Tag: introduction to thermodynamics

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Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics
State whether the given statement is true or false:

Enthalpy change is dependent on temperature and on the path adopted.

  1. True

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

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

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

  1. True

  2. False

  3. Ambiguous

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

1 : $\Delta U$ is state function.

2: Heat and work are not state functions.

  1. $\text {only 1 is true}$
  2. $\text {only 2 is true}$
  3. $\text {both are true}$
  4. $\text {none of the above}$
Reveal answer Fill a bubble to check yourself
C Correct answer
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 .

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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 $C$