Correct Answer : Atoms break away from molecular structure
Explanation : At higher temperature molecules dissociate or ionize depending on the temperature range. Dissociation is a process where the atoms which are a part of the molecule break away from the molecular structure. This leads to the gas becoming highly chemically reactive.
Correct Answer : Temperature
Explanation : The vibrational motion of the molecules becomes significant by absorbing some of the energy that would otherwise go into the translational and rotational molecular motion as the temperature of a diatomic or polyatomic gas is raised above normal conditions. The excitation of vibrational energy, allows the specific heat to become a function of temperature function making it thermally perfect rather than calorically perfect.
Correct Answer : Oxygen is dissociated completely, nitrogen begins to dissociate
Explanation : Up to 2500 K, there is no reaction taking place and oxygen starts to dissociated. At 4000 K, oxygen gets completely dissociated and nitrogen begins the process of dissociation. The reaction is as follows :O2 → 2O
Correct Answer : 2
Explanation : For a diatomic molecule having translation energy, there are three thermal degrees of freedom. This energy is at the center of mass present due to the translation kinetic energy. The velocity components are in x, y, z direction of the Cartesian space.
Correct Answer : Fermions
Explanation : Molecules and atoms whose elementary particles present are in odd number usually follow a different statistical distribution known as Fermi – Dirac statistics. These atoms and molecules are commonly referred to as Fermions.
Correct Answer : Even number
Explanation : There are certain atoms and molecules which have even number (2, 4, 6, ..) of elementary particles (quarks, leptons) that obey Bose – Einstein statistical distribution. These particles are known as Bosons.
Correct Answer : Energy when gas is at absolute zero
Explanation : The molecule’s ground state refers to the energy that the molecule would have if the gas were theoretically at absolute zero temperature. Therefore, the values for the translational, rotational, vibrational, and electronic modes are often referred to as zero – point energies.
Correct Answer : Translation and electronic energy
Explanation : For a molecule, the total energy is a summation of rotational, translation, vibrational and electronic energy. But for a single atom, the total energy is a sum of only translation and electronic energy.
Explaination : CO2 is a linear polyatomic molecule that has similar properties as the diatomic molecule having rotational kinetic energy. The moment of inertia for the molecule in z – axis is negligible small compared to x and y – axis. Due to this reason, diatomic and even linear polyatomic molecules have only two thermal degrees of freedom.
Correct Answer : Distribution of molecules at different energy levels
Correct Answer : Temperature and volume
Explanation : The partition function Q is also known as the state sum. It is defined by the formula:This partition function has its use in statistical thermodynamics and is a function of both temperature and volume.
Correct Answer : Exponential
Explanation : On observing the equation of finding the molecule in a particular energy state as given by Boltzmann distribution law, we see that the graph varies exponentially as energy εj divided by kT (where k is the Boltzmann constant).
εj
kT
Correct Answer : False
Explanation : While analyzing the chemical composition of air at normal temperature and pressure, the major composition is of oxygen and nitrogen molecules. Presence of water vapor, argon, helium etc. are very less thus they can be neglected. Although, at higher temperature (2500K – 9000K), oxygen and nitrogen undergo chemical reaction and there is presence of O, N, NO, NO+ etc.
Correct Answer : Partial temperature
Explanation : There are several ways to describe the composition of air which is at a chemical equilibrium. These are – partial fraction, concentration, mole fraction, mole – mass fraction and mass fraction. These help in determining the composition of the reacting gas.
Correct Answer : Total pressure is equal to sum of partial pressures
Explanation : Dalton’s law of partial pressure was formulated to find out the total pressure of the chemically reactive mixture. This is the sum of partial pressures of individual components in the mixture. Dalton’s law is only applicable or perfect gases which means that the intermolecular forces between individual molecules is negligible.
Correct Answer : Reverse reaction
Explanation : The reaction quotient gives the same expression as the equilibrium constant for a reaction that is at chemical equilibrium. But, for a reaction when the reaction quotient (Q) is greater than the equilibrium constant (k), there’s more product than the reactant and reverse reaction takes place.
Correct Answer : No change in chemical composition spontaneously
Explanation : In a mixture of gases (air), when there is no sudden change in the chemical composition spontaneously or over a short period of time, the system is known to be in chemical equilibrium. There are no changes in temperature, velocity, pressure in the system.
Correct Answer : Kinetic energy between the molecules
Explanation : For a molecule to become vibrationally excited, it has to undergo several number of collisions which is affected by the kinetic energy present between these colliding particles. Higher kinetic energy results in higher gas temperature which eventually leads to lesser number of collisions required for the molecule to become vibrationally excited.
Correct Answer : High temperature, low pressure
Explanation : Molecular collision frequency is directly proportional to the pressure of the molecule and inversely proportional to the square root of the temperature. Therefore, for obtaining low collision frequency, the pressure should be low and the temperature should be high.
Correct Answer : Decreases
Explanation : The molecular collision frequency (Z) is given by the relation :Therefore, molecular collision frequency is inversely proportional to the square root of temperature which means that as the temperature increases, collision frequency decreases.
Correct Answer : Molecular collision frequency
Explanation : The amount of time taken by the molecules for collision depends on the molecular collision frequency. Thus parameter tells how many collisions take place with a neighboring particle in a second for a single particle.
Correct Answer : Less than 1
Explanation : Transition probability is the probability that a molecule will jump to another i + 1 level after the molecular collision. The transition of the molecule moving to a higher energy level requires several number of collisions. This probability value is always less than 1.
Correct Answer : Number of transitions per particle per second
Explanation : The collision frequency (Z) when multiplied with the transition probability (Pi, i + 1) yield the number of transitions per particle per second. Since the collision frequency is the number of collisions taking place per particle and the transition probability gives the number of transitions taking place per collision per particle.
(Pi, i + 1)
Correct Answer : Dissociative – recombination reaction of nitrogen and oxygen
Explanation : The reaction taking place below 9000 K for the formation of nitric oxide are dissociation reaction and bimolecular exchange reaction also known as shuffle reaction. They are as follows:
O2 + M ? 2O + M N2 + M ? 2N + M NO + M ? N + O + M O2 + N ? NO + O
