This pH calculator converts between the hydrogen ion concentration of a solution and its pH, and also returns the pOH and the hydroxide ion concentration, with a label telling you whether the solution is acidic, neutral or basic. The pH scale is the standard measure of acidity, running from below 0 for strong acids through 7 for neutral solutions like pure water up to 14 and beyond for strong bases. It is defined as the negative base-10 logarithm of the hydrogen ion concentration in moles per litre, which is why each whole step on the pH scale represents a tenfold change in acidity. You choose whether you are starting from a concentration or from a pH value, enter the number, and the calculator works out the rest. From a hydrogen ion concentration it takes the negative log to get the pH; from a pH it raises 10 to the negative pH to recover the concentration. It then uses the relationship that pH plus pOH equals 14 at 25 degrees Celsius to give the pOH and the matching hydroxide concentration. This is core chemistry for titrations, buffers, water testing, pool and aquarium care and biology. Enter a value to see the full set of results straight away.
From a concentration, the pH is the negative base-10 logarithm of the hydrogen ion concentration. From a pH, the concentration is 10 to the power of negative pH. The pOH is 14 minus the pH, and the hydroxide concentration is 10 to the power of negative pOH. A pH below 7 is acidic, exactly 7 is neutral, and above 7 is basic.
A hydrogen ion concentration of 0.001, which is 1 times 10 to the minus 3, moles per litre gives a pH of 3, an acidic solution. The pOH is 14 minus 3, which is 11.
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