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6 Dec 2025
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Identifying Anions and Cations: Key Tests
J
Jess Drew
@rj2105
Detecting Cations (Positive Ions)
Think of cations as the positive characters in chemistry - they're metal ions that have lost electrons. There are two main ways to spot them, and both involve watching for colour changes.
Flame tests are probably the most exciting way to identify cations. You simply heat your substance in a Bunsen burner's blue flame and watch the fireworks! Lithium gives a brilliant red flame, sodium burns bright yellow (like street lamps), and potassium creates a lovely lilac colour. Calcium produces an orange-red flame, whilst copper makes a distinctive green-blue colour.
The precipitate test is your backup method when flame tests aren't clear enough. Add some sodium hydroxide (NaOH) to your solution, and if cations are present, you'll get an insoluble solid with a telltale colour. Copper ions create a blue precipitate, iron(II) makes green, and iron(III) forms an orange-brown solid.
Top Tip: Remember that zinc gives a white precipitate, but it's sneaky - it dissolves if you add too much NaOH!
Detecting Anions (Negative Ions)
Anions are the negative ions that balance out those positive cations, and each type has its own detective test that's surprisingly straightforward.
For carbonate ions, just add some acid to your solution. If you see bubbles of CO₂ fizzing up, you've found your carbonate! It's like adding vinegar to baking soda - same reaction principle.
Sulphate ions need barium chloride to reveal themselves. Add this reagent and watch for a white precipitate to confirm sulphates are lurking in your solution.
Halide ions (chloride, bromide, and iodide) require a two-step dance. First add nitric acid, then silver nitrate, and the colour of the precipitate tells the whole story. Chloride gives white, bromide creates cream, and iodide produces yellow.
Real Lab Results: When scientists tested three mystery solutions, they found sodium carbonate , iron(III) sulphate , and copper chloride .
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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
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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
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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
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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
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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.
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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
Identifying Anions and Cations: Key Tests
J
Jess Drew
@rj2105
Ever wondered how chemists identify mystery substances in the lab? It's all about detecting anions (negative ions) and cations (positive ions) using clever chemical tests that produce distinctive colours and reactions.
Detecting Cations (Positive Ions)
Think of cations as the positive characters in chemistry - they're metal ions that have lost electrons. There are two main ways to spot them, and both involve watching for colour changes.
Flame tests are probably the most exciting way to identify cations. You simply heat your substance in a Bunsen burner's blue flame and watch the fireworks! Lithium gives a brilliant red flame, sodium burns bright yellow (like street lamps), and potassium creates a lovely lilac colour. Calcium produces an orange-red flame, whilst copper makes a distinctive green-blue colour.
The precipitate test is your backup method when flame tests aren't clear enough. Add some sodium hydroxide (NaOH) to your solution, and if cations are present, you'll get an insoluble solid with a telltale colour. Copper ions create a blue precipitate, iron(II) makes green, and iron(III) forms an orange-brown solid.
Top Tip: Remember that zinc gives a white precipitate, but it's sneaky - it dissolves if you add too much NaOH!
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Detecting Anions (Negative Ions)
Anions are the negative ions that balance out those positive cations, and each type has its own detective test that's surprisingly straightforward.
For carbonate ions, just add some acid to your solution. If you see bubbles of CO₂ fizzing up, you've found your carbonate! It's like adding vinegar to baking soda - same reaction principle.
Sulphate ions need barium chloride to reveal themselves. Add this reagent and watch for a white precipitate to confirm sulphates are lurking in your solution.
Halide ions (chloride, bromide, and iodide) require a two-step dance. First add nitric acid, then silver nitrate, and the colour of the precipitate tells the whole story. Chloride gives white, bromide creates cream, and iodide produces yellow.
Real Lab Results: When scientists tested three mystery solutions, they found sodium carbonate , iron(III) sulphate , and copper chloride .
We thought you’d never ask...
What is the Knowunity AI companion?
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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
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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