Chemical Changes


Acids and Alkalis

Acids- Substances producing more hydrogen ions than hydroxide ions when dissolved in water. Acids form acidic solutions in water. Acidic solutions have pH values less than 7. Acids produce hydrogen ions, H⁺ in aqueous solution. For example:

HCl(aq) → H+(aq) + Cl-(aq) 

Alkalis- Substances producing more hydroxide ions than hydrogen ions when dissolved in water. Alkalis form alkaline solutions in water. Alkaline solutions have pH values greater than 7.Alkalis produce hydroxide ions, OH- in aqueous solution. For example:

NaOH(aq) → Na+(aq) + OH-(aq) 

pH Scale- The pH scale measures the acidity or alkalinity of a solution. The pH of a solution can be measured using a pH probe, or estimated using universal indicator and a colour chart.


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