How to determine whether a compound is acidic or basic

[annemarielawrence]

When trying to figure out if a compound is acidic or basic, when is it best to draw the Lewis structures and when is it better to separate the compound into it's ions?

[Lily Dabrowski 2G]

I think it's always better to just look at what is making up the compound, including the ions. The general rule of thumb is that an acid is going to donate an H+ ion while a base is going to accept it. For acids: if the compound starts with H or ends in COOH, it's probably an acid. Strong acids are almost completely ionized in water, so if the compound is mixed in water, it will form H3O+ and an anion. Must have an H somewhere. For bases: if the compound is formed from a group 1 or 2 element (cation) with an (OH), it's a strong base. If it has a nitrogen with a lone pair, it'll be a weak base. Strong bases are also completely ionized in water, so it'll form OH- and a cation. Drawing out the lewis structures can be helpful in deciding where an H may transfer to/from, but I find these rules above more helpful.

[Jessica Arcos 2H]

Adding to what the person above said, I would just suggest remembering that a strong base and weak acid make a basic compound, strong acid and weak base make an acidic compound, and a strong acid with a strong base makes a neutral compound.

[Violet Mbela 2B]

I think it's always better to just look at what is making up the compound, including the ions. The general rule of thumb is that an acid is going to donate an H+ ion while a base is going to accept it. For acids: if the compound starts with H or ends in COOH, it's probably an acid. Strong acids are almost completely ionized in water, so if the compound is mixed in water, it will form H3O+ and an anion. Must have an H somewhere. For bases: if the compound is formed from a group 1 or 2 element (cation) with an (OH), it's a strong base. If it has a nitrogen with a lone pair, it'll be a weak base. Strong bases are also completely ionized in water, so it'll form OH- and a cation. Drawing out the lewis structures can be helpful in deciding where an H may transfer to/from, but I find these rules above more helpful.

When you use the reaction method to determine, how do you know whether you end up with H30+ or OH-?