Amphiprotic/Amphoteric Nature of HSO4- & H2PO4 - ChemistryHelp.net

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In summary, HSO4- and H2PO4- are both considered amphiprotic substances because they have the ability to both accept and donate H+ ions, despite being the conjugate bases of strong acids. This is due to the fact that the equilibrium for their ionization is not completely favored towards one side, unlike the case for H2SO4.
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aonin
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Hey guys, on http://www.chemistryhelp.net/basic-chemistry/amphiprotic-substances

I saw that HSO4- (hydrogen sulfate) is a amphiprotic (can accept and donate H+ ions) and therefore acts as a base or acid (amphoteric)

why is this so? Isn't H2SO4 (sulfuric acid) a strong acid and so its equilibrium completely favours the ionisation into HSO4-, therefore HSO4- cannot accept H+ ions to reform back into H2SO4

similarly this happens for H2PO4 (Dihydrogen phosphate ion), so why is it listed as amphiprotic even though H3PO4 is a strong acid and the equilibrium would completely favour ionisation into H2PO4?

So, why are these 2 ions listed as amphoteric even thought they are the weak conjugate bases of strong acids (LB theory)?

Thanks
 
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You shouldn't believe everything you read on the internet, especially when it contradicts your own understanding.
 
  • #3
aonin said:
I saw that HSO4- (hydrogen sulfate) is a amphiprotic (can accept and donate H+ ions) and therefore acts as a base or acid (amphoteric)

why is this so? Isn't H2SO4 (sulfuric acid) a strong acid and so its equilibrium completely favours the ionisation into HSO4-, therefore HSO4- cannot accept H+ ions to reform back into H2SO4

similarly this happens for H2PO4 (Dihydrogen phosphate ion), so why is it listed as amphiprotic even though H3PO4 is a strong acid and the equilibrium would completely favour ionisation into H2PO4?
H2SO4 has Ka1 ~ 10^6, but H3PO4 has Ka1 of only about 10^-2. So I think that statement is at least somewhat reasonable for H2PO4-.
 

Related to Amphiprotic/Amphoteric Nature of HSO4- & H2PO4 - ChemistryHelp.net

1. What is the amphiprotic/amphoteric nature of HSO4- and H2PO4-?

The amphiprotic/amphoteric nature of a substance means that it can act as both an acid and a base. In the case of HSO4- and H2PO4-, they both have the ability to donate a proton (acting as an acid) or accept a proton (acting as a base).

2. How do HSO4- and H2PO4- exhibit amphiprotic/amphoteric properties?

HSO4- and H2PO4- have a hydrogen atom bonded to an oxygen atom, which is responsible for their amphiprotic/amphoteric behavior. The hydrogen atom can either lose or gain a proton, depending on the pH of the solution.

3. Are HSO4- and H2PO4- considered weak or strong amphiprotic/amphoteric substances?

Both HSO4- and H2PO4- are considered weak amphiprotic/amphoteric substances. This means that they do not completely dissociate in water and have a limited ability to donate or accept protons.

4. How does the amphiprotic/amphoteric nature of HSO4- and H2PO4- affect their acid-base behavior?

The amphiprotic/amphoteric nature of HSO4- and H2PO4- allows them to act as buffers in a solution. This means that they can resist changes in pH by donating or accepting protons to maintain a relatively stable pH.

5. What are some common uses of HSO4- and H2PO4- in everyday life?

HSO4- and H2PO4- are commonly found in household cleaning products, such as detergents and soaps. They are also used in fertilizer and food production. In addition, H2PO4- is an important component in dental products, such as toothpaste, due to its ability to prevent tooth decay.

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