude was the same for the train and the hikers, therefore the change in altitude is a state function

  3. The starting point is not important with state functions

  4. The hikers put more effort into climbing therefore the change in altitude is not a state function

  5. None of these
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Correct Option: B
Explanation:

The statement B is correct.
The change in altitude was the same for the train and the hikers, therefore the change in altitude is a state function. The value of state function depend only on initial and final value and is independent of the path followed.

Which statement BEST describes why work is a path function

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

  1. You finish at a different place

  2. You start at a different place

  3. The amount of work varies depending on which path you take to get to the destination

  4. The amount of work is the same whichever path you take to get to the destination

  5. Work is not a path function, it is a state function

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Correct Option: C
Explanation:

The statement (C) BEST describes why work is a path function.
The amount of work varies depending on which path you take to get to the destination.
State function is independent of the pah followed whereas path function is dependent on path followed.

Consider the following reaction, taking place in a container fitted with a movable piston.
$2SO _{2}(g) + O _{2}(g) \rightarrow 2SO _{3}(g)$
Suppose we place two moles each of $SO _{2}$ and $O _{2}$ in the reaction vessel at $25^{\circ}C$, and adjust the volume to give a total pressure of $1.0\ atm$. The reaction is ignited by a spark, and goes to completion. The temperature is returned to $25^{\circ}$.
Which of the following best describes this system after reaction is complete?

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

  1. $SO _{2}$ is limiting. The volume of the system remains the same.

  2. Neither reactant is limiting. The volume of the system decreases.

  3. $SO _{2}$ is limiting. The volume of the system decreases.

  4. $O _{2}$ is limiting. The volume of the system remains the same.

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Correct Option: A

Which describes an endothermic reaction?

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

  1. Positive $\displaystyle \Delta H$

  2. Negative $\displaystyle \Delta H$

  3. Positive $\displaystyle \Delta G$

  4. Negative $\displaystyle \Delta G$

  5. Positive $\displaystyle \Delta S$

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Correct Option: A
Explanation:

The term endothermic process describes a process or reaction in which the system absorbs energy from its surroundings so enthalpy change should be positive