How to Quickly Find out the Unit of a Reaction Rate Constant

A reaction rate constant/coefficient k is a proportionality constant which quantifies the rate and direction of a chemical reaction by relating it with the concentration of reactants in chemical kinetics.


The order of reaction is a number which quantifies the degree to which the rate of a chemical reaction depends on concentrations of the reactants.

In other words, the order of reaction is the exponent to which the concentration of a particular reactant is raised. For instance, the rate law can be expressed as: Rate = k [A]x [B]y where k = Rate constant, A & B are reactants and x & y are the orders of the reaction w.r.t. A & B respectively.

Mnemonic: The absolute value of the exponents of L & mol one less than the reaction order

Question:

What is the unit of the rate constant for a reaction that occurs between two second-order reactants?

Solution:


Click/tap to enlarge the image

For 2nd order, L1 mol─1 s─1 or M─1 s−1

For 1st order, L0 mol0 s─1 or s─1

For zero order, L─1 mol+1 s−1 or M s−1

Kaleidoscopic kinetics❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

(1)    Wikipedia Contributors. Rate equation. Wikipedia. https://en.wikipedia.org/wiki/Rate_equation.

(2)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

(3)    Ncert. Chemistry : Textbook for Class XII - Part.I; National Council Of Educational Research And Training: New Delhi.

Comments

Post a Comment

Popular posts from this blog

How to Predict where an Electrophilic Aromatic Substitution May Occur in a Ring – Part 3

Image
An organic reaction in which an atom attached to an aromatic system (usually hydrogen) is substituted by an electrophile is referred to as  electrophilic aromatic substitution  ( S E Ar  or  EAS ). One of the most important  EASs  is halogenation. If Bromine water is added to Aniline, a multi-substituted product ( 2,4,6 -derivative) is obtained as Aniline is a strongly activating group (the same happens to Phenol). To generate the mono-substituted product, a protection, say, an acyl group is required. Question: Predict the major product(s) of the following reaction: Click/tap to enlarge the image Solution infographic: Click/tap to enlarge the image Motivated by EAS ❓ Let Chemaficionado know  in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Electrophilic aromatic substitution . Wikipedia. https://en.wikipedia.org/wiki/Electrophilic_aromatic_substitution. (2)    ...
Read more

How to Carry out a Multistep Synthesis – Part 4

Image
Multistep synthesis  is the artificial execution of multiple organic chemical reactions to obtain one or more products by physical and chemical manipulations. Retrosynthetic analysis is a problem-solving approach in the organic syntheses, achieved by transforming a target molecule into simpler precursor structures regardless of any potential reactivity/interaction with reagents, and repeated until a simple or commercially available structure is reached, which can be used as a starting material to synthesize the target molecule. Question: How would you do the following transformation? Click/tap here to enlarge the image Solution infographic: Click/tap here to enlarge the image Let's keep in mind that any multistep synthesis is possible via several routes ❗Questions ❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Chemical synthesis . Wikipedia. https://en.wikipedia.org/wiki/Chemi...
Read more

How to Predict where an Electrophilic Aromatic Substitution May Occur in a Ring – Part 8

Image
An organic reaction in which an atom attached to an aromatic system (usually hydrogen) is substituted by an electrophile is referred to as  electrophilic aromatic substitution  ( S E Ar  or  EAS ). One of the most important  EASs  is nitration . Let's keep in mind that the presence of an activating group on the ring may complicate nitration. Question: Predict the major product(s) of the following reactions: Click/tap to enlarge the image Solution infographic: Click/tap to enlarge the image Eerie EAS chemistry❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Electrophilic aromatic substitution . Wikipedia. https://en.wikipedia.org/wiki/Electrophilic_aromatic_substitution. (2)      Brown, C.; Ford, M.  Higher Level Chemistry , 2nd ed.; Pearson Education: Harlow, Essex, 2014. ‌(3)     Electrophilic aromatic directing gro...
Read more