Textbook Question 6A.17

[Eliana Carney 3E]

Hey guys! I'm kinda confused on how to determine wether or not a compound is acidic, basic, or amphoteric. If someone could explain to me why, in question 6A.17, BaO is basic, SO3 is acidic, and As2O3 and Bi2O3 are ampotheric that would be great. Also, if there are any guidelines for determining if a compound is acidic, basic, or amphoteric and you could include them in your explanation, that would be awesome. Thanks in advance!

[Kaylee Messick 3J]

In the textbook, in Section 6A.3, it discusses oxides. It states that usually if there is a metal, it will be basic and if there is a nonmetal, it will be acidic. It also lists examples of amphoteric compounds. Hope this helps!

[Marcus Lagman 2A]

Hello!

BaO is considered to be a basic oxide because it accepts protons (Hydrogen) from water to form a solution of Hydroxide ions. Producing OH- is a very basic characteristic.

SO3 is considered to be an acidic oxide because it reacts with water to form a Bronsted Acid (H2SO4). Not only that, but acidic oxides can also react with bases to form salts. This process is more complicated as a hydroxide (OH-) from H2O first attacks SO3 creating HSO4- and then the HSO4- transfers its proton (H+) back to a hydroxide ion (OH-) to produce water.
This is the equation: SO2 + 2NaOH → HSO3- + 2Na+ + OH- → Na2SO3 + H2O

As2O3 and Bi2O3 are amphoteric because they can both react with acids and bases.

A good guideline is to look at the periodic table. Acidic oxides contain nonmetals like Sulfur, Basic oxides contain metals like Barium, and amphoteric oxides contain elements on the diagonal line from Beryllium towards Polonium and several metals from the d-block.

I hope this helps!