Chemistry · Physics

Thermodynamics and Chemical Kinetics

1,132 Questions

Thermodynamics and chemical kinetics are crucial branches of physical chemistry. This area focuses on energy transformations, reaction rates, equilibrium constants, and catalysts. These topics carry significant weight in competitive science and engineering examinations.

Enthalpy and energyChemical equilibriumEntropy conceptsReaction kinetics and catalysts

Thermodynamics and Chemical Kinetics Questions

Multiple choice chemistry how far? how fast? collision theory collision theory of chemical reactions rate of chemical reaction

_________ increases effective collisions without increasing average energy.

  1. An increase in the reactant concentration

  2. An increase in the temperature

  3. A decrease in pressure

  4. Catalysts
  5. $\displaystyle pH$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An increase in the reactant concentration increase effective collisions without increasing average energy.

This is due to the fact that molecules comes more and more closer, hence, they tends to collide more easily.

Multiple choice physics free, damped and forced oscillations forced vibration forced vibrations free, forced and damped oscillations

A student performs an experiment for determination of $\Bigg \lgroup g = \frac{4\pi^2 l}{T^2} \Bigg \rgroup$, l = 1m, and he commits an error of $\Delta l$ For T he takes the time of n oscillations with the stop watch of least count $\Delta T$ and he commits a human error of 0.1 s. For which of the following data, the measurement of g will be most accurate?

  1. $\Delta L = 0.5, \ \Delta T = 0.1 , \ n = 20$
  2. $\Delta L = 0.5, \ \Delta T = 0.1 , \ n = 50$
  3. $\Delta L = 0.5, \ \Delta T = 0.01 , \ n = 20$
  4. $\Delta L = 0.5, \ \Delta T = 0.05 , \ n = 50$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is given that $g$ is determined by $:g = \frac{{4{\pi ^2}l}}{{{T^2}}}$

Taking log and differentiating$,$
$ \Rightarrow \frac{{\Delta g}}{g} = \frac{{\Delta l}}{l} + \frac{{2\Delta T}}{T}$ 
Now$,$ $g$ is most accurate in the case in which error in $g\left( {l.e\,\Delta g} \right)$ is minimum$.$ In case $B,$ number of repetitions to perform the experiment is maximum and ${\Delta g}$  is minimum$.$
Hence,
option $(B)$ is correct answer.

Multiple choice

Chemical changes cause

  1. Does not make a difference

  2. Production of a new substance

  3. Only changes color

  4. Only Changes it's temperature
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A chemical change occurs when substances react to form one or more new substances with different chemical properties.

Multiple choice chemistry lattice energy born-haber cycle born-haber cycles energy cycles

Consider the following reaction,
$2A + B \rightarrow C + 2D$, $\Delta H _{1} = 10$
$A + 2C \rightarrow 2D + B$, $\Delta H _{2} = -5$ What is $\Delta H$ of reaction $A + 2B \rightarrow 3C$?

  1. $-5$
  2. $+5$
  3. $+10$
  4. $+15$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Solution:- (D) $+15$
$A + 2B \longrightarrow 3C \quad \Delta{H} = ?$
Given:-
$2A + B \longrightarrow C + 2 D \quad \Delta{{H} _{1}} = 10 ..... \left( 1 \right)$
$A + 2C \longrightarrow 2D + B \quad \Delta{{H} _{2}} = -5$
$B + 2D \longrightarrow A + 2C \quad \Delta{{H} _{3}} = - \Delta{{H} _{2}} = 5 ..... \left( 2 \right)$
Adding ${eq}^{n} \left( 1 \right) \& \left( 2 \right)$, we have
$2A + B + B + 2D \longrightarrow C + 2D + A + 2C \quad \Delta{H} = 10 + 5$
$A + 2B \longrightarrow 3C \quad \Delta{H} = 15$
Hence the $\Delta{H}$ for the given reaction is $+15$.
Multiple choice chemistry lattice energy born-haber cycle born-haber cycles energy cycles

Choose the correct statement about the process (I) and (II).


$\displaystyle Na^{+} _{(g)}\xrightarrow{(I)}Na _{\left ( g \right )} \xrightarrow {(II)}Na _{\left ( s \right )}$

  1. In $(I)$ energy released. $(II)$ energy absorbed
  2. In both $(I)$ and $(II)$ energy is absorbed
  3. In both $(I)$ and $(II)$ energy is released
  4. In $(I)$ energy absorbed, $(II)$ energy released
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The first process represents the electron affinity of $\displaystyle Na^+ $  ion which is negative.
The second process represents sublimation of $Na$. The sublimation energy is negative.
Thus, in both the processes, the energy is released.


Hence, the correct option is C.

Multiple choice chemistry lattice energy born-haber cycle born-haber cycles energy cycles

The heat change for the reaction: $C(s) + S(s)\rightarrow CS _2(l)$, known as:

  1. heat of transition

  2. heat of fusion

  3. heat of vapourisation

  4. heat of formation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
$C(s)+2S(s)\rightarrow CS _2(l)$
The heat change of the reaction is enthalpy of formation as 1 mole of $CS _2$ is being formed from elemental state of carbon as well as Sulphur.
Multiple choice chemistry phenomena around us comparison between physical and chemical changes introduction to physical and chemical changes change around us

In the_______ properties of molecules remain same even after the change.

  1. physical change

  2. chemical change

  3. biochemical change

  4. photochemical change
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In physical change properties of molecules remain the same even after the change. Physical properties like colour, density, volume, mass, boiling point, melting point only have an effect on their physical nature, the chemical nature of the substance remains the same. Physical properties are used to observe and describe matter.

Multiple choice chemistry phenomena around us comparison between physical and chemical changes introduction to physical and chemical changes change around us

Choose the incorrect statement :

  1. Physical change is reversible

  2. Physical change results in the formation of new substances

  3. Chemical change is permanent

  4. Physical change is accompanied by energy change
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Physical change does not lead to formation of new substances but only chemical changes can produce new substances.

Multiple choice chemistry phenomena around us comparison between physical and chemical changes introduction to physical and chemical changes change around us

Physical changes require _______ energy than chemical changes.

  1. less

  2. more

  3. equal amount of

  4. very high amount of
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Physical changes require less energy than chemical energies, as they does not involve in making and breaking of bonds as in the case of chemical bonds, which require a lot of energy.

Multiple choice chemistry phenomena around us comparison between physical and chemical changes introduction to physical and chemical changes change around us

The difference between a physical reaction and a chemical reaction is :

  1. composotion

  2. size

  3. shape

  4. all of above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The difference between a physical reaction and a chemical reaction is composition. In a chemical reaction, there is a change in the composition of the substances. In a physical change, there is a difference in the appearance, smell, or simple display of a sample of matter without a change in composition. 

Multiple choice chemistry phenomena around us comparison between physical and chemical changes introduction to physical and chemical changes change around us

Which statement best describes the difference between the two equations shown below?
Equation I: $H _{2}O _{(l)} \rightarrow H _{2}O _{(g)}$
Equation II: $2H _{2}O _{(l)} \rightarrow 2H _{2(g)} + O _{2(g)}$

  1. Equation I represents a physical change because intermolecular forces are broken during the process, where Equation II presents a chemical change because intramolecular forces are broken.

  2. Equation I represents a physical change because intramolecular forces are broken during the process, whereas in Equation II a chemical change because intermolecular forces are broken.

  3. Equation I represents a chemical change because intermolecular forces are broken, and Equation II represents a physical change because intramolecular forces are broken.

  4. Equation I represents a chemical change because intramolecular forces are broken, and Equation II represents a physical change because intermolecular forces are broken.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$(I)$  ${ H } _{ 2 }{ O } _{ \left( l \right)  }\longrightarrow { H } _{ 2 }{ O } _{ \left( g \right)  }$   physical change (reversible)

intermolecular force (Hydrogen bonding) is broken during the process.
$(II)$ $2{ H } _{ 2 }{ O } _{ \left( l \right)  }\longrightarrow 2{ H } _{ 2\left( g \right)  }+{ O } _{ 2\left( g \right)  }$ 
it is a chemical change as it is changing the composition of molecule. Intramolecular forces (Bond breaking) are broken during the process.

Multiple choice chemistry phenomena around us comparison between physical and chemical changes introduction to physical and chemical changes change around us

All of the following could represent a physical process except:

  1. Formation of a gas

  2. A release of energy from a system into the surroundings

  3. The appearance of substances in two phases of matter at the same time

  4. Appearance of a smell that was no previously present
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Formation of gas not a physical change because some reactions has taken place which leads to the formation of gas hence, it is a chemical change.

Whereas all the three are physical changes, as they are not producing any new products.

Multiple choice physics behaviour of perfect gas and kinetic theory of gases mean free path law of equipartition of energy and mean free path behavior of perfect gas and kinetic theory

Mean free path depends on which of the following?

  1. size of the molecule

  2. density of the molecule

  3. diameter of the molecule

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The mean free path or average distance between collisions for a gas molecule may be estimated from kinetic theory.

Mean free path displays linear proportionality to the temperature and inverse proportionality to the pressure and molecular diameter.
Mathematically it is expressed as:
$l.p=\dfrac{kT}{\sqrt{2}\pi d _m^2}$

Multiple choice physics energy transformations and energy transfers law of conservation of energy the law of conservation of energy types of energy

According to the law of conservation of energy:

  1. energy exists in only one form

  2. energy can be created but not destroyed and it can be transformed from one form to another

  3. energy exists in many forms but it cannot be transformed

  4. energy can neither be produced nor be destroyed and it can be transformed from one form to another
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The law of conservation of energy states that the total amount of energy in a system remains constant ("is conserved"), although energy within the system can be changed from one form to another or transferred from one object to another.

Energy cannot be created or destroyed, but it can be transformed.

Multiple choice physics energy transformations and energy transfers law of conservation of energy the law of conservation of energy types of energy

According to law of conservation of energy :

  1. energy can be created but not destroyed and it can be transformed from one form into another

  2. energy exists in only one form

  3. energy exists in many forms but it cannot be transformed

  4. energy can neither be created nor be destroyed but can be changed into different forms
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Law\ of conservation\ of\ energy$ states that the total energy of an isolated system remains constant and it is said to be conserved over time. Energy can neither be created nor be destroyed, but it can be transformed from one form to another, for instance, chemical energy can be converted to kinetic energy in the explosion of a stick of dynamite.