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GCSE Chemistry · key term
The amount of hydrogen ions present per unit volume of solution.
Used by Edexcel and OCR
Specification 3.5 · Paper 1
The amount of hydrogen ions, , present in a given volume of solution.
Revise: pH and Logarithmic ConcentrationThe pH scale is logarithmic, so a change of one pH unit represents a tenfold change in hydrogen ion concentration.
Specification C3.3j · Paper 1 (Foundation), Paper 3 (Higher)
Revise: Logarithmic pH ScaleThe pH value tells us about the concentration of these ions: a solution with a greater hydrogen ion concentration has a lower pH.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
The amount of hydrogen ions, , present per unit volume of a solution.
Revise: pH and hydrogen ion concentrationA greater hydrogen ion concentration corresponds to a lower pH.
Read the direction carefully: multiplying hydrogen ion concentration by 10 lowers pH by 1; it does not lower it by 10.
When comparing solutions, state both the size and direction of the difference: for example, “100 times the hydrogen ion concentration”, rather than simply “100 times more acidic”.
Always state the direction of change: a lower pH means a higher hydrogen ion concentration; a higher pH means a lower hydrogen ion concentration.
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