The pH Scale and Neutralisation

• Understand that acids produce active hydrogen ions when placed into aqueous solutions.
• Understand that aqueous solutions of alkalis predictably contain hydroxide ions.
• Describe the pH scale (ranging from 0 to 14) as a definitive measure of the acidity or alkalinity of a given solution.
• Understand that pH can be accurately measured using distinct tools such as universal indicator or an electronic pH probe.
• Classify a solution with pH 7 as neutral, aqueous solutions below pH 7 as acidic, and aqueous solutions above pH 7 as alkaline.
• Explain that in an active neutralization reaction, hydrogen ions from the acid react with hydroxide ions from the alkali to synthesize water.
• Represent typical neutralization reactions through a balanced ionic equation.

$H^{+}(aq) + OH^{-}(aq) \rightarrow H_2O(l)$

• Describe the application of a universal or wide-range indicator to ascertain the approximate pH level of an unknown solution.
• Use the comprehensive pH scale to confidently identify whether a solution is considered acidic or alkaline.