How do you know that HNO3 diss
How to tell whether a substance is an acid or a base depending on its chemical formula. I know that it depends on how it dissociates; a chemical is an acid if it dissociates into a H+ and a base if it dissociates into a OH-.
But how do you know what it dissociates into? How do you know that HNO3 dissociates into H+ and NO3- making it an acid?
How do you know that CH3NH2 is the base and CH3NH3+ is the conjugate acid for use in the Hendersen Hasselbach equation?
Answer:
first, elt us define acid/(bases
Arrhenius Acid/Base
Arrhenius acid/base is the first theory on acid/basedefinitions, it is mostly true for general applications.
Arrhenius acid is any type of substance that will dissociate inwater to form hydrogen ions [H+]. That is, an acid increases theconcentration of H+ ions in an aqueous solution.
Arrhenius base is any type of substance that will form hydroxide[OH−] ions. It typically must increase pH since OH- increases inconcentration.
Examples of Arrhenius acid
HCl, H2SO4, H3PO4 à they will donate 1, 2, and 3 protons tosolution i.e. H+
Examples of Arrhenius base
NaOH, Ca(OH)2, and; avoid NH3, since it is basic, yet will notdonate OH from its NH3 equation.
Bronsted Lowery Acid/Bases
First, let us define Bronsted Lowry acid/base:
Bronsted Lowry acid: any species that will donate H+ (protons)in solution, and makes pH lower (i.e HCl)
Bronsted Lowry base: any species that will accept H+ (protons)in solution, and makes pH higher (NH3 will accept H+ to formNH4+)
Typically, acid/bases are shown in the left (reactants)
when we write the products:
Bronsted Lowery conjugate base = the base formed when the B.L.acid donates its H+ proton ( i.e. HCl ->Cl-
Bronsted Lowery conjugate acid = the acid formed when the B.L.base accept its H+ proton ( i.e. NH4+ has accept H+ proton)
Note that, typically conjugate bases/acids are shown in theright (product) side
So, from your reaction:
H2Y- transforms to H3Y; it is gaining and H+, so it is aBASE
H2Z- transforms to HZ2-; it is losing H+, so it is an ACID
then,
H3Y is the conjugate ACID (since it could donate H+ to formH2Y-)
and HZ2- is the conjugate BASE ( since it could accept H+ toform H2Z-)
now…
Typically, you need to KNOW the reactions
NO3 –> nitrate, NO3- is very electrnoegative since both, Nand O are electongative, they will dissocaite H+ readily.
Then, CH3NH2 is an amine, if you see, the only electronegativespecies is Nitrogen, no other
then
NH2 group can accept H+ since nitrogen ahs a lone pair
therefore,
amines are most likely to act as a base
special note…
theoretically speaking,
NH3 is a base, but will act as an acid if NH3 –> NH2- + H+is formed, which “typically” we will not see, but it mighthappen…. As well
NH2- wil act as a base, to accept H+ , stronger than NH3