Chemistry · Physics

Thermodynamics and Chemical Kinetics

1,092 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

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.

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

In a physical change :

  1. new substances are not formed

  2. reaction is reversible

  3. change is temporary

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

Physical changes in a substance do not form new substances, these reactions are reversible and the change is temporary.

Physical changes are the changes affecting the form of a chemical substance, but not its chemical composition. They are used to separate mixtures into their component compounds, but cannot usually be used to separate compounds into chemical elements or simpler compounds.

Multiple choice chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

A chemical equation is balanced according to the law of: 

  1. multiple proportions

  2. constant proportions

  3. reciprocal proportions

  4. conservation of mass
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
When we balance an equation, we determine the ratio of reactants to products which allows for the total number of atoms of reactants to match the number of atoms of the products.

 Since the type of atoms does not change and the number of atoms stays that same, the total mass that goes into the chemical change will match the mass that comes out after the change.

   So, law of conservation of mass is the correct answer.
Multiple choice physics the essence of change forms of energy and energy conservation energy for everything forms of energy

The energy present in petrol is :

  1. Chemical

  2. Kinetic

  3. Potential

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

 chemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction to transform other chemical substances.

kinetic energy is due to motion.
potential energy is due to relative position.
heat energy is due to temperature.
in petrol different different reaction occurs which provide energy to run the engine, so energy possessed in petrol is chemical energy.
option A.

Multiple choice physics the essence of change forms of energy and energy conservation energy for everything forms of energy

What is potential energy?

  1. Energy of an abject due to its position or arrangement in a system

  2. Energy of an abject due to its nature or arrangement in a system

  3. Energy of an abject due to its shape or arrangement in a system

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

Energy of an abject due to its position or arrangement in a system is potential energy. 

Multiple choice physics the essence of change forms of energy and energy conservation energy for everything forms of energy

Identify, which of the following energies can be positive only:

  1. Kinetic energy

  2. Potential energy

  3. Mechanical energy

  4. Both kinetic and mechanical energies.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Potential energy is the energy stored by the virtue of the position of a body.While,kinetic energy is the energy possessed by the virtue of motion.
Hence, K.E is always +ve .
When a body is raised to a particular height,work is done against the force of gravity and P.E is $ - $ve.
When the body is falling freely the work is done in the direction of force of gravity and P.E is $+$ ve.