# Order vs. Molecularity

The difference between Order and Molecularity is that the Order of a reaction is the algebraic sum of the powers to which the concentration of atoms is raised in a reaction, whereas Molecularity is the number of reactants taking part in an elementary reaction that is indicted by its chemical equation.

## Key Differences

Order of a reaction reduces as if a single reactant is found in excess in a reaction, while on the other hand, in case of molecularity, there is no such dependency on reactants.
Zero-order, first-order, and second-order reactions are classified based on order; however, based on molecularity, there are unimolecular reactions, bimolecular reactions, and trimolecular reactions.
Order of a reaction is the algebraic sum of the powers for the concentration of atoms in a reaction, whereas molecularity is just the number of reactants taking part in a chemical reaction.
There is no rate-determining step, and the overall reaction is used to calculate the order of a reaction; however, the rate-determining step is used to obtain the molecularity.
The order of a reaction is generally 1, 2, or 3 or can be zero or infraction or negative, but on the other hand, the Molecularity of a reaction can always be in a natural number.
Aimie Carlson
Jun 22, 2020
The rate order of a reaction can only be determined by experimenting, whereas, the molecularity of a reaction can be predicted based on its balancing equation.
The order of a reaction may vary whenever a reaction is subjected under changing pressure, temperature and concentration, etc., contrary to this, as molecularity is just several reactants that are taking part in a chemical reaction and are not affected by the external environment conditions.
Order of a reaction applies to simple and complex reactions or reactions that are completed in multi-steps both, whereas, molecularity is calculated for simple reactions only.
Aimie Carlson
Jun 22, 2020

## Comparison Chart

### .

The algebraic sum of the powers to which the concentration of atoms is raised in a reaction
The number of reactants taking part in a chemical reaction

### Determination

Can only be determined by experimenting
No complicated experimentation is required

### Dependence

Order of a reaction reduces if a single reactant is in excess
Molecularity does not depend on the excessiveness of a reactant.

### Value

Order of a reaction is generally 1, 2 or 3 or maybe zero or in fraction or negative
Molecularity of a reaction can always be in a natural number
Aimie Carlson
Jun 22, 2020

### Rate Determining Step

No rate-determining step and the overall reaction is used to calculate the order of a reaction
The rate-determining step is used to obtain the molecularity
Janet White
Jun 22, 2020

### Effect of the External Environment

The order of a reaction may vary whenever a reaction is subjected to changing pressure, temperature, and concentration, etc.
Molecularity of a reaction is invariant to these changes in the atmosphere.
Harlon Moss
Jun 22, 2020

### Classification of Reactions

Reactions are classified based on their order as · Zero-Order Reaction · 1st Order Reaction · 2nd Order Reaction
Reactions are classified based on their molecularity as · Unimolecular Reaction · Bimolecular Reaction · Trimolecular Reaction
Aimie Carlson
Jun 22, 2020

### Application

Order of a reaction applies to a simple and elementary reaction
Molecularity is calculated for simple reactions only there is no sign of calculating molecularity of a complex reaction

## Order and Molecularity Definitions

#### Order

A condition of logical or comprehensible arrangement among the separate elements of a group.

#### Molecularity

Of, relating to, or consisting of molecules.

#### Order

A condition of methodical or prescribed arrangement among component parts such that proper functioning or appearance is achieved
Checked to see that the shipping department was in order.

#### Molecularity

Of or relating to simple or basic structure or form.

#### Order

Condition or state in general
The escalator is in good working order.

#### Molecularity

(uncountable) The state of being molecular

#### Order

The established system of social organization
"Every revolution exaggerates the evils of the old order" (C. Wright Mills).

#### Molecularity

(chemistry) (of a reaction) The number or molecules that react directly with one another

#### Order

A condition in which freedom from disorder or disruption is maintained through respect for established authority
Finally restored order in the rebellious provinces.

#### Molecularity

The state of consisting of molecules; the state or quality of being molecular.

#### Order

A sequence or arrangement of successive things
Changed the order of the files.

#### Order

The prescribed form or customary procedure, as in a meeting or court of law
The bailiff called the court to order.

#### Order

An authoritative indication to be obeyed; a command or direction.

#### Order

A command given by a superior military officer requiring obedience, as in the execution of a task.

#### Order

Orders Formal written instructions to report for military duty at a specified time and place.

#### Order

A commission or instruction to buy, sell, or supply something.

#### Order

That which is supplied, bought, or sold.

#### Order

A request made by a customer at a restaurant for a portion of food.

#### Order

The food requested.

#### Order

(Law) A directive or command of a court.

#### Order

Any of several grades of the Christian ministry
The order of priesthood.

#### Order

Often orders The rank of an ordained Christian minister or priest.

#### Order

Often orders The sacrament or rite of ordination.

#### Order

Any of the nine grades or choirs of angels.

#### Order

A group of persons living under a religious rule
Order of Saint Benedict.

#### Order

An organization of people united by a common fraternal bond or social aim.

#### Order

A group of people upon whom a government or sovereign has formally conferred honor for unusual service or merit, entitling them to wear a special insignia
The Order of the Garter.

#### Order

The insignia worn by such people.

#### Order

Often orders A social class
The lower orders.

#### Order

A class defined by the common attributes of its members; a kind.

#### Order

Degree of quality or importance; rank
Poetry of a high order.

#### Order

Any of several styles of classical architecture characterized by the type of column and entablature employed. Of the five generally accepted classical orders, the Doric, Ionic, and Corinthian orders are Greek and the Tuscan and Composite orders are Roman.

#### Order

A style of building
A cathedral of the Gothic order.

#### Order

(Biology) A taxonomic category of organisms ranking above a family and below a class.

#### Order

The sum of the exponents to which the variables in a term are raised; degree.

#### Order

An indicated number of successive differentiations to be performed.

#### Order

The number of elements in a finite group.

#### Order

The number of rows or columns in a determinant or matrix.

#### Order

To issue a command or instruction to
Ordered the sailors to stow their gear.

#### Order

To direct to proceed as specified
Ordered the intruders off the property.

#### Order

To give a command or instruction for
The judge ordered a recount of the ballots.

#### Order

To request to be supplied with
Order eggs and bacon for breakfast.

#### Order

To put into a methodical, systematic arrangement
Ordered the books on the shelf.

#### Order

To predestine; ordain.

#### Order

To give an order or orders; request that something be done or supplied.

#### Order

(countable) Arrangement, disposition, or sequence.
Put the children in age order
It's arranged in order of frequency

#### Order

(countable) A position in an arrangement, disposition, or sequence.

#### Order

(uncountable) The state of being well arranged.
The house is in order; the machinery is out of order.

#### Order

(countable) Conformity with law or decorum; freedom from disturbance; general tranquillity; public quiet.
To preserve order in a community or an assembly
Order in the court!

#### Order

(countable) A command.
Give an order

#### Order

(countable) A request for some product or service; a commission to purchase, sell, or supply goods.
Make an order
Receive an online order for the new range of sunglasses

#### Order

(countable) A group of religious adherents, especially monks or nuns, set apart within their religion by adherence to a particular rule or set of principles.
St. Ignatius Loyola founded the Jesuit order in 1537.

#### Order

(countable) An association of knights.
The Order of the Garter, the Order of the Bath.

#### Order

Any group of people with common interests.

#### Order

(countable) A decoration, awarded by a government, a dynastic house, or a religious body to an individual, usually for distinguished service to a nation or to humanity.

#### Order

A category in the classification of organisms, ranking below class and above family; a taxon at that rank.
The magnolia and nutmeg families belong to the order Magnoliales.

#### Order

A number of things or persons arranged in a fixed or suitable place, or relative position; a rank; a row; a grade; especially, a rank or class in society; a distinct character, kind, or sort.
The higher or lower orders of society
Talent of a high order

#### Order

(Christianity) An ecclesiastical rank or position, usually for the sake of ministry, when plural holy orders.
There have been many major and minor orders in the history of Christianity: the order of virgins, of deacons, priests, lectors, acolytes, porters, catechists, widows, etc.
To take orders or holy orders means to be ordained a deacon or priest

#### Order

(architecture) The disposition of a column and its component parts, and of the entablature resting upon it, in classical architecture; hence (since the column and entablature are the characteristic features of classical architecture) a style or manner of architectural design.

#### Order

(cricket) The sequence in which a side’s batsmen bat; the batting order.

#### Order

(electronics) A power of polynomial function in an electronic circuit’s block, such as a filter, an amplifier, etc.
A 3-stage cascade of a 2nd-order bandpass Butterworth filter

#### Order

(chemistry) The overall power of the rate law of a chemical reaction, expressed as a polynomial function of concentrations of reactants and products.

#### Order

(set theory) The cardinality, or number of elements in a set, group, or other structure regardable as a set.

#### Order

For given group G and element g ∈ G, the smallest positive natural number n, if it exists, such that (using multiplicative notation), gn = e, where e is the identity element of G; if no such number exists, the element is said to be of infinite order (or sometimes zero order).

#### Order

(graph theory) The number of vertices in a graph.

#### Order

(order theory) A partially ordered set.

#### Order

(order theory) The relation on a partially ordered set that determines that it is, in fact, a partially ordered set.

#### Order

(algebra) The sum of the exponents on the variables in a monomial, or the highest such among all monomials in a polynomial.
A quadratic polynomial, $a x^2 + b x + c,$ is said to be of order (or degree) 2.

#### Order

(finance) A written direction to furnish someone with money or property; compare money order, postal order.

#### Order

(transitive) To set in some sort of order.
We need to order them alphabetically.

#### Order

(transitive) To arrange, set in proper order.
The books in the shelf need ordering.

#### Order

(transitive) To issue a command to.
He ordered me to leave.
I hate being ordered around by my co-workers.

#### Order

(transitive) To request some product or service; to secure by placing an order.
You can now order most products to be delivered to your home.
To order groceries
To order food from a restaurant

#### Order

To admit to holy orders; to ordain; to receive into the ranks of the ministry.

#### Order

Regular arrangement; any methodical or established succession or harmonious relation; method; system
The side chambers were . . . thirty in order.
Bright-harnessed angels sit in order serviceable.
Good order is the foundation of all good things.

#### Order

Right arrangement; a normal, correct, or fit condition; as, the house is in order; the machinery is out of order.

#### Order

The customary mode of procedure; established system, as in the conduct of debates or the transaction of business; usage; custom; fashion.
And, pregnant with his grander thought,Brought the old order into doubt.

#### Order

Conformity with law or decorum; freedom from disturbance; general tranquillity; public quiet; as, to preserve order in a community or an assembly.

#### Order

That which prescribes a method of procedure; a rule or regulation made by competent authority; as, the rules and orders of the senate.
The church hath authority to establish that for an order at one time which at another time it may abolish.

#### Order

A command; a mandate; a precept; a direction.
Upon this new fright, an order was made by both houses for disarming all the papists in England.

#### Order

Hence: A commission to purchase, sell, or supply goods; a direction, in writing, to pay money, to furnish supplies, to admit to a building, a place of entertainment, or the like; as, orders for blankets are large.
In those days were pit orders - beshrew the uncomfortable manager who abolished them.

#### Order

A number of things or persons arranged in a fixed or suitable place, or relative position; a rank; a row; a grade; especially, a rank or class in society; a group or division of men in the same social or other position; also, a distinct character, kind, or sort; as, the higher or lower orders of society; talent of a high order.
They are in equal order to their several ends.
Various orders various ensigns bear.
Which, to his order of mind, must have seemed little short of crime.

#### Order

A body of persons having some common honorary distinction or rule of obligation; esp., a body of religious persons or aggregate of convents living under a common rule; as, the Order of the Bath; the Franciscan order.
Find a barefoot brother out,One of our order, to associate me.
The venerable order of the Knights Templars.

#### Order

An ecclesiastical grade or rank, as of deacon, priest, or bishop; the office of the Christian ministry; - often used in the plural; as, to take orders, or to take holy orders, that is, to enter some grade of the ministry.

#### Order

The disposition of a column and its component parts, and of the entablature resting upon it, in classical architecture; hence (as the column and entablature are the characteristic features of classical architecture) a style or manner of architectural designing.

#### Order

An assemblage of genera having certain important characters in common; as, the Carnivora and Insectivora are orders of Mammalia.

#### Order

The placing of words and members in a sentence in such a manner as to contribute to force and beauty or clearness of expression.

#### Order

Rank; degree; thus, the order of a curve or surface is the same as the degree of its equation.
Whiles I take order for mine own affairs.

#### Order

To put in order; to reduce to a methodical arrangement; to arrange in a series, or with reference to an end. Hence, to regulate; to dispose; to direct; to rule.
To him that ordereth his conversation aright.
Warriors old with ordered spear and shield.

#### Order

To give an order to; to command; as, to order troops to advance.

#### Order

To give an order for; to secure by an order; as, to order a carriage; to order groceries.

#### Order

To admit to holy orders; to ordain; to receive into the ranks of the ministry.
These ordered folk be especially titled to God.
Persons presented to be ordered deacons.

#### Order

To give orders; to issue commands.

#### Order

(often plural) a command given by a superior (e.g., a military or law enforcement officer) that must be obeyed;
The British ships dropped anchor and waited for orders from London

#### Order

A degree in a continuum of size or quantity;
It was on the order of a mile
An explosion of a low order of magnitude

#### Order

Established customary state (especially of society);
Order ruled in the streets
Law and order

#### Order

Logical or comprehensible arrangement of separate elements;
We shall consider these questions in the inverse order of their presentation

#### Order

A condition of regular or proper arrangement;
He put his desk in order
The machine is now in working order

#### Order

A legally binding command or decision entered on the court record (as if issued by a court or judge);
A friend in New Mexico said that the order caused no trouble out there

#### Order

A commercial document used to request someone to supply something in return for payment and providing specifications and quantities;
IBM received an order for a hundred computers

#### Order

A formal association of people with similar interests;
He joined a golf club
They formed a small lunch society
Men from the fraternal order will staff the soup kitchen today

#### Order

A body of rules followed by an assembly

#### Order

(usually plural) the status or rank or office of a Christian clergyman in an ecclesiastical hierarchy;
Theologians still disagree over whether `bishop' should or should not be a separate order

#### Order

A group of person living under a religious rule;
The order of Saint Benedict

#### Order

(biology) taxonomic group containing one or more families

#### Order

A request for food or refreshment (as served in a restaurant or bar etc.);
I gave the waiter my order

#### Order

(architecture) one of original three styles of Greek architecture distinguished by the type of column and entablature used or a style developed from the original three by the Romans

#### Order

Putting in order;
There were mistakes in the ordering of items on the list

#### Order

Give instructions to or direct somebody to do something with authority;
I said to him to go home
She ordered him to do the shopping
The mother told the child to get dressed

#### Order

Make a request for something;
Order me some flowers
Order a work stoppage

#### Order

Issue commands or orders for

#### Order

Bring into conformity with rules or principles or usage; impose regulations;
We cannot regulate the way people dress
This town likes to regulate

#### Order

Bring order to or into;
Order these files

#### Order

Place in a certain order;
Order these files

#### Order

Appoint to a clerical posts;
He was ordained in the Church

#### Order

Arrange thoughts, ideas, temporal events, etc.;
Arrange my schedule
Set up one's life
I put these memories with those of bygone times

#### Order

Assign a rank or rating to;
How would you rank these students?
The restaurant is rated highly in the food guide

### Order vs. Molecularity

Order of a reaction is the algebraic sum of the powers to which the concentration of atoms is raised in a reaction, while on the other hand, molecularity is the number of reactants taking part in a chemical reaction that is indicted by its chemical equation. Order of a reaction reduces a single reactant is in excess in a reaction, while on the other hand, in case of molecularity, there is no such dependency on reactants.

The order of a reaction is generally 1, 2, or 3 or maybe zero or in a fraction or negative, but on the flip side, the molecularity of a reaction can always be in a natural number. Order of a reaction can only be determined by experimenting and cannot be predicted based on the balanced chemical equation, whereas the molecularity of a reaction can easily be predicted based on its balancing equation, and no complicated experimentation is required.

The order of a reaction may vary whenever a reaction is subjected under changing pressure, temperature, and concentration, etc., contrary to this, as molecularity, is just several reactants that are taking part in a chemical reaction which makes it irrelevant to these changes in the atmosphere and makes it invariant. For calculating the order of a reaction, there is no rate-determining step, and the overall reaction is used to calculate the order of a reaction; however, the rate-determining step is used to obtain the molecularity, and the overall reaction is not required.

There are Zero-order, first-order, and second-order reactions that are classified based on order; however, based on molecularity, there are unimolecular reactions, bimolecular reactions, and trimolecular reactions. Order of a reaction applies to simple and elementary reactions both, whereas, molecularity is calculated for simple reactions only, there is no sign of calculating the molecularity of a complex reaction.

### What is Order?

The rate order of a reaction is defined as the algebraic sum of the powers to which the concentration of atoms is raised in a reaction. It is also referred to as the power dependence of the rate of each reactant during the reaction. It is the sum of exponents of the rate law derived, and it may not depend on the stoichiometric coefficients of each reactant. Due to this reason, the rate of law is determined experimentally.

It is a quantitative measure regarding the rate of a reaction. The rate law is the equation raised. The order of a reaction is generally 1, 2, or 3 or maybe zero or in fraction or negative. The rate order of a reaction can only be resolute by experimenting and usually cannot be expected based on the balanced chemical equation. In an example like X + Y + Z → A + B + C, the rate law will be concluded as R = k [X] p [Y] q [Z] r .

Where R is the short form for the rate of reaction, X, Y, and Z are reactants, p, q, and r are orders of the reaction for X, Y, and Z. K here is considered as proportionality constant, and it mirrors the character of the reaction. Chemists discuss the sum of p, q, and r as the kinetic direction of the reaction. The order of these values is calculated experimentally.

The order of this reaction will be calculated by considering the overall reaction, unlike in molecularity, where rate-determining steps determine the molecularity. There are several types of reactions based on their order. There are Zero-order reactions in which the rate of a reaction does not rest on the concentration of reactants. First-order reactions are those who are reliant on the deliberation of reactants and correspond to a uni-molecular reaction. A one-second order reactant or two first order reactants are the second-order reactions that may hang on the deliberation of these two orders.

The order of a reaction may vary whenever a reaction is subjected to changing pressure, temperature, and concentration, etc. For calculating the order of a reaction, there is no rate-determining step, and the overall reaction is used to calculate the order of a reaction, and the order of a reaction applies to simple and elementary reactions both.

### What is Molecularity?

Molecularity is the number of reactants participating in a chemical reaction that is indicted by its chemical equation. In the case of Molecularity, there is no dependency on the excessiveness of reactants as it was in the order of reactions. Molecularity of a reaction can always be in a natural number as it is the number of reactants in a particular reaction.

Molecularity of a reaction can easily be predicted based on its balancing equation, and no complicated experimentation is required. It does not depend upon the external environment as it is just a quantity of reactants that are taking part in a chemical reaction, which makes it irrelevant to these changes in the atmosphere and makes it invariant. The rate-determining step is used to obtain the molecularity, and the overall reaction is not required.

Based on molecularity, there are unimolecular reactions, bimolecular reactions, and trimolecular reactions. In unimolecular reactions, a single molecule undergoes amendments while reaction proceeds, and it has only one reactant and a single rate-determining step. In bimolecular reactions, two reactants are involved and are completing the reaction. However, in trimolecular reactions, three reactants are involved in the rate-determining step. Molecularity is just calculated for simple reactions; only there is no sign of calculating the molecularity of a complex or multi-step reaction.