Subjects

Careers

Open the App

Subjects

Easy Kc Chemistry: Calculate Equilibrium Constants!

Open

23

1

user profile picture

Aysha Akmal

24/01/2023

Chemistry

Edexcel A Level Chemistry - Topic 11 Further Equilibrium

Subjects

/

Chemistry

/

Physical chemistry

/

Chemical equilibria, le chateliers principle and kc

Easy Kc Chemistry: Calculate Equilibrium Constants!

A comprehensive guide to equilibrium constant calculations and related concepts in chemistry, focusing on Kc and Kp calculations, heterogeneous equilibria, and the effects of changing conditions.

  • Equilibrium law fundamentals cover both homogeneous and heterogeneous reactions
  • How to calculate Kc in chemistry involves understanding concentration-based equilibrium expressions
  • Kp calculations specifically deal with gaseous equilibria using partial pressures
  • Effects of temperature on equilibrium constants are crucial for understanding system behavior
  • Practical applications include ICE tables and experimental determination methods
  • Changes in concentration and pressure affect equilibrium position but not the constant value at constant temperature
...

24/01/2023

519

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

View

Calculating Kc and Heterogeneous Equilibria

This section delves deeper into the process of calculating Kc and introduces the concept of heterogeneous equilibria.

To calculate Kc:

  1. Write the balanced equation
  2. Determine initial amounts of reactants and products
  3. Identify given equilibrium amounts
  4. Calculate other equilibrium amounts using stoichiometry
  5. Substitute values into the Kc expression

Example: For the reaction 2NOClgg ⇌ 2NOgg + Cl₂gg Given: 1.00 mol NOCl in 0.50 dm³ flask, 0.33 mol NO at equilibrium Kc = NONO² Cl2Cl₂ / NOClNOCl² = 0.0800 mol dm⁻³

Heterogeneous equilibria involve substances in different phases. In these systems, solids and pure liquids are not included in the Kc expression as their concentrations remain effectively constant.

Highlight: For heterogeneous equilibria, only include gases and aqueous species in the Kc expression.

Example: For CaCO₃ss ⇌ CaOss + CO₂gg, Kc = CO2CO₂

This simplification is due to the constant density of solids and pure liquids, which makes their concentrations invariant in the equilibrium expression.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

View

Gaseous Equilibria and Kp

This section introduces the concept of Kp, which is used for gaseous equilibria where partial pressures are more easily measured than concentrations.

Kp is expressed using partial pressures of gases instead of concentrations:

For aAgg + bBgg ⇌ cCgg + dDgg, Kp = PCc×PDdP_C^c × P_D^d / PAa×PBbP_A^a × P_B^b

Where P_A, P_B, P_C, and P_D are the partial pressures of gases A, B, C, and D respectively.

Vocabulary: Mole fraction - The proportion of a particular gas in a mixture, calculated as molesofgasmoles of gas / totalmolesofallgasestotal moles of all gases.

Vocabulary: Partial pressure - The pressure exerted by a single gas in a mixture, calculated as molefractionmole fraction × totalpressuretotal pressure.

To calculate Kp:

  1. Determine mole fractions of gases
  2. Calculate partial pressures
  3. Substitute values into the Kp expression

Example: For N₂gg + 3H₂gg ⇌ 2NH₃gg Given: 2.15 mol N₂, 6.75 mol H₂, 1.41 mol NH₃, total pressure 10.0 atm Calculate mole fractions, then partial pressures, and finally Kp

Understanding Kp is crucial for analyzing gaseous equilibria and complements the use of Kc for solution-based systems.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

View

Effects of Temperature on Equilibrium Constants

This section would typically discuss how temperature changes affect equilibrium constants and the position of equilibrium. However, the provided transcript does not contain specific information on this topic.

Highlight: The effects of temperature on equilibrium constants are an important aspect of chemical equilibria, but are not covered in the given material.

In general, temperature changes can shift the equilibrium position and alter the value of the equilibrium constant. This relationship is described by Le Chatelier's Principle and the van 't Hoff equation.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

View

Practice Problems and Applications

This section would usually provide additional practice problems and real-world applications of equilibrium constant calculations. However, the given transcript does not include such content.

Applying equilibrium concepts to practical situations helps reinforce understanding and demonstrates the relevance of these calculations in various fields of chemistry and chemical engineering.

Highlight: Practice problems are essential for mastering equilibrium constant calculations and understanding how to apply these concepts in different scenarios.

Students are encouraged to seek additional resources for practice problems related to Kc and Kp calculations, as well as explore how these concepts are used in industrial processes and environmental chemistry.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

View

Page 5: Effects of Changing Conditions

This page examines how various factors affect equilibrium constants and positions.

Definition: Le Chatelier's Principle explains how systems respond to changes in conditions.

Example: 2CrO₄²⁻aqaq + 2H⁺aqaq ⇌ Cr₂O₇²⁻aqaq + H₂Oll demonstrates how concentration changes affect equilibrium.

Highlight: Changing concentration does not alter Kc value as long as temperature remains constant.

Similar content

Know Equilibrium notess thumbnail

7

218

S5

Equilibrium notess

Can't find what you're looking for? Explore other subjects.

Knowunity is the #1 education app in five European countries

Knowunity has been named a featured story on Apple and has regularly topped the app store charts in the education category in Germany, Italy, Poland, Switzerland, and the United Kingdom. Join Knowunity today and help millions of students around the world.

Ranked #1 Education App

Download in

Google Play

Download in

App Store

Knowunity is the #1 education app in five European countries

4.9+

Average app rating

21 M

Pupils love Knowunity

#1

In education app charts in 17 countries

950 K+

Students have uploaded notes

Still not convinced? See what other students are saying...

iOS User

I love this app so much, I also use it daily. I recommend Knowunity to everyone!!! I went from a D to an A with it :D

Philip, iOS User

The app is very simple and well designed. So far I have always found everything I was looking for :D

Lena, iOS user

I love this app ❤️ I actually use it every time I study.

Subjects

Chemistry

Physical chemistry

Chemical equilibria, le chateliers principle and kc

 

Chemistry

•

519

•

21 Jul 2025

•

6 pages

Easy Kc Chemistry: Calculate Equilibrium Constants!

user profile picture

Aysha Akmal

@ayshakmal

A comprehensive guide to equilibrium constant calculations and related concepts in chemistry, focusing on Kc and Kp calculations, heterogeneous equilibria, and the effects of changing conditions.

  • Equilibrium law fundamentals cover both homogeneous and heterogeneous reactions
  • How to calculate Kc in... Show more

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Calculating Kc and Heterogeneous Equilibria

This section delves deeper into the process of calculating Kc and introduces the concept of heterogeneous equilibria.

To calculate Kc:

  1. Write the balanced equation
  2. Determine initial amounts of reactants and products
  3. Identify given equilibrium amounts
  4. Calculate other equilibrium amounts using stoichiometry
  5. Substitute values into the Kc expression

Example: For the reaction 2NOClgg ⇌ 2NOgg + Cl₂gg Given: 1.00 mol NOCl in 0.50 dm³ flask, 0.33 mol NO at equilibrium Kc = NONO² Cl2Cl₂ / NOClNOCl² = 0.0800 mol dm⁻³

Heterogeneous equilibria involve substances in different phases. In these systems, solids and pure liquids are not included in the Kc expression as their concentrations remain effectively constant.

Highlight: For heterogeneous equilibria, only include gases and aqueous species in the Kc expression.

Example: For CaCO₃ss ⇌ CaOss + CO₂gg, Kc = CO2CO₂

This simplification is due to the constant density of solids and pure liquids, which makes their concentrations invariant in the equilibrium expression.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Gaseous Equilibria and Kp

This section introduces the concept of Kp, which is used for gaseous equilibria where partial pressures are more easily measured than concentrations.

Kp is expressed using partial pressures of gases instead of concentrations:

For aAgg + bBgg ⇌ cCgg + dDgg, Kp = PCc×PDdP_C^c × P_D^d / PAa×PBbP_A^a × P_B^b

Where P_A, P_B, P_C, and P_D are the partial pressures of gases A, B, C, and D respectively.

Vocabulary: Mole fraction - The proportion of a particular gas in a mixture, calculated as molesofgasmoles of gas / totalmolesofallgasestotal moles of all gases.

Vocabulary: Partial pressure - The pressure exerted by a single gas in a mixture, calculated as molefractionmole fraction × totalpressuretotal pressure.

To calculate Kp:

  1. Determine mole fractions of gases
  2. Calculate partial pressures
  3. Substitute values into the Kp expression

Example: For N₂gg + 3H₂gg ⇌ 2NH₃gg Given: 2.15 mol N₂, 6.75 mol H₂, 1.41 mol NH₃, total pressure 10.0 atm Calculate mole fractions, then partial pressures, and finally Kp

Understanding Kp is crucial for analyzing gaseous equilibria and complements the use of Kc for solution-based systems.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

Effects of Temperature on Equilibrium Constants

This section would typically discuss how temperature changes affect equilibrium constants and the position of equilibrium. However, the provided transcript does not contain specific information on this topic.

Highlight: The effects of temperature on equilibrium constants are an important aspect of chemical equilibria, but are not covered in the given material.

In general, temperature changes can shift the equilibrium position and alter the value of the equilibrium constant. This relationship is described by Le Chatelier's Principle and the van 't Hoff equation.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Practice Problems and Applications

This section would usually provide additional practice problems and real-world applications of equilibrium constant calculations. However, the given transcript does not include such content.

Applying equilibrium concepts to practical situations helps reinforce understanding and demonstrates the relevance of these calculations in various fields of chemistry and chemical engineering.

Highlight: Practice problems are essential for mastering equilibrium constant calculations and understanding how to apply these concepts in different scenarios.

Students are encouraged to seek additional resources for practice problems related to Kc and Kp calculations, as well as explore how these concepts are used in industrial processes and environmental chemistry.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

Page 5: Effects of Changing Conditions

This page examines how various factors affect equilibrium constants and positions.

Definition: Le Chatelier's Principle explains how systems respond to changes in conditions.

Example: 2CrO₄²⁻aqaq + 2H⁺aqaq ⇌ Cr₂O₇²⁻aqaq + H₂Oll demonstrates how concentration changes affect equilibrium.

Highlight: Changing concentration does not alter Kc value as long as temperature remains constant.

equilibrium law states that, aA + bB cC + dD EQUILIBRIUIM RECAP *NOTE System must be at constant temperature homogeneous reactions equilibri

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Equilibrium Law and Constant (Kc)

The equilibrium law is a fundamental concept in chemistry that describes the state of a reversible reaction when the forward and reverse rates are equal. This section introduces the equilibrium constant Kc and its calculation.

For a general reaction aA + bB ⇌ cC + dD, the equilibrium constant Kc is expressed as:

Kc = CC^c DD^d / AA^a BB^b

Where AA, BB, CC, and DD represent the equilibrium concentrations of reactants and products.

Highlight: The equilibrium constant Kc is only valid for systems at constant temperature.

Example: For the reaction CH₃CO₂H aqaq + C₂H₅OH aqaq ⇌ CH₃CO₂C₂H₅ aqaq + H₂O ll, Kc = CH3CO2C2H5(aq)CH₃CO₂C₂H₅ (aq) H2O(l)H₂O (l) / CH3CO2H(aq)CH₃CO₂H (aq) C2H5OH(aq)C₂H₅OH (aq)

The units of Kc depend on the stoichiometry of the reaction. In some cases, Kc may be unitless.

Vocabulary: ICE table - A method for organizing Initial, Change, and Equilibrium concentrations in equilibrium calculations.

The value of Kc provides information about the position of equilibrium:

  • Large Kc: Products predominate at equilibrium
  • Kc ≈ 1: Significant amounts of both reactants and products present
  • Small Kc: Reactants predominate at equilibrium

Definition: Equilibrium position - The relative amounts of reactants and products present when a system reaches equilibrium.

We thought you’d never ask...

What is the Knowunity AI companion?

Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.

Where can I download the Knowunity app?

You can download the app from Google Play Store and Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.9/5

App Store

4.8/5

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

Best app on earth! no words because it’s too good

Thomas R

iOS user

Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.

Basil

Android user

This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.

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

very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.

Rohan U

Android user

I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.

Xander S

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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now

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

Best app on earth! no words because it’s too good

Thomas R

iOS user

Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.

Basil

Android user

This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.

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

very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.

Rohan U

Android user

I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.

Xander S

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 apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now

Paul T

iOS user