Tag: chemical thermodynamics

Quizzes (7) Questions (120)

Questions Related to chemical thermodynamics

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

Choose the correct answer. 

A thermodynamic state function is a quantity : 

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

Why are state functions important in chemistry?

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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 $C$
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which statement is correct?

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

Which statement BEST describes why work is a path function

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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?

  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.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to the balanced reaction 2SO2 + O2 -> 2SO3, 2 moles of SO2 react with 1 mole of O2. Since we start with 2 moles of each, SO2 is completely consumed first, making it the limiting reactant. Because 3 moles of gaseous reactants form 2 moles of gaseous products, the total moles of gas decrease, leading to a decrease in the volume of the system at constant pressure.

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

Which describes an endothermic reaction?

  1. Positive $\displaystyle \Delta H$
  2. Negative $\displaystyle \Delta H$
  3. Positive $\displaystyle \Delta G$
  4. Negative $\displaystyle \Delta G$
  5. Positive $\displaystyle \Delta S$
Reveal answer Fill a bubble to check yourself
A Correct answer
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

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

Which of the following statements are correct?

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

Which of the following statements are not true?

  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
Reveal answer Fill a bubble to check yourself
B,D Correct answer
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.

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

Which of the following functions are path independent?

  1. Work

  2. Heat

  3. Gravitational potential energy

  4. Internal energy
Reveal answer Fill a bubble to check yourself
C,D Correct answer
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.