GCSE Chemistry (AQA)

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H+ Concentration and pH

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Chemical changes Reactions of acids

H+ Concentration and pH

10:03 pH
Spec 4.4.2.6
Previous Ionic Equations Next Electrolysis of Solutions
  • Concentration measures the mass or amount of solute in a given volume of solvent or solution.
  • Solutions with the same volume can have different concentrations based on the number of solute particles.
  • Low concentration solutions have fewer solute particles spread out, while high concentration solutions have more particles packed together.
  • pH measures the concentration of hydrogen ions (H+) in a solution.
  • pH values are associated with color changes when using a universal indicator, ranging from red to green to purple as pH increases.
  • A neutral solution has equal numbers of H+ and OH- ions, with a pH of 7, like pure water.
  • Higher H+ concentration results in lower pH, making a solution more acidic.
  • Higher OH- concentration results in higher pH, making a solution more alkaline.
  • The pH scale is logarithmic; a decrease by one unit increases H+ concentration by a factor of 10.
  • Concentration is measured in moles per decimeter cubed (M).
  • Acids and alkalis can be described as concentrated or dilute based on the amount of dissolved solute.
  • Strong acids, like hydrochloric acid, are completely ionized in solution, while weak acids, like acetic acid, are only partially ionized.
  • Strong acids have lower pH values due to higher H+ concentration compared to weak acids at the same concentration.
  • Examples of strong acids include hydrochloric acid, nitric acid, and sulfuric acid.
  • Examples of weak acids include acetic acid, citric acid, and carbonic acid.
  • Strong acids are commonly found in laboratories and must be handled with care.
  • Weak acids are often found in everyday items like vinegar, lemons, and fizzy drinks.
  • The strength of an acid affects its pH; stronger acids have lower pH values.

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