Chemistry - 4CH1 PearsonEdexcel

Acids, Alkalis And Titrations

Overview

From the sting of a wasp to the fizz of a dissolving antacid tablet, acids and alkalis are at work everywhere. Understanding what makes a substance acidic or alkaline, and knowing how to measure and neutralise that character, is one of the most practical skills chemistry offers.

In this lesson you will learn how indicators reveal pH, why acids produce hydrogen ions while alkalis produce hydroxide ions, and how a titration lets you find the exact volume of one solution needed to neutralise another. These ideas run through Edexcel Paper 1 and Paper 2 every session.

Objectives

  1. describe the use of litmus, phenolphthalein and methyl orange to distinguish between acidic and alkaline solutions
  2. understand how to use the pH scale, from 0-14, can be used to classify solutions as strongly acidic (0-3), weakly acidic (4-6), neutral (7), weakly alkaline (8-10) and strongly alkaline (11-14)
  3. describe the use of universal indicator to measure the approximate pH value of an aqueous solution
  4. know that acids in aqueous solution are a source of hydrogen ions and alkalis in a aqueous solution are a source of hydroxide ions
  5. know that alkalis can neutralise acids
  6. describe how to carry out an acid-alkali titration

Lesson Note

You cannot see whether a solution is acidic or alkaline just by looking at it. Hydrochloric acid and water can both appear as colourless liquids, yet one will corrode metal while the other is safe to drink. Chemists solved this problem centuries ago with indicators, coloured dyes that change hue in response to acidity. Today, the pH scale gives us a single number that captures how acidic or alkaline a solution is, and titrations let us measure concentrations with precision.

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Lesson Evaluation

Congratulations on completing the lesson on Acids, Alkalis And Titrations. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

  1. Which indicator turns pink in alkaline solution and is colourless in acid? A) Litmus B) Methyl orange C) Phenolphthalein D) Universal indicator Answer: C
  2. A solution has a pH of 2. It is best described as: A) Weakly acidic B) Strongly acidic C) Neutral D) Weakly alkaline Answer: B
  3. Which ion is responsible for making a solution acidic? A) OH- B) Na+ C) H+ D) Cl- Answer: C
  4. What is produced when an acid reacts with an alkali? A) Salt and hydrogen B) Salt and water C) Salt, water and carbon dioxide D) Salt and oxygen Answer: B
  5. In a titration, concordant results are readings that agree within: A) 1.0 cm3 B) 0.5 cm3 C) 0.1 cm3 D) 0.01 cm3 Answer: C

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Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.

Full lesson notes with diagrams
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Available on the Green Bridge App

Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.

Full lesson notes with diagrams
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Study offline, anytime, anywhere
Available on Android, Windows, macOS, and Linux

Practice Mock Questions

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