document.write( "Question 331174: what does pH mean?
\n" ); document.write( " \n" ); document.write( "
Algebra.Com's Answer #237403 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
 \r\n" );
document.write( " \r\n" );
document.write( "pH is -1 times the logarithm (base 10) of the hydrogen ion concentration\r\n" );
document.write( "of a compound.  It was originally defined by Danish biochemist \r\n" );
document.write( "Soren Peter Lauritz Sørensen in 1909.\r\n" );
document.write( "\r\n" );
document.write( "In chemistry you often see:\r\n" );
document.write( "\r\n" );
document.write( "pH = -log[H+] \r\n" );
document.write( "\r\n" );
document.write( "where log is a base-10 logarithm and [H+] is the concentration of hydrogen \r\n" );
document.write( "ions in moles per liter of solution. According to the Compact Oxford English\r\n" );
document.write( "Dictionary, the \"p\" stands for the German word for \"power\", \"potenz\", so pH is\r\n" );
document.write( "an abbreviation for \"power of hydrogen\".\r\n" );
document.write( "\r\n" );
document.write( "The pH scale was defined because the enormous range of hydrogen ion\r\n" );
document.write( "concentrations found in aqueous solutions make using H+ molarity awkward.\r\n" );
document.write( "For example, in a typical acid-base titration, [H+] may vary from about\r\n" );
document.write( "0.01 M to 0.0000000000001 M. It is easier to write \"the pH varies from \r\n" );
document.write( "2 to 13\". \r\n" );
document.write( "\r\n" );
document.write( "The hydrogen ion concentration in pure water around room temperature is about\r\n" );
document.write( "1.0 × 10-7 M. A pH of 7 is considered \"neutral\", because the concentration of\r\n" );
document.write( "hydrogen ions is exactly equal to the concentration of hydroxide (OH-) ions\r\n" );
document.write( "produced by dissociation of the water. Increasing the concentration of hydrogen\r\n" );
document.write( "ions above 1.0 × 10-7 M produces a solution with a pH of less than 7, and the\r\n" );
document.write( "solution is considered \"acidic\". Decreasing the concentration below 1.0 × 10-7\r\n" );
document.write( "M produces a solution with a pH above 7, and the solution is considered \"alkaline\" or \"basic\". \r\n" );
document.write( "\r\n" );
document.write( "pH is often used to compare solution acidities. For example, a solution of \r\n" );
document.write( "pH 1 is said to be 10 times as acidic as a solution of pH 2, because the\r\n" );
document.write( "hydrogen ion concentration at pH 1 is ten times the hydrogen ion concentration\r\n" );
document.write( "at pH 2. This is correct as long as the solutions being compared both use the\r\n" );
document.write( "same solvent. You can't use pH to compare the acidities in different solvents\r\n" );
document.write( "because the neutral pH is different for each solvent. For example, the\r\n" );
document.write( "concentration of hydrogen ions in pure ethanol is about 1.58 × 10^-10 M, so\r\n" );
document.write( "ethanol is neutral at pH 9.8. A solution with a pH of 8 would be considered\r\n" );
document.write( "acidic in ethanol, but basic in water! \r\n" );
document.write( "\r\n" );
document.write( "Edwin
\n" ); document.write( "
\n" );