Chemical Kinetics Test - 12

As the pressure increases collision frequency increases.

Vice versa pressure is decreased to half, frequency of collision decreases to half.

Therefore, its value at 0.5 atm will be Z.

Hence, the correct option is (D).

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.

Hence, the correct option is (A).

The reaction rate (rate of reaction) or speed of reaction for a reactant or product in a particular reaction is intuitively defined as how fast or slow a reaction takes place. For example, the oxidative rusting of iron under Earth's atmosphere is a slow reaction that can take many years.

Hence, the correct option is (B).

VSEPR theory is not related to the chemical kinetics.

Valence shell electron pair repulsion (VSEPR) theory is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. The VSEPR theory is used to predict the shape of the molecules from the electron pairs that surround the central atoms of the molecule

Hence, the correct option is (B).

The rate constant has a unit for a different order of a reaction.

The rate constant, or the specific rate constant, is the proportionality constant in the equation that expresses the relationship between the rate of a chemical reaction and the concentrations of the reacting substances.

The stoichiometry of the reaction is indicated by placing stoichiometric coefficients before the chemical species. These are usually integer numbers, but in some bioenergetic processes, non-integer stoichiometries are known to pertain.

Thus, the statement i, ii, iii is correct.

Hence, the correct option is (A).

Activation energy, is the minimum amount of energy that is required to activate atoms or molecules to a condition in which they can undergo chemical transformation or physical transport. In terms of the transition-state theory, the activation energy is the difference in energy content between atoms or molecules in an activated or transition-state configuration and the corresponding atoms and molecules in their initial configuration.

Hence, the correct option is (C).

The rate of a chemical reaction depends on the nature of reactants because the number of bonds broken in the reactant molecules and the number of bonds formed in product molecules changes.

In other words, the ease with which bonds are formed and the ease with which bonds are broken determines the rate of the chemical reaction.

Hence, the correct option is (A).

Collision diameter will be least for the low molecular weight.

d α \(\frac{1}{​M}\)

In this case, CO₂ has the highest molecular weight.

Hence, the correct option is (C).

\(50 \%\) reaction completes in 2 hours. That is, half life of reaction is 2 hours

\(t _{\left(\frac{1}{2}\right)}=2\) hours. Also given that, \(t _{\left(\frac{3}{4}\right)}=4\) hours

We can observe that,

\(t _{\left(\frac{3}{4}\right)}=2 \times t _{\left(\frac{1}{2}\right)}\)

Thus, relation holds true only in first order

Hence, the correct option is (A).

The study of chemical kinetics becomes highly complicate if there occurs side reactions or surface reactions. These reactions bring changes in the value of rate constant and not help to proceeds the reaction in the right manner.

Hence, the correct option is (C).

A reaction has both ΔH and ΔS negative. The rate of reaction increases with increase of temperature.

There is no relation between spontaneity and rate of reaction as rate of reaction is the measure of how fast is the product formed and spontaneity refers whether the reaction occurs with  release of free energy which is set at the specified temperature.

Spontaneity has no connection with speed of the reaction taking place. Although, in order to increase the rate of the reaction the temperature should be increased as it provides activation energy to the molecule for collision.

Hence, the correct option is (A).

According to the given reaction, Rate = k [A]² [B]¹

When A becomes 3A i.e., triples, the rate will become: Rate = k [3A]² [B]¹ = 9k [A]² [B]

Thus, rate of reaction is increased by 9 times.

Hence, the correct option is (B).

Rate of reaction depends on temperature, concentration of the reactants and presence of catalyst.

Example:

1. At higher temperature, particles collide more frequently and with greater similarity.

2. \(CH _{4}( g )+2 O _{2}( g ) \longrightarrow CO _{2}( g )+2 H _{2} O\) Faster rate

\(C _{25} H _{52}( g )+38 O _{2} \longrightarrow 25 CO _{2}( g )+26 H _{2} O\) Slow rate

So, reaction depends on nature of reactants.

3. A catalyst is a species that speeds up a chemical reaction with being chemically changed upon completion of reaction.

Hence, the correct option is (D).

If the product concentration is \(x\), then:

For a zero-order reaction \(\frac{ x }{ t }= k\)

Thus, the graph would be a straight line passing through the origin. So the given information is for zero order reaction. for zero order reaction, the rate of reaction is constant. Thus, the plot of rate vs time ie., \(-\frac{ d [ X ]}{ dt }\) vs time will be a straight line parallel to the \(x\)-axis.

Hence, the correct option is (C).

Chemical kinetics is branch of physical chemistry that is concerned with understanding the rates of chemical reactions.

Structures and physical changes are deal in solid state and while studying liquids. Thermochemistry deals with energy changes in chemical reactions.

Hence, the correct option is (D).

The rate of a chemical reaction is the change in concentration over the change in time and is a metric of the "speed" at which a chemical reactions occurs and can be defined in terms of two observables:

1. The Rate of Disappearance of Reactants: \(\frac{[-\Delta \text { Reactants] }}{\Delta \text { time }}\)

2. The Rate of Formation of Products: \(\frac{[\Delta \text { Products }]}{\Delta \text { time }}\)

Thus, the units for the rate is Molarity per Seconds \(\left(\frac{M}{s}\right)\). or Moles per litre per second \(\left(\right.\)moles \(\left.{ }^{-1} s ^{-1}\right)\).

Hence, the correct option is (B).

In autocatalysis, a reaction product is itself a catalyst for that reaction leading to positive feedback.

A single chemical reaction is said to have undergone autocatalysis, or be autocatalytic, if one of the reaction products is also a reactant and therefore a catalyst in the same or a coupled reaction. The reaction is called an autocatalytic reaction. A catalyst is a substance that accelerates the rate of a chemical reaction but remains chemically unchanged afterwards.

Hence, the correct option is (A).

The quenching of a reaction can be made by cooling as well as diluting the reaction mixture. The reaction is supposed to be completed if it is kept for a long time or strongly heated. Quenching a reaction is used to deactivate any unreacted reagents. It is also done by adding an antisolvent to induce precipitation, and collecting or removing the solids.

Hence, the correct option is (D).

The rate of chemical reaction is directly proportional to the equilibrium constant.

∴ For K = 10³, the reaction will complete fastest among all the given options, because it is the only option which is having the highest value of equilibrium constant.

Hence, the correct option is (C).

The most molecular collision are in between 2 molecules.

The collision theory is based on the assumption that for a reaction to occur it is necessary for the reacting species to come together or collide with one another. Collision theory states that when suitable particles of the reactant hit each other, only a certain amount of collisions result in a perceptible or notable change, these successful changes are called successful collisions.

Hence, the correct option is (A).

Higher order (>3) reactions are rare due to low probability of simultaneous collision of all the reacting species.

For higher order (>3) reactions to occur, 3 or more molecules (having energy equal to or greater than activation energy) must simultaneously collide with proper orientation.

The probability for such collisions is very low. Thus, these reactions are rare.

Hence, the correct option is (A).

For a reaction to occur, reactant molecules must collide with each other. Only those collisions result in product formation which has energy equal to or more than certain minimum energy. This energy is called the threshold energy. This implies an energy barrier between reactants and products that must be crossed before products can be formed.

The energy required for crossing the energy barrier comes from the kinetic energy of reacting molecules. Hence, the minimum extra energy over and above the average potential energy of the reactants, which must be supplied so that the reactants can cross over the energy barrier is called the activation energy (AE).

Activation energy = (Threshold energy) - (Internal energy of the reactants)

AE = TE - IE

or TE = AE + IE

Hence, the correct option is (B).

The higher the temperature higher the energy.

Usually conducting a reaction at a higher temperature delivers more energy into the system and increases the reaction rate by causing more collisions between particles, as explained by collision theory. However, the main reason that temperature increases the rate of reaction is that more of the colliding particles will have the necessary activation energy resulting in more successful collisions (when bonds are formed between reactants).

Hence, the correct option is (B).

Increasing the temperature of the substance, increases the fraction of molecules which collide with energies greater than Ea. For every 10\(^{\circ}\)C rise in temperature, the fraction of molecules having energy equal to or greater than Ea gets doubled leading to doubling the rate of reaction.

Thus, the number of fruitful collisions gets doubled.

Hence, the correct option is (D).

The oxidative rusting of iron under Earth's atmosphere is slow reaction.

The reaction rate (rate of reaction) or speed of reaction for a reactant or product in a particular reaction is intuitively defined as how fast or slow a reaction takes place. For example, the oxidative rusting of iron under Earth's atmosphere is a slow reaction that can take many years.

Hence, the correct option is (B).

The rate for the reaction between ionic compounds cannot be determined because they are generally instantaneous reactions.

Ionic compounds readily dissociate into ions, which react with each other instantaneously to form products. Therefore the rate of these reactions cannot be determined.

Hence, the correct option is (C).

For producing the effective collisions, the colliding molecules must posses bimolecular reactions.

Bimolecular reaction originates from a collision between two reactants. Whether or not a collision results in a chemical reaction is determined by the energy of the reactants and their orientation.

The total energy of the two reactants must be in excess of the activation energy (Ea), and the reactants must be in a favorable orientation for the chemical reaction to occur. While there are many different orientations possible for the collisions, usually not all of them will result in a chemical reaction. For most reactions, if the orientation is not correct, the reactants will bounce off of each other without a chemical reaction.

Hence, the correct option is (C).

As the temperature rises, more collisions start taking place which results in an increase in rate of the chemical reaction.

With rise in temperature, fraction of molecules possessing kinetic energy greater than the activation energy increases. Only such molecules are able to cause effective collisions and result in the formation of product. Thus, as the fraction of such molecules increases, rate of the reaction increases.

Hence, the correct option is (D).

The exponential factor represents the fraction of "reactants" that have approached the activation energy hill and made it over per number of attempts.

The exponential factor reflects the percentage of reactants who have approached and crossed the activation energy hill in the number of tries.

Hence, the correct option is (C).

The rate of a zero order reaction is independent of the concentration of the reactants. The reaction proceeds at a constant rate throughout.

In some reactions, the rate is apparently independent of the reactant concentration. The rates of these zero order reactions do not vary with increasing nor decreasing reactants concentrations. This means that the rate of the reaction is equal to the rate constant.

Hence, the correct option is (B).