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 physics heat engine: second law of thermodynamics second law of thermodynamics the second law of thermodynamics second law of thermodynamic

Which of the following statement is true as per the second law of thermodynamics for an isolated, ordered system?

  1. Heat will flow into the system

  2. Heat will flow out of the system

  3. Work will be done by the system

  4. Work will be done on the system

  5. The entropy withing the system will increase
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The second law of thermodynamic states that the entropy of an isolated system increases over time and remain constant for reversible process. 

Multiple choice physics heat engine: second law of thermodynamics second law of thermodynamics the second law of thermodynamics second law of thermodynamic

The second law of thermodynamics says that in a cyclic process

  1. Work cannot be converted into heat

  2. Heat cannot be converted into work

  3. Work cannot be completely converted into heat

  4. Heat cannot be completely converted into work
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Second law of thermodynamics states that in a cyclic process heat cannot be converted completely into work because attainment of $0K$ temperature is impossible.

Multiple choice physics heat engine: second law of thermodynamics second law of thermodynamics the second law of thermodynamics second law of thermodynamic

Which statement is true for second law of thermodynamics ?

  1. Heat can flow spontaneously from a cold object to a hot object.

  2. You can not create a heat engine which extracts heat and converts it all to useful work.

  3. According to Plank-Kelvin's law under some circumstances a perfect heat engine is possible.

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

The second law of thermodynamics states , that it is impossible to construct a heat engine , operating in cycle , which extracts heat and can convert it all to useful work .In other words , it is impossible for a heat engine to convert heat completely in work .

The efficiency of a heat engine is ,
            $\eta=1-\frac{Q _{2}}{Q _{1}}$
if $Q _{2}=0$ i.e. heat is not given to sink , it means total heat absorbed is converted into work , then
            $\eta=1$ , which is practically not possible .

Multiple choice physics heat engine: second law of thermodynamics second law of thermodynamics the second law of thermodynamics second law of thermodynamic

Which of the following laws of thermodynamics leads to the inference that it is difficult to convert whole of heat into work :

  1. zeroth

  2. second

  3. first

  4. third
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The second law of thermodynamics states that when energy change from one form to another form, entropy in a closed system increases.

In other words it can be stated as,
It is impossible to construct a device which produces no other effect than transfer of heat from lower temperature body to higher temperature body.
Hence it is clear that second law of thermodynamics leads to the interference that is difficult to convert whole of heat into work.

Multiple choice physics heat engine: second law of thermodynamics second law of thermodynamics the second law of thermodynamics second law of thermodynamic

The second law of thermodynamics implies : 

  1. whole of heat can be converted into mechanical energy

  2. no heat engine can be 100% efficient

  3. every heat engine has an efficiency of 100%

  4. a refrigerator can reduce the temperature to absolute zero
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

second law of thermodynamics states that ,

"It is impossible to construct a device which produces no other effect than transfer of heat from lower temperature body to higher temperature body."
$\therefore$ The second law of thermodynamics implies that no heat engine can be 100% efficient.

Multiple choice physics heat engine: second law of thermodynamics second law of thermodynamics the second law of thermodynamics second law of thermodynamic

Which statement is true about 2nd law of Thermodynamics?

  1. Heat can be converted to into work without changes in system or surroundings

  2. It is possible to construct a perpetual motion machine of second kind

  3. All spontaneous process are thermodynamically irreversible

  4. All spontaneous process are thermodynamically reversible
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 2nd law of Thermodynamics states that all spontaneous process are irreversible 

Multiple choice physics heat engine: second law of thermodynamics second law of thermodynamics the second law of thermodynamics second law of thermodynamic

Which is not true for Second Law of Thermodynamics?

  1. The second law of thermodynamics states that the total entropy of an isolated system always increases over time, or remains constant in ideal cases where the system is in a steady state or undergoing a reversible process.

  2. It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects.

  3. It is impossible to construct an engine which will work in a complete cycle, and produce no effect except the raising of a weight and cooling of a heat reservoir.

  4. The second law of thermodynamics states that the total energy of an isolated system is constant.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. The total entropy can remain constant in ideal cases where the system is in a steady state (equilibrium), or is undergoing a reversible process. In all spontaneous processes, the total entropy always increases and the process is irreversible. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past.

Historically, the second law was an empirical finding that was accepted as an axiom of thermodynamic theory. Statistical mechanics, classical or quantum, explains the microscopic origin of the law.
Hence option D is only incorrect option.
Multiple choice chemistry group 17 group 17 - physical properties physical properties of group 17 elements group 17 elements: the halogen family

Change in entropy is negative for:

  1. $Bromine (I) \rightarrow Bromine (g)$
  2. $C(s)+H _2O(g) \rightarrow CO(g)+H _2(g)$
  3. $N _2(g, 10 \ atm) \rightarrow N _2(g, 1 \ atm)$
  4. $Fe(at \ 400 \ K) \rightarrow Fe(at \ 300 \ K)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When $Br(I)$ goes to to $Br(g)$ then stability of molecules increase. This leads us to negative entropy.

Multiple choice botany plant water relation diffusion pressure deficit other pressure components osmosis in plants

Which of the following is not correct about $DPD$?

  1. Its the loss of diffusion pressure
  2. Maximum valu of $DPD$ is equal to $OP$
  3. $DPD$ of pure $H _{2}O$ is zero
  4. Increase in $TP$ of a cell decreases $DPD$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The term diffusion pressure deficit (DPD) is the reduction in the diffusion pressure of water in solution or cell over its pure state due to presence of solutes in it and forces opposing diffusion. Diffusion pressure of water is maximum and its theoretical value is 1236 atm. DPD of a solution is equal to its osmotic pressure i.e. DPD = OP(of solution). DPD of a cell is influence by both osmotic pressure and wall pressure (turgor pressure) which opposes the endosmotic entry of water, i.e. DPD = OP - Wall pressure. DPD is directly proportional to the concentration of the solution. DPD decreases with dilution of solution. The actual pressure with which cell absorbs water is called "suction pressure".

So the correct option is 'DPD of pure H$ _2$O is zero'.

Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

Which of the fallowing can enhance the rate of the reaction ?

  1. increasing the temperature

  2. increasing the concentration of products

  3. increasing the activation energy

  4. using a +Ve catalyst
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

Solution:- (A) increasing the temperature and (D) using a +ve catalyst
  • Temperature is a measure of the kinetic energy of a system, so higher temperature implies higher average kinetic energy of molecules and more collisions per unit time. Hence an increase in temperature is accompanied by an increase in the reaction rate. 
  • A higher concentration of reactants leads to more effective collisions per unit time, which leads to an increased reaction rate (except for zero order reactions). Similarly, a higher concentration of products tends to be associated with a lower reaction rate.
  • Catalysts (e.g., enzymes) lower the activation energy of a chemical reaction and increase the rate of a chemical reaction without being consumed in the process. 
  • Hence, using a positive catalyst and increasing the temperature, both can enhance the rate of reaction.

Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

What is the rate-determining step?

  1. The slowest step in the reaction.

  2. The fastest step in the reaction.

  3. The overall rate of the reaction.

  4. A law relating the steps of a reaction.

  5. The step which keeps on changing
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The slowest step in the mechanism of any reaction is the rate-determining step of the reaction.


Hence, the correct option is A.