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 endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Select endothermic reaction:

  1. $S^{-}(g) + e^{-}(g) \rightarrow S^{2-}(g)$
  2. $Ne (g) + e^{-} (g) \rightarrow Ne^{-} (g)$
  3. $N(g) + e^{-} (g) \rightarrow N^{-}(g)$

  4. none of the above
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

The following are examples of endothermic reactions. They have a positive value of electron gain enthalpy and energy is absorbed when an electron is added to the atom.

$\displaystyle  Ne (g) + e^{-} (g) \rightarrow Ne^{-} (g)$

$\displaystyle N(g) + e^{-} (g) \rightarrow N^{-}(g)$

The following is an example of an exothermic reaction. They have a negative value of electron gain enthalpy and energy is released when an electron is added to the atom.

$\displaystyle S^{-}(g) + e^{-}(g) \rightarrow S^{2-}(g)$.

So, the correct options are $B$ and $C$

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Select the correct alternative.

Which of the following reactions are exothermic in nature?

  1. Combustion of Carbon

  2. Bond breaking

  3. Bond formation

  4. Both (a) and (c)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Combustion or burning is a high temperature exothermic redox chemical reaction between fuel and an oxidant oxygen. Bond breaking requires energy to be supplied for bond dissociation so it is an endothermic process while bond formation releases energy so that the product becomes stable which is an exothermic process.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

A chemical reaction in which energy is liberated is called:

  1. exothermic reaction

  2. endothermic reaction

  3. isothermal reaction

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

Exothermic Reaction: This is a chemical reaction that releases energy through light or heat.

$CH _4+2O _2\rightarrow CO _2+2H _2O+\triangle$
Burning of $CH _4$ gas its produces $CO _2$ and water vapour and releases heat.
Endothermic Reaction: This is a chemical reaction which requires or absorbs energy from its surroundings usually in the form of heat.
$N _2+O _2\rightarrow 2NO$
$\triangle0=+180.5$kg

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

One of the following is an exothermic reaction. This is:

  1. electrolysis of water.

  2. conversion of limestone into quicklime.

  3. process of respiration.

  4. process of photosynthesis.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

(A)In electrolysis of water heat energy is used to convert water into hydrogen and oxygen.

$2H _2O\rightarrow2H _2+O _2$
 it is an endothermic reaction.

(B)conversion of limestone into quicklime can be done by heating limestone.
$CaCO _3\rightarrow CaO+CO _2$ it is an endothermic reaction.


(C)During respiration breakdown of glucose in presence of oxygen releases energy, therefore it is an exothermic process.
$C _6H _{12}O _6+6O _2\rightarrow6H _2O+6CO _2+energy$

(D)In process of photosynthesis- light energy is used to convert carbon dioxide and water into glucose and oxygen
$6CO _2+6H _2O\rightarrow C _6H _{12}O _6+6O _2$

So the answer is (c)






.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

The formation of a larger chemical from the smaller components is known as 

  1. an endothermic reaction that requires energy

  2. an endothermic reaction that releases energy

  3. an exothermic reaction that requires energy

  4. an exothermic reaction that releases energy

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

The internal energy of a larger chemical is smaller than that of the constituent ones. Hence energy is liberated when smaller components combine to form a large molecule. Hence the process is exothermic.

The correct answer is option D.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Which is a reaction that absorbs energy?

  1. Exothermic

  2. Particle Size

  3. Endothermic

  4. Catalyst

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

The term endothermic process describes the process or reaction in which the system absorbs energy from its surroundings; usually, in the form of heat. The opposite of an endothermic process is an exothermic process, one that releases, "gives out" energy in the form of heat.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Which term means a reaction which releases energy?

  1. Exothermic

  2. Particle Size

  3. Endothermic

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

An exothermic reaction is a chemical reaction that releases energy by light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation: reactants → products + energy.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Chemical reactions occur with absorption of heat energy are called:

  1. precipitation reactions

  2. exothermic reactions

  3. endothermic reactions

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

The term endothermic process describes a process or reaction in which the system absorbs energy from its surroundings in the form of heat where in case of exothermic it releases energy to the surroundings. 

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

In endothermic reactions:

  1. reactants have more energy than products

  2. reactants have less energy than products

  3. reactants and products have same energy

  4. reactants have lower temperature than products
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An endothermic occurs if the products have a higher energy level than the reactants and $\Delta H$ will be positive. In other words, reactants have lesser energy than products.

In an exothermic reaction, the reacting mixture absorbs heat from the surroundings. Therefore, the reactants will have higher energy than the product here.

So the answer is option B.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Most of hydrolytic reactions are

  1. Exothermic

  2. Endothermic

  3. Irreversible

  4. Reversible
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Hydrolytic reactions are the reactions which involves breaking of the bond by the addition of water. It can be reversed by the condensation reaction where the joining of two molecule leads to release of water by formation of bonds. Saccharification is the reaction where the complex sugar molecule is broken into its component sugar molecules by hydrolysis. It can be reversed by condensation reaction.

So, the correct answer is option D.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

In a chemical reaction, the

  1. Rate depends on the value of $\triangle$G.

  2. Rate depends on the activation energy.

  3. Entropy change depends in the activation energy.
  4. Activation energy depends on the value of $\triangle$G.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
$\triangle$G describes change in free energy during occurrence of a chemical reaction. $\triangle$G can be calculated by the difference in free energy content of product and substrate. $\triangle$G value does not describes the rate of a reaction but only decides about the feasibility of a reaction. In case the free energy of product is less than the free energy of substrate the value of $\triangle$G will be negative and the reaction will be feasible but the rate at which it will be converted to product depends on a number of factors. The activation energy required for a reaction depends on the magnitude of $\triangle$G. For a feasible reaction, i.e., a reaction for which the free energy content of product is less than the free energy content of substrate, more the difference between free energy content of product and substrate, more negative will be $\triangle$G and lesser will be the activation energy required for completion of a reaction.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

In presence of an enzyme, the activation energy

  1. Increases

  2. Decreases

  3. First increases and then decreases

  4. Activation energy in not affected at all
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

There is an energy barrier between substrate and products, the energy required for alignment of reacting groups, formation of transient unstable charges, bond rearrangements, and other transformations required for the reaction to proceed. This is illustrated by the energy hill. The difference between the energy levels of the ground state and the transition state is the activation energy. The rate of a reaction reflects this activation energy : a higher activation energy corresponds to a slower reaction. Reaction rates can be increased by raising the temperature, thereby, increasing the number of molecules with sufficient energy to overcome the energy barrier. Alternatively, the activation energy can be lowered by adding a catalyst (enzyme). Catalysts enhance reaction rates by lowering activation energies.
Multiple choice physics energy and its forms idea of energy introduction to work and energy work and energy

The internal energy change when a system goes from state A to B is $40$ kJ/mole. If the system goes from A to B by a reversible path and returns to state A by an irreversible path what would be the net change in internal energy?

  1. $40$ kJ
  2. $> 40$ kJ
  3. $< 40$ kJ

  4. Zero
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
For a cyclic process the net change in the internal energy is zero because the change in internal energy doesnot depend on the path.

Multiple choice chemistry change around us physical changes changes and their classification physical changes

Which of them is not the characteristics of a physical change?

  1. Change in the physical properties

  2. New substances are formed

  3. Reversible reaction

  4. Original substance can be riveted back
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

1) A physical change is temporary and is usually reversible.
2) No new substances are formed during a physical change.
3) There is no change in mass of the substance during a physical change.
4) There is no net absorption or release of energy during a physical change.