Identifying Bases

[Brendan Duong 1I]

From Fundamentals J.1
How can we distingish
KOH and Ca(OH)2 as bases?
Are all compounds with OH bases or is it more complicated than that?

[Aaron Akhavan-Dis1B]

Bases in water produce hydroxide ions (OH^-), but don't necessarily need to have OH in its formula to be called a base. For example KOH, Ca(OH)₂, NaOH, Mg(OH)₂ all have OH and are bases. There are some bases that don't have OH but look like CaO, Li₂O, CH₃NH₂ that are all bases. As long as the result of the base + H20 leads to a cation and OH- then it is a base.

[Jay Solanki 3A]

Usually, bases are compounds that create hydroxide (OH-) in solution. One way that compounds do this is by releasing OH- into the solutions, as explained by the strong bases you listed above. Another way this occurs is if a compound removes a hydrogen ion (H+) from water. One example of this is ammonia (NH3), which has a lone pair and can therefore donate its lone pair in an effort to remove a Hydrogen ion from a water molecule, leaving OH- remaining in the solution. This occurs with other bases of salts as well, such as acetate. Hope this helps!

[Lily Kiamanesh 2G]

With the Bronsted-Lowry definition of a base, it is a species that is capable of accepting a proton. With the two examples you gave, the species dissociate, producing a cation and a hydroxide ion. The hydroxide ion with its 1- charge is capable of pulling protons away from water molecules, producing more OH- in solution. I believe this contribution of OH- defines them as bases.

[Brendan Duong 1I]

With the Bronsted-Lowry definition of a base, it is a species that is capable of accepting a proton. With the two examples you gave, the species dissociate, producing a cation and a hydroxide ion. The hydroxide ion with its 1- charge is capable of pulling protons away from water molecules, producing more OH- in solution. I believe this contribution of OH- defines them as bases.

How do we know they will disassociate in water to produce OH and a cation?

[Lily Kiamanesh 2G]

The two bases you stated are strong bases, meaning that they will dissociate completely into their ionic components. Their components are a cation and hydroxide ion(s). Hope this helps!

[Madeline Louie 1B]

Is there a quick way to identify a strong base from a weaker base? Like if it has an OH in it (for example, KOH) does that indicate anything as compared to a molecule without an OH (like CaO)?

[Isabella Chou 1A]

Is there a quick way to identify a strong base from a weaker base? Like if it has an OH in it (for example, KOH) does that indicate anything as compared to a molecule without an OH (like CaO)?

Strong bases are group 1 and group 2 oxides and hydroxides. For example, LiO2, NaOH, CaO, and Mg(OH)2 are some strong bases. If the bases do not fall under this description, then they are weak bases. To compare the relative strength of bases, you can also compare the Kb (basicity constant) values of the two bases.