What is an oxyacid?

Question

What is an oxyacid?

Luna Chen · Accepted Answer

It is an acidic substance in which one or more hydrogen atoms are bonded to oxygen atoms that are on turn bonded to another element "#X#": #X-O-H#.

An acid is a substance which is able to donate protons (#H^+#). In the case of an oxyacid, #XOH#, this ability is due to the high electron withdrawing effect of the #XO# group upon the hydrogen atom, as describet in detail in the following. The element X is an electronegative nonmetal, as #N, S, Cl# etc. or a high oxidation state metal, as #Mn(VII)# or #Cr(VI)#. Then, helped by the high electronegativity of the oxygen atom, the couple #XO"-"# causes a withdrawing effect on the electron pair of the #O-H# bond. The proton (#H^+#), at the end of chain, is partially unshielded and ready to be transferred to bond an electron pair furnished by a basic species. This process is called ionisation and leaves an oxoanion, #XO^-# as the residue of the oxyacid. Thus, the entire proton transfer or acid-base process is: #XOH + :B^"-" -> XO^"-" + H:B# Example with nitric acid (#HNO_3 = O_2NOH#, where #X = O_2N#) and hydroxide ion as base: #HNO_3 + :OH^"-" -> NO_3^"-" + H_2O# Using ammonia as the base and nitric acid as the example #HNO_3 + :NH_3 -> NO_3^"-" + NH_4^+# In some cases the central element is not highly electronegative, but it gains withdrawing effect by its bonds with extra oxygen atoms, as in carbonic acid (#H_2CO_3 = OC(OH)_2#), phosphoric acid, #H_3PO_4 = OP(OH)_3#, phosphonic acid #H_3PO_3 = OPH(OH)_2#. Generally speaking, an oxyacid is stronger (i.e., more easily ionizable) the more extra oxygen atoms it contains. There are numerous examples that support this, including: a) nitric acid #HNO_3 = O_2NOH# is stronger than nitrous acid #HNO_2 = ONOH# b) sulfuric acid #H_2SO_4 = O_2S(OH)_2# is stronger than sulfurous acid #H_2SO_3 = OS(OH)_2# c) The sequence's chlorine oxyacids are more potent: #HClO < HClO_2 < HClO_3 < HClO_4# that is: #ClOH < OClOH < O_2ClOH < O_3ClOH# or, given name: Acids: hypochlorous, chlorous, chloric, and perchloric

Naomi Aronson · Answer

undefined An oxyacid is a type of acid that contains oxygen, along with hydrogen and another element. Oxyacids are named based on the element they contain and are known for their ability to donate protons in a chemical reaction. Examples include sulfuric acid (H2SO4) and nitric acid (HNO3).