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50
•
22 Dec 2025
•
Rebekah
@rebekah_liz
Titrations are essential analytical techniques in chemistry that help you... Show more
Working out unknown concentrations becomes straightforward once you've got the formula down. You'll use C = n/V where C is concentration (mol dm⁻³), n is moles, and V is volume (dm³).
The key is recognising that in a 1:1 reaction ratio, both solutions contain the same number of moles. Convert your volumes from cm³ to dm³ by dividing by 1000, then calculate moles of the known solution using n = CV.
Since the moles are equal, you can find the unknown concentration by rearranging C = n/V. In this example, 0.01 moles in 0.025 dm³ gives 0.4 mol dm⁻³.
Quick Tip: Always check your reaction equation to confirm the mole ratio - it's not always 1:1!
Double titrations tackle mixtures containing two different compounds that react at different stages. You'll use two indicators to spot each endpoint clearly.
In the first stage with phenolphthalein, HCl neutralises all the NaOH plus half the Na₂CO₃ (22 cm³ used). The second stage with methyl orange completes the Na₂CO₃ reaction (8.25 cm³ more acid).
The clever bit is working backwards: the second titration tells you the total Na₂CO₃ present, whilst the first titration reveals the combined effect. Subtract to find the pure NaOH amount.
Calculate each concentration using C = (n × 1000)/V, giving you 0.055 mol dm⁻³ for NaOH and 0.033 mol dm⁻³ for Na₂CO₃.
Remember: Phenolphthalein changes first, then methyl orange - this sequence is crucial for double titrations!
The final step in double titrations involves converting your mole calculations into proper concentration values. You'll need the formula C = (n × 1000)/V where n is moles and V is volume in cm³.
For the NaOH calculation, take your moles (1.375 × 10⁻³) and multiply by 1000, then divide by the original sample volume (25 cm³). This gives you 0.055 mol dm⁻³.
The Na₂CO₃ follows the same pattern: 8.25 × 10⁻⁴ moles converted gives 0.033 mol dm⁻³. These final answers tell you exactly what's in your original mixture.
Top Tip: Double-check your arithmetic here - small calculation errors can throw off your entire analysis!
Back titrations are your go-to method when direct titration isn't practical, especially with insoluble samples or slow reactions. You add excess acid, then titrate backwards to find what wasn't used.
Start by calculating the excess HCl that didn't react with your sample. The NaOH titration (10.9 cm³) tells you exactly how much acid was left over - that's 2.485 × 10⁻³ moles.
Subtract this excess from your initial HCl amount (0.02 moles) to find what actually reacted with the Ba(OH)₂. Remember the 2:1 ratio in the equation - each Ba(OH)₂ needs two HCl molecules.
Finally, convert moles to mass using molar mass, then calculate percentage purity: × 100. Here, you get 90.8% purity.
Key Point: Back titrations are perfect when your sample doesn't dissolve well or reacts too slowly for direct methods!
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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
Rebekah
@rebekah_liz
Titrations are essential analytical techniques in chemistry that help you determine unknown concentrations by carefully measuring how much of one solution reacts with another. You'll master three key types: basic titrations, double titrations for mixtures, and back titrations for tricky... Show more
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Working out unknown concentrations becomes straightforward once you've got the formula down. You'll use C = n/V where C is concentration (mol dm⁻³), n is moles, and V is volume (dm³).
The key is recognising that in a 1:1 reaction ratio, both solutions contain the same number of moles. Convert your volumes from cm³ to dm³ by dividing by 1000, then calculate moles of the known solution using n = CV.
Since the moles are equal, you can find the unknown concentration by rearranging C = n/V. In this example, 0.01 moles in 0.025 dm³ gives 0.4 mol dm⁻³.
Quick Tip: Always check your reaction equation to confirm the mole ratio - it's not always 1:1!
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Double titrations tackle mixtures containing two different compounds that react at different stages. You'll use two indicators to spot each endpoint clearly.
In the first stage with phenolphthalein, HCl neutralises all the NaOH plus half the Na₂CO₃ (22 cm³ used). The second stage with methyl orange completes the Na₂CO₃ reaction (8.25 cm³ more acid).
The clever bit is working backwards: the second titration tells you the total Na₂CO₃ present, whilst the first titration reveals the combined effect. Subtract to find the pure NaOH amount.
Calculate each concentration using C = (n × 1000)/V, giving you 0.055 mol dm⁻³ for NaOH and 0.033 mol dm⁻³ for Na₂CO₃.
Remember: Phenolphthalein changes first, then methyl orange - this sequence is crucial for double titrations!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The final step in double titrations involves converting your mole calculations into proper concentration values. You'll need the formula C = (n × 1000)/V where n is moles and V is volume in cm³.
For the NaOH calculation, take your moles (1.375 × 10⁻³) and multiply by 1000, then divide by the original sample volume (25 cm³). This gives you 0.055 mol dm⁻³.
The Na₂CO₃ follows the same pattern: 8.25 × 10⁻⁴ moles converted gives 0.033 mol dm⁻³. These final answers tell you exactly what's in your original mixture.
Top Tip: Double-check your arithmetic here - small calculation errors can throw off your entire analysis!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Back titrations are your go-to method when direct titration isn't practical, especially with insoluble samples or slow reactions. You add excess acid, then titrate backwards to find what wasn't used.
Start by calculating the excess HCl that didn't react with your sample. The NaOH titration (10.9 cm³) tells you exactly how much acid was left over - that's 2.485 × 10⁻³ moles.
Subtract this excess from your initial HCl amount (0.02 moles) to find what actually reacted with the Ba(OH)₂. Remember the 2:1 ratio in the equation - each Ba(OH)₂ needs two HCl molecules.
Finally, convert moles to mass using molar mass, then calculate percentage purity: × 100. Here, you get 90.8% purity.
Key Point: Back titrations are perfect when your sample doesn't dissolve well or reacts too slowly for direct methods!
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.
You can download the app from Google Play Store and 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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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
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