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pH - a more scientific definition
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| pH - a more scientific definitionpH refers to the relative concentration of H+ ions in solution. The numerical value of the pH is the negative of the exponent of the molar concentration. Thus low pH values indicate high concentrations of H+ ions (acid), and high pH values indicate low concentrations. Ionisation - the process of spontaneous ion formation H2O > OH- + H+ In 1 litre of water about 1 water molecule out of each 550 million is ionised at any instant in time corresponding to 1/10,000,000 of a mole of H+ ions ( a mole is defined as the weight in grams that corresponds to to the summed atomic weights of all the atoms of a molecule - its molecular mass. In the case of H+ the molecular mass equals 1, and a mole of H+ ions would weigh 1 gram.) The molar concentration of hydrogen ions in pure water, 1/10,000,000 can be written more easily by employing exponential notation. - count the number of decimal places after the digit "1" in the denominator [H+] = 1/10,000,000 Brackets are used to indicate the chemical concentration of H+ . since there are 7 decimal places the molar concentration is 10 -7 moles per litre. Any substance that dissociates to form H+ ions when dissolved in water is called an acid. The exponents in the exponential notation of H+ ion concentration are used as a convenient indication of acid strength called the pH scale. pH is normally expressed as a positive number and is the negative of the exponent of the molar concentration. Pure water has a molar H+ concentration of 10 -7 and so a pH value of 7. The stronger the acid the more H+ ions it produces and so the lower its pH.
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