Acids, Bases and the pH Scale: A GCSE Chemistry Essentials Guide

Understanding Acids and Bases Acids and bases are two fundamental classes of compounds that play a crucial role in many chemical reactions. An acid is a substan...

Understanding Acids and Bases

Acids and bases are two fundamental classes of compounds that play a crucial role in many chemical reactions. An acid is a substance that releases hydrogen ions (H+) when dissolved in water, while a base is a substance that releases hydroxide ions (OH-) when dissolved in water.

The pH Scale

The pH scale is a logarithmic scale used to measure the acidity or basicity of a solution. It ranges from 0 to 14, with 7 being neutral. Solutions with a pH less than 7 are considered acidic, while those with a pH greater than 7 are considered basic (alkaline).

Worked Example: Calculating pH

Problem: Calculate the pH of a solution with a hydrogen ion concentration of 1 x 10-5 mol/L.

Solution:

  1. The pH is related to the hydrogen ion concentration [H+] by the equation: pH = -log[H+]
  2. Substituting the given value: pH = -log(1 x 10-5) = 5

Therefore, the pH of the solution is 5, which is acidic.

Neutralisation Reactions

When an acid and a base are mixed, they undergo a neutralisation reaction, where the hydrogen ions from the acid react with the hydroxide ions from the base to form water. The products of this reaction are a salt and water.

Preparing Salts

Salts can be prepared by various methods, including:

Electrolysis

Electrolysis is the process of using an electric current to drive a non-spontaneous redox reaction. It can be used to extract metals from molten or aqueous ionic compounds. Half-equations are used to represent the oxidation and reduction processes occurring during electrolysis.

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📚 Category: GCSE Chemistry