An oxalic acid solution contains the following species in varying concentrations: H2C2O4, HC2O4-, C2O4^2-, and H+. Which of the above four species can act only as acids, which can act only as bases, and which can act as both acids and bases?
To determine which species can act as acids or bases, we need to understand their behavior in terms of donating or accepting protons (H+ ions). Let's analyze each species:
1. H2C2O4 (oxalic acid): This compound can act as an acid because it can donate a proton (H+ ion) from its acidic –COOH group.
2. HC2O4- (hydrogen oxalate ion): This ion can act as both an acid and a base. It can donate a proton from its acidic -COOH group or accept a proton to form oxalic acid (H2C2O4).
3. C2O4^2- (oxalate ion): This ion can act as a base because it can accept a proton (H+) to form the hydrogen oxalate ion (HC2O4-).
4. H+ (Hydrogen ion): This ion can act as an acid because it can donate a proton (H+).
In summary:
- H2C2O4 can act only as an acid.
- HC2O4- can act both as an acid and a base.
- C2O4^2- can act only as a base.
- H+ can act only as an acid.
Remember, the behavior of acids and bases depend on their ability to donate or accept protons, respectively.
To determine which species can act only as acids, only as bases, or both as acids and bases, we need to consider their behavior in chemical reactions and their ability to donate or accept protons (H+ ions).
1. H2C2O4 (oxalic acid): This compound can act as both an acid and a base. It can donate a proton (H+) to a base, making it an acid. It can also accept a proton (H+) from an acid, making it a base.
2. HC2O4- (hydrogen oxalate or hydrogen oxalate ion): This species can also act as both an acid and a base. It can donate a proton (H+) to a base, hence acting as an acid. It can also accept a proton (H+) from another acid, making it a base.
3. C2O4^2- (oxalate ion): This species can only act as a base. It can accept a proton (H+) from an acid, making it a base.
4. H+ (hydrogen ion): This species can only act as an acid. It can donate a proton (H+) to a base, making it an acid.
Therefore, H2C2O4 and HC2O4- can act as both acids and bases, C2O4^2- can act only as a base, and H+ can act only as an acid.
You need to apply the definition. I assume you are using the Bronsted-Lowry theory. Acids donate a proton; bases accept a proton.
H2C2O4, for example, can ONLY donate a proton (you know there is no such thing as H3C2O4 or H4C2O4) so it looks like this. H2C2O4 ==> H^+ + HC2O4^-. Another for example is that HC2O4^- can act as both an acid and a base. WHY? Because it can donate a H^+ as in HC2O4^- ==> H^+ + C2O4^2- (the fact that H^+ and C2O4^2- are listed in the same question should tell you that those exist so it can go to the right and act as an acid OR it can do HC2O4^- + H^+ ==> H2C2O4 and act as a base.) That takes care of two of them; I'll leave the other two for you.