Neutralisation reactions are everywhere in chemistry, from antacids in your...
Chemistry132 views·Updated 17 Jul 2026·2 pagesUnderstanding Chapter 21.3 – Acids and Neutralization Explained
1
of 2
Understanding Neutralisation and pH Curves
When you mix acids and bases, something fascinating happens - the pH doesn't change gradually throughout the reaction. Instead, there's a dramatic jump at one specific point called the equivalence point.
The equivalence point is where the volume of one solution exactly reacts with the volume of another. On a pH curve, you'll spot this as the centre of that steep, vertical section where pH rockets upward.
Looking at the graph, notice how the pH changes slowly at first (excess acid), then shoots up rapidly around 25 cm³ of added base, then levels off again (excess base). That vertical bit? That's your goldmine for accurate results.
Quick Tip: The steeper the vertical section, the more accurate your titration results will be!
2
of 2
Acid-Base Indicators and Endpoints
Here's the clever bit - you don't actually need expensive pH meters to find your equivalence point. Acid-base indicators do the job brilliantly by changing colour exactly when you need them to.
These indicators are weak acids (HA) that look completely different from their conjugate bases (A⁻). Think phenolphthalein (colourless to pink) or methyl orange (red to yellow). The magic happens because they change colour right in that vertical section of your pH curve.
The endpoint occurs when [HA] = [A⁻], meaning exactly half the indicator molecules have given up their protons. At this point, [H⁺] = Ka, so pH = pKa of the indicator.
Key Point: Choose your indicator so its pKa matches the pH of your equivalence point - that's how you get sharp, accurate colour changes!
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Chemistry132 views·Updated 17 Jul 2026·2 pagesUnderstanding Chapter 21.3 – Acids and Neutralization Explained
Neutralisation reactions are everywhere in chemistry, from antacids in your medicine cabinet to environmental chemistry. Understanding how to track these reactions using pH curves and indicators is essential for A-level chemistry and will help you master titration calculations.
1
of 2
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Understanding Neutralisation and pH Curves
When you mix acids and bases, something fascinating happens - the pH doesn't change gradually throughout the reaction. Instead, there's a dramatic jump at one specific point called the equivalence point.
The equivalence point is where the volume of one solution exactly reacts with the volume of another. On a pH curve, you'll spot this as the centre of that steep, vertical section where pH rockets upward.
Looking at the graph, notice how the pH changes slowly at first (excess acid), then shoots up rapidly around 25 cm³ of added base, then levels off again (excess base). That vertical bit? That's your goldmine for accurate results.
Quick Tip: The steeper the vertical section, the more accurate your titration results will be!
2
of 2Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Acid-Base Indicators and Endpoints
Here's the clever bit - you don't actually need expensive pH meters to find your equivalence point. Acid-base indicators do the job brilliantly by changing colour exactly when you need them to.
These indicators are weak acids (HA) that look completely different from their conjugate bases (A⁻). Think phenolphthalein (colourless to pink) or methyl orange (red to yellow). The magic happens because they change colour right in that vertical section of your pH curve.
The endpoint occurs when [HA] = [A⁻], meaning exactly half the indicator molecules have given up their protons. At this point, [H⁺] = Ka, so pH = pKa of the indicator.
Key Point: Choose your indicator so its pKa matches the pH of your equivalence point - that's how you get sharp, accurate colour changes!
We thought you’d never ask...
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.
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Students love us — and so will you.
4.6/5App Store
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Samantha KlichAndroid 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.
AnnaiOS user