MAHE Manipal B.Sc Nursing 2025
ApplyAccorded Institution of Eminence by MoE, Govt. of India | NAAC A++ Grade | Ranked #4 India by NIRF 2024
Chemical Kinetics is one of the important chapters of class 12 Chemistry. It generally deals with understanding the rate of chemical reactions. Rate of chemical reaction is the speed at which chemical reaction takes place. Reaction rate is influenced by many factors including temperature, pressure, catalyst etc.
NEET 2025: Biology: Mind Maps & Important Diagrams | Mock Test (Free)
NEET 2025: Syllabus | Most Scoring concepts | NEET PYQ's (2015-24)
New: Meet Careers360 experts in your city and get guidance on shortlisting colleges
New Programme: B.E. Environmental & Sustainability @ BITS Pilani for PCB Candidates
Reactions are classified in various orders like zero order reaction, First order reaction, second order reaction among others on the basis of rate law followed by them.
A first-order reaction refers to the reaction in which the rate of reaction is proportional to the first power of concentration of the reactant at any point of time. Hence, higher the concentration of reactant, higher will be the rate of reaction. Rate of first order reaction decreases as it proceeds due to decrease in concentration of reactant.
Hence in first order reaction, rate of reaction is directly proportional to the concentration of reactant as described in the equation below.
Reaction-
Reactant →Product
Rate =k[Reactant]
Below are some of the examples of First Order reaction
2N2O5 → 4NO2+O2
Rate = k[N2O5]
2H2O2 → 2H2O + O2
Rate = k[H2O2]
After analysing the last five years of NEET papers, it has been observed that, total 10 questions were asked from the Chemical Kinetics Chapter and out of those, four questions belong to First order reaction. This shows that First order reaction is the most important concept of Chemical Kinetics and most of the questions can be solved if Integral form of first order reaction is understood well. Questions asked from first order reactions are discussed in the article below.
Differential Rate Law for a First-Order Reaction reflects the change in concentration with respect to time which is shown by equation below:
Let us assume a first order reaction: A(Reactant)→B(Product)
Rate = -d[A]/dt = k[A]1 = k[A]
In the above equation,
‘k’ represents the rate constant of the first-order reaction, the unit of the rate constant is s-1.
‘[A]’ represents the concentration of the reactant.
d[A]/dt represents the change in the concentration of reactant ‘A’ with respect to time.
Integrated Rate Law of first order reaction is used to calculate the value of rate of rate constant, concentration of reactant a given time, half life etc. Most of the numericals are solved by using Integrated rate law only. Differential rate law is used to obtain the Integral rate law of a First order reaction.
Differential rate law is: -d[A]/dt = k[A]
d[A]/dt = -k[A]
Integrating both sides, we get
Where [A]o is concentration of reactant at time t0 s, and [A] is the concentration of reactant at time t. We get,
Considering t0 =0, and solving the equation, we get
ln[A] – ln[A]0 = -kt
ln[A] =ln[A]0 -kt
Raising each side to component e, we get
Hence, is the final expression in the integrated form for first order reaction. The above derivation is useful in solving many numerical problems.
Using the Integrated Rate law, Concentration v/s time Graph for First order reaction can be obtained which is shown below
As the first-order reaction follows the equation ln[A] = ln[A]0 – kt which is similar to that of a straight line (y = mx + c) with slope -k. Hence, this equation can be plotted as-
From the above graph, it can be said that the graph for ln[A] v/s t for a first-order reaction is a straight line with slope -k.
The half-life of a chemical reaction refers to the time required by the reactant concentration to become half of its initial value. It is represented by .
Hence, according to the first order reaction, . Where [A] refers to the concentration of the reactant at any time ‘‘t’’ and [A]o represents the initial concentration of the reactant.
At half life, t = t1/2 , [A] =A0/2
Putting the value of [A] =A0/2 and t = t1/2 in the equation , we get
Taking ln on both sides, we get,
Hence half life of the first order reaction is 0.693/k, where k is the rate constant.
Below discussed are some of the questions asked in the NEET exam from first order reaction.
Question 1. A first order reaction has a specific reaction rate of 10-2 sec-1. How much time will it take for 20 g of the reactant to reduce to 5 g? [NEET 2017]
238.6 sec
138.6 sec
346.5 sec
693.0 sec
Ans. The rate of first order reaction is proportional to the first power of the concentration of the reaction.
Let us consider a reaction, R → P , wherein
R → P
At t=0 a 0
At t=t a-x x
After solving this equation, we get
Now, putting the values
t= 138.6 sec
Alternatively, this can be solved by the half life method. According to which after the first half life concentration becomes half and after the second half life, concentration becomes ¼ th of the initial concentration. Hence after two half life, the concentration becomes from 20g to 5g.
Now, 2t1/2= 69.3×2= 138.6 sec.
Hence option ‘’C’’ is correct.
Question 2. The correct difference between first and second-order reactions is that [NEET 2018]
a first-order reaction can be catalysed; a second-order reaction cannot be catalysed
the half-life of a first-order reaction does not depend on [A]o; the half-life of a second-order reaction does depend on [A]o
the rate of a first-order reaction does not depend on reactant concentrations; the rate of a second-order reaction does depend on reactant concentrations
the rate of a first-order reaction does depend on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations
Ans. For first Order reaction, rate is directly proportional to the first power of concentration.
For a reaction, A→B
Rate = -d[A]/dt = k[A] and half life is
Where unit of .
Hence
For second order reaction, For a reaction, A→B
Rate = and its half life is
Hence, The half-life of a first-order reaction does not depend on [A]o; the half-life of a second-order reaction does depend on [A]o
Option B is correct.
Question 3. If the rate constant for a first order reaction is k, the time (t) required for the completion of 99 per cent of the reaction is given by: [NEET 2019]
t = 0.693/k
t = 6.909/k
t = 4.606/k
t = 2.303/k
Ans. Let us consider a reaction, R → P , wherein
R → P
At t=0 a 0
At t=t a-x x
For the First Order reaction, Rate of reaction is proportional to the first power of the concentration of the reaction.
Unit of
and
Hence option C is correct.
Question 4. The rate constant for a first order reaction is The time required to reduce 2 g of the reactant to 0.2g is: [NEET 2020]
1000s
100s
200s
500s
Ans. Given,
Hence the given reaction is of first order.
Thus, we have:
Hence it is from the option of keeping th
Thus,
Therefore, Option(D) is correct.
Exam Date:12 May,2025 - 12 May,2025
Exam Date:25 May,2025 - 25 May,2025
Hello,
You can use our NEET College predictor tool to predict which college you can get based on your score :-
Hope it helps !
Hello,
If you are asking about SCB (State/Central Board) quota under AIIMS or IISER through NEET , then please note:
For SCB channel in IISER , NEET score is not accepted . IISER accepts applications through: IISER Aptitude Test (IAT), KVPY (until 2022), JEE Advanced, SCB channel (based on class 12 marks + IISER Aptitude Test).
If you are asking about NEET admission to MBBS/BDS in general and mean SCB as State Counselling Board , then:
For Government MBBS colleges , if you are from SC category , you usually need around 400 to 470+ marks in NEET (varies by state and college).
For Private colleges , cutoffs are lower, sometimes even around 250–350 marks for SC category.
Hope it helps !
Hi anamika
What kind of help you need like you want to know about syllabus or about how to prepare.
Please check this
Thanks
Hi anamika
As you didn't tell the year in which appear for neet so that I can guide you better I am assuming you are appearing for this year then you have to practice mock tests this time and revise the topics which yoh studied previous if you didn't study any topic then leave it or just get some important highlights from chapter and start practicing mix questions
Thanks.
Hello,
Yes, with 60% hearing loss, you may be eligible for the Persons with Disabilities (PwD) reservation in NEET PG 2025 .
As per the latest NMC (National Medical Commission) guidelines, candidates with a disability of 40% or more are eligible for the PwD quota. However, you need to get a valid disability certificate from an authorized medical board.
Hope it helps !
Orthotists and Prosthetists are professionals who provide aid to patients with disabilities. They fix them to artificial limbs (prosthetics) and help them to regain stability. There are times when people lose their limbs in an accident. In some other occasions, they are born without a limb or orthopaedic impairment. Orthotists and prosthetists play a crucial role in their lives with fixing them to assistive devices and provide mobility.
A career in pathology in India is filled with several responsibilities as it is a medical branch and affects human lives. The demand for pathologists has been increasing over the past few years as people are getting more aware of different diseases. Not only that, but an increase in population and lifestyle changes have also contributed to the increase in a pathologist’s demand. The pathology careers provide an extremely huge number of opportunities and if you want to be a part of the medical field you can consider being a pathologist. If you want to know more about a career in pathology in India then continue reading this article.
A veterinary doctor is a professional, working in animal healthcare. He or she conducts medical examinations, diagnoses, and treats various illnesses of animals. Animals have distinct internal organs and functions, requiring specialised attention from a veterinary doctor. A doctor who treats humans cannot offer the same level of care to animals due to these variations. Therefore, a veterinary doctor plays a critical role in animal welfare.
Veterinary professionals prevent illness by providing vaccines and offering advice on animal nutrition and overall health. Their knowledge extends beyond household animals and includes livestock, wildlife, and exotic animals. Individuals who love animals and want to treat their illnesses, injuries, and diseases must opt for a career as a veterinary doctor.
Speech therapists are essential medical professionals addressing speech disorders. Whether it's delayed speech in children or difficulties in pronunciation, these experts play a crucial role. This article explores how to become a speech therapist in India, covering courses, colleges, and the responsibilities of this impactful profession.
Gynaecology can be defined as the study of the female body. The job outlook for gynaecology is excellent since there is evergreen demand for one because of their responsibility of dealing with not only women’s health but also fertility and pregnancy issues. Although most women prefer to have a women obstetrician gynaecologist as their doctor, men also explore a career as a gynaecologist and there are ample amounts of male doctors in the field who are gynaecologists and aid women during delivery and childbirth.
The audiologist career involves audiology professionals who are responsible to treat hearing loss and proactively preventing the relevant damage. Individuals who opt for a career as an audiologist use various testing strategies with the aim to determine if someone has a normal sensitivity to sounds or not. After the identification of hearing loss, a hearing doctor is required to determine which sections of the hearing are affected, to what extent they are affected, and where the wound causing the hearing loss is found. As soon as the hearing loss is identified, the patients are provided with recommendations for interventions and rehabilitation such as hearing aids, cochlear implants, and appropriate medical referrals. While audiology is a branch of science that studies and researches hearing, balance, and related disorders.
An oncologist is a specialised doctor responsible for providing medical care to patients diagnosed with cancer. He or she uses several therapies to control the cancer and its effect on the human body such as chemotherapy, immunotherapy, radiation therapy and biopsy. An oncologist designs a treatment plan based on a pathology report after diagnosing the type of cancer and where it is spreading inside the body.
Are you searching for an ‘Anatomist job description’? An Anatomist is a research professional who applies the laws of biological science to determine the ability of bodies of various living organisms including animals and humans to regenerate the damaged or destroyed organs. If you want to know what does an anatomist do, then read the entire article, where we will answer all your questions.
A Narcotics Officer is an officer employed by the state to investigate the usage of drugs and their trafficking. A narcotics officer conducts undercover operations, investigates suspected drug dealers, executes raids and other appropriate actions for arresting these traffickers to reduce the circulation of drugs in the country.
A narcotics officer works in collaboration with other government agencies to stop drug trafficking at borders. He or she engages with various NGOs and public organisations to teach people about the dangerous effects of drug usage. A narcotics officer plays an important role in reducing the illegal activities of drug dealers and the circulation of drugs in the nation.
If we talk about a career as a research associate, it all comes down to one thing - curiosity towards nature and the passion to find answers. A career as a research associate is full of thrill and excitement. However, a research associate also faces a lot of challenges and failures while working on a project. A job of a research associate includes a spectrum of Science as a subject in detail.
A career as a Drug Inspector is regarded as one of the most diverse in the field of healthcare and pharmacy. Candidates must undergo a screening process administered by the UPSC and or SPSCs in order to become drug inspectors. Those who manage it through the selection process will have a rewarding career with a high salary.
A Biotechnologist is a professional who possesses strong knowledge and techniques that are utilised in creating and developing innovative products that improve the quality of human life standards. A biochemist uses biological organisms to create and improve goods and procedures for agriculture, medicine, and sustainability. He or she researches the genetic, chemical, and physical characteristics of cells, tissues, and organisms to determine how they can be used industrially.
A career as R&D Personnel requires researching, planning, and implementing new programs and protocols into their organization and overseeing new products’ development. He or she uses his or her creative abilities to improve the existing products as per the requirements of the target market.
Accorded Institution of Eminence by MoE, Govt. of India | NAAC A++ Grade | Ranked #4 India by NIRF 2024
Accorded Institution of Eminence by MoE, Govt. of India | NAAC A++ Grade | Ranked #4 India by NIRF 2024
Know possible Govt/Private MBBS/BDS Colleges based on your NEET rank
Register for Careers360 NEET Counseling & Admission Guidance Service.
Apply for Integrated M.Sc Biotechnology (5 Years, after 10+2) @ VIT Bhopal University | H-CTC 52 LPA
Accepted by more than 11,000 universities in over 150 countries worldwide