# Why Do My Amphoteric Equations Keep Going Wrong?

• paperdoll
In summary, amphoteric acids and bases are substances that can act as both an acid and a base, depending on the conditions they are in. Examples include water, amino acids, aluminum hydroxide, zinc oxide, and aluminum oxide. In water, amphoteric acids can donate a proton and behave as acids, while amphoteric bases can accept a proton and behave as bases. They are different from amphiprotic substances in that they can act as both an acid and a base, while amphiprotic substances can only donate or accept protons. Amphoteric acids and bases can be identified in a chemical reaction by their ability to act as both an acid and a base, changes in pH, and the presence of
paperdoll

## Homework Statement

I'm having problems understanding amphoteric acids and bases. I know amphoteric means that it can act as an acid or base, but when the question asks me to write the equation to support this statement, I always get it wrong

## Homework Equations

HSO4^-1 is an amphotheric ion. Write chemical equations to show this ion acting as
a) an acid
b) a base

## The Attempt at a Solution

For a)
I wrote HSO4^-1 + H2O -> SO4^-2 + H3O^+
but, on the answers it is HSO4^-1+OH^-1 -> SO4^-2 + H2O

For b) I wrote HSO4^-1 + H2O -> H2SO4 + OH^-1
but on the answers it is HSO4^-1 + H3O+ ->H2SO4 + H2O

I have no idea why I'm wrong Could someone help explain this to me?

I don't think you are wrong, your answers make sense to me.

Borek said:
I don't think you are wrong, your answers make sense to me.

oh hm :shy:. So is my answer and the book's answer both correct? I'm a bit worried since I have an acids and bases test coming up.

I think what the test is looking for is for the neutralisation reaction between an acid and alkali. It would be better to phrase it such that it shows the ion reacting with a hydroxide ion for the acidic property and the basic ion for the basic property.

Both of your equations also have the same reagents. Since water can self-ionise to form hydronium and hydroxide ions and those are the ones reacting, it is wrong to write water as the water is not the ion reacting with the bisulphate ion.

Both are correct - both show that HSO4- behaves like an acid and like a base. The difference is that you show it can yield both H+ and OH- when put in solution, while they show it can react with H+ and OH-. These are equivalent statements (more precisely - equivalent enough for a purpose of showing HSO4- is amphoteric).

There is a reason why the book answer to b is better - H2SO4 is a very strong acid, chances of observing HSO4- reacting with water molecule to produce OH- are slim. It will be easier to desing an experiment in which HSO4- can be protonated to H2SO4. That's all in dissociation constants and reaction equilibrium. But it doesn't make your answer wrong, at least IMHO.

Borek said:
Both are correct - both show that HSO4- behaves like an acid and like a base. The difference is that you show it can yield both H+ and OH- when put in solution, while they show it can react with H+ and OH-. These are equivalent statements (more precisely - equivalent enough for a purpose of showing HSO4- is amphoteric).

There is a reason why the book answer to b is better - H2SO4 is a very strong acid, chances of observing HSO4- reacting with water molecule to produce OH- are slim. It will be easier to desing an experiment in which HSO4- can be protonated to H2SO4. That's all in dissociation constants and reaction equilibrium. But it doesn't make your answer wrong, at least IMHO.

ooh okay

so then in the case of HCO^-3, to show it is a base, it would be HCO3^-1 + H3O+ -> H2CO3 + H2O?

paperdoll said:
so then in the case of HCO^-3, to show it is a base, it would be HCO3^-1 + H3O+ -> H2CO3 + H2O?

Yes.

In this case, as H2CO3 is a weak acid, reaction with water:

HCO3- + H2O <-> H2CO3 + OH-

is quite common, so it will be as good as the one you wrote.

## 1. What are amphoteric acids and bases?

Amphoteric acids and bases are substances that have the ability to act as both an acid and a base, depending on the conditions they are in. This means that they can donate or accept protons (H+) in a chemical reaction.

## 2. What are some examples of amphoteric acids and bases?

Examples of amphoteric acids include water (H2O), amino acids, and aluminum hydroxide. Amphoteric bases include zinc oxide, aluminum oxide, and certain metal hydroxides.

## 3. How do amphoteric acids and bases behave in water?

In water, amphoteric acids can donate a proton to water molecules, making them behave as acids. On the other hand, amphoteric bases can accept a proton from water molecules, making them behave as bases.

## 4. How are amphoteric acids and bases different from amphiprotic substances?

Amphoteric acids and bases are substances that can act as both an acid and a base, while amphiprotic substances are substances that can donate or accept a proton in a chemical reaction. This means that all amphoteric substances are amphiprotic, but not all amphiprotic substances are amphoteric.

## 5. How can amphoteric acids and bases be identified in a chemical reaction?

Amphoteric acids and bases can be identified in a chemical reaction by their ability to act as both an acid and a base. This can be seen through changes in their pH, as well as the products formed in the reaction. Additionally, amphoteric substances will have both acidic and basic functional groups in their chemical structure.

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