![]() Water is very, very weakly acidic methane is not really acidic at all. Methane is not really an acid at all, and it has an estimated pKa of about 50.įigure AB9.4. Water can certainly give up a proton, but not very easily it has a pKa ofĪround 14. Their pKas are reported as 4.76 and 3.77, ![]() On the other hand, acetic acid (found in vinegar) andįormic acid (the irritant in ant and bee stings) will also give up protons, but Nitric acid in water has a pKa of -1.3 and hydrobromicĪcid has a pKa of -9.0. Some Bronsted acidic compounds these compounds all supply protons relativelyįor example, nitric acid and hydrochloric acid both High pKa means a proton is held tightly.pKa can sometimes be so low that it is a negative number!.Low pKa means a proton is not held tightly.Proton is held, and the less easily the proton is given up. The higher the pKa of a Bronsted acid, the more tightly the The lower the pKa of a Bronsted acid, the more easily it gives Small, negative number, such as -3 or -5. PKa measures how tightly a proton is held by a Bronsted acid. This experimental parameter is called "the pKa". Someone has done the work to measure how tightly the proton is bound.Įxperimental in this sense means "based on physical evidence". Often implies to students "untested" or "unreliable", but here it means that Tells us how tightly protons are bound to different compounds. There is an experimentally-determined parameter that If we know which sitesīind protons more tightly, we can predict in which direction a proton will beĭirection will the equilibrium lie? Which base gets the proton? That binds protons less tightly will lose the proton. Site that binds the proton more tightly will retain the proton, and the site Involves being passed from a more acidic site to a less acidic site, then the Bronsted-Lowry acidities of different compounds.
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