Tag: chemistry

Questions Related to chemistry

Which of the following statements are correct?

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

  1. $\Delta H$ is a state function

  2. Value of $\Delta H $ is independent of path taken

  3. $\Delta H$ can be determined under standard condition

  4. All of the above

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Correct Option: D
Explanation:

Change in enthalpy $\triangle H$ is a state function as its value doesn't depend on the path taken i.e. they give a unique value for each given state of a system. Since it gives value independent of path taken, its value at standard condition can be determined(25℃ and 1atm)
Hence all statements are correct.

Which of the following statements are not true?

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

  1. Heat is a macroscopic physical property

  2. Heat is an intrinsic property of a body

  3. Heat is stored in a body as internal energy

  4. Heat is path independent

Show answer
Correct Option: B,D
Explanation:

An intrinsic property is a property of a system or of a material itself or within. It is independent of how much of the material is present and is independent of the form of the material. Heat flow is a results of a temperature difference between two bodies hence, it is not an intrinsic property of substance.

Two important examples of a path function are heat and work. These two functions are dependent on how the thermodynamic system changes from the initial state to final state.

Which of the following functions are path independent?

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

  1. Work

  2. Heat

  3. Gravitational potential energy

  4. Internal energy

Show answer
Correct Option: C,D
Explanation:

In thermodynamics, a state function or function of state is a function defined for a system relating several state variables or state quantities that depends only on the current equilibrium state of the system. State functions do not depend on the path by which the system arrived at its present state. A state function describes the equilibrium state of a system.

For example, internal energy, enthalpy, Gravitational potential energy and entropy are state quantities because they describe quantitatively an equilibrium state of a thermodynamic system, irrespective of how the system arrived in that state.

Which of the following is path function?

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

  1. Work

  2. Specific volume

  3. Pressure

  4. Temperature

Show answer
Correct Option: A
Explanation:

In thermodynamics, a state function or function of state is a function defined for a system relating several state variables or state quantities that depends only on the current equilibrium state of the system. State functions do not depend on the path by which the system arrived at its present state. A state function describes the equilibrium state of a system.

Hence, work is a path function and not state function.

An isolated system is that system in which:

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

  1. there is no exchange of energy with the surroundings

  2. there is exchange of mass and energy with the surroundings

  3. there is no exchange of energy and mass with the surroundings

  4. there is exchange of energy and mass with the surroundings

Show answer
Correct Option: C
Explanation:

An isolated system is a thermodynamic system that cannot exchange either energy or matter (mass) outside the boundaries of the system. An isolated system differs from a closed system by the transfer of energy. Closed systems are only closed to matter, energy can be exchanged across the system's boundaries.
Hence, correct answer is option C. 

Steady state is represented by :

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

  1. Getting raw materials.

  2. Intake of food and energy.

  3. Intake of materials and energy, elimination of wastes and dissipation of energy.

  4. Removal of waste products and intake of raw materials.

Show answer
Correct Option: C
Explanation:
Living beings require energy for their day to day activity. They generally consume food for intake of energy. They generally consume food for intake of energy, The utilize energy and eliminate the rest of the waste.
In the whole process, there is no change in energy and mass. Hence it can be considered as a steady state.
To get clear understanding of steady state read the following example:
When the drain of bathtub is open and water is being added into the bathtub at same rate, then the amount of water in the bathtub is constant.
Water draining=Water added
It is a steady state as the state variable volume is constant overtime.

Which of the following state function not zero at standard state?

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

  1. Enthalpy

  2. Entropy

  3. Free energy

  4. None of the above

Show answer
Correct Option: B,C
Explanation:

Solution:- (B) entropy and (C) free energy

Entropy and free energy are the state function which are not zero at standard state.

Work is __________ function.

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

  1. path

  2. state 

  3. both path and state

  4. none of these

Show answer
Correct Option: A
Explanation:

Work is a path function and not a state function. The amount of work done is different for different paths although the initial and final states are the same. The amount of work depends on the path connecting the initial and final states.

Which of the following is/are not state function?

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

  1. $q$

  2. $q-w$

  3. $\cfrac { q }{ w } $

  4. $q+w$

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Correct Option: A,B,C

A system absorbs 186 kJ of heat and the surroundings do 120 kJ of work on the system. What is the change in internal energy of the system? Express the internal energy in kilojoules to three significant figures.

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

  1. $440KJ$

  2. $360KJ$

  3. $120.32J$

  4. $-200J$

Show answer
Correct Option: B