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AP Chemistry
Nov 24, 2025
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Rate laws are the mathematical expressions that show how reaction rates depend on reactant concentrations. Understanding rate laws... Show more
![Rate Laws:
Differential Rate Law express/reveal the relationship
between the concentration of reactants & the rate of
reaction
↳ Rate= K[A]](/_next/image?url=https%3A%2F%2Fcontent-eu-central-1.knowunity.com%2FCONTENT%2FMooQhHOKoQxfxpajUQrs_image_page_1.webp&w=2048&q=75)
Rate laws tell us exactly how reactant concentrations influence reaction rates. The general form is Rate = k^x^y, where k is the rate constant, and are reactant concentrations, and x and y are the "orders" of the reaction.
The order of a reaction shows the mathematical relationship between concentration and rate. For first-order reactions, if you double the concentration, the rate doubles. In second-order reactions, doubling concentration quadruples the rate. And for third-order reactions, doubling concentration makes the rate eight times faster!
Some reactions have special orders too. Zero-order reactions don't change rate when concentration changes. Negative-order reactions actually slow down as concentration increases.
💡 Remember Reaction orders CANNOT be determined just by looking at a balanced chemical equation. You need actual experimental data to figure them out!
![Rate Laws:
Differential Rate Law express/reveal the relationship
between the concentration of reactants & the rate of
reaction
↳ Rate= K[A]](/_next/image?url=https%3A%2F%2Fcontent-eu-central-1.knowunity.com%2FCONTENT%2FMooQhHOKoQxfxpajUQrs_image_page_2.webp&w=2048&q=75)
When given experimental data, you can figure out the order of reaction for each reactant by comparing trials where one concentration changes while others remain constant. Let's look at the reaction 2NO(g) + Cl₂(g) → 2NOCl(g).
In trials where stays constant but doubles, the rate increases four times. This means the reaction is second order with respect to NO. When stays constant but doubles, the rate doubles, showing it's first order with respect to Cl₂.
The overall reaction order is the sum of individual orders, making this a third-order reaction (2 + 1 = 3). Once you know the orders, you can calculate the rate constant (k) by plugging values into the rate equation.
🔬 Pro tip When analyzing experimental data, always look for trials where only one variable changes—this is the easiest way to determine each reactant's order!
![Rate Laws:
Differential Rate Law express/reveal the relationship
between the concentration of reactants & the rate of
reaction
↳ Rate= K[A]](/_next/image?url=https%3A%2F%2Fcontent-eu-central-1.knowunity.com%2FCONTENT%2FMooQhHOKoQxfxpajUQrs_image_page_3.webp&w=2048&q=75)
There are multiple ways to determine a rate law from experimental data. The comparison method looks at how rates change when concentrations change. For example, if doubling makes the rate four times faster, NO must be second order.
For more complex situations, you can use a mathematical approach. Set up equations using different trials and divide them to eliminate variables. This helps isolate the order for each reactant one at a time.
Once you've determined all orders, you can write the complete rate law. For our example reaction , the rate law is Rate = k². For another reaction , careful analysis shows the rate law is Rate = k².
🧮 Math shortcut When concentrations double and you want to find the order, use this relationship if rate increases by factor of 2ⁿ, then the order is n!
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Learn about synthesis, combustion, decomposition, and replacement reactions in chemistry.
ChemistryAn introduction to chemistry including the different branches of chemistry.
ChemistryLearn about the reactivity and properties of metals, alkali metals, alkaline earth metals, and transition metals in the periodic table.
ChemistryLearn about Henry Moseley's contribution to the modern periodic table and the arrangement of elements based on atomic number and properties.
Chemistrypercentage composition of a compound
ChemistryThis note contains the summary of the topics redox reaction, electrochemistry, nuclear chemistry, and stoichiometry.
AP ChemistryApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Rate laws are the mathematical expressions that show how reaction rates depend on reactant concentrations. Understanding rate laws helps you predict how changes in concentration affect the speed of chemical reactions—essential knowledge for both chemistry class and real-world applications.
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Rate laws tell us exactly how reactant concentrations influence reaction rates. The general form is Rate = k^x^y, where k is the rate constant, and are reactant concentrations, and x and y are the "orders" of the reaction.
The order of a reaction shows the mathematical relationship between concentration and rate. For first-order reactions, if you double the concentration, the rate doubles. In second-order reactions, doubling concentration quadruples the rate. And for third-order reactions, doubling concentration makes the rate eight times faster!
Some reactions have special orders too. Zero-order reactions don't change rate when concentration changes. Negative-order reactions actually slow down as concentration increases.
💡 Remember: Reaction orders CANNOT be determined just by looking at a balanced chemical equation. You need actual experimental data to figure them out!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
When given experimental data, you can figure out the order of reaction for each reactant by comparing trials where one concentration changes while others remain constant. Let's look at the reaction 2NO(g) + Cl₂(g) → 2NOCl(g).
In trials where stays constant but doubles, the rate increases four times. This means the reaction is second order with respect to NO. When stays constant but doubles, the rate doubles, showing it's first order with respect to Cl₂.
The overall reaction order is the sum of individual orders, making this a third-order reaction (2 + 1 = 3). Once you know the orders, you can calculate the rate constant (k) by plugging values into the rate equation.
🔬 Pro tip: When analyzing experimental data, always look for trials where only one variable changes—this is the easiest way to determine each reactant's order!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
There are multiple ways to determine a rate law from experimental data. The comparison method looks at how rates change when concentrations change. For example, if doubling makes the rate four times faster, NO must be second order.
For more complex situations, you can use a mathematical approach. Set up equations using different trials and divide them to eliminate variables. This helps isolate the order for each reactant one at a time.
Once you've determined all orders, you can write the complete rate law. For our example reaction , the rate law is Rate = k². For another reaction , careful analysis shows the rate law is Rate = k².
🧮 Math shortcut: When concentrations double and you want to find the order, use this relationship: if rate increases by factor of 2ⁿ, then the order is n!
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Learn about synthesis, combustion, decomposition, and replacement reactions in chemistry.
ChemistryAn introduction to chemistry including the different branches of chemistry.
ChemistryLearn about the reactivity and properties of metals, alkali metals, alkaline earth metals, and transition metals in the periodic table.
ChemistryLearn about Henry Moseley's contribution to the modern periodic table and the arrangement of elements based on atomic number and properties.
Chemistrypercentage composition of a compound
ChemistryThis note contains the summary of the topics redox reaction, electrochemistry, nuclear chemistry, and stoichiometry.
AP ChemistryApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
