How to tell if a compound is a strong or weak acid/base

[trishaferrer]

Hello! How can you tell if a compound is a strong or weak acid or base just by looking at it?

[Jessica Ghiuzelian 1H]

Hi! I usually look for the charge of the compound, so for bases they tend to be negatively charged since they donate the electron pair, and acids would be positively charged since they accept the electron pairs. This is not always true, so I would still try to find if an electron pair is being donated or accepted, and if H3O+ or OH- is being produced.

[Aaron Li 1D]

You will need to memorize the strong acids, which are HCl, HBr, HI, H2SO4, HNO3, HClO4, and HClO3. All other acids are considered weak acids. For bases, the strong bases are group 1 and 2 cations that are hydroxides or oxides. For instance, K is a group 1 cation, so when combined with a hydroxide, OH-, it forms a strong base. All other bases will be considered weak bases.

[Amy Jordan 2A]

Hi,
First, memorizing the strong acids and strong bases is super helpful. Some other tricks are for oxyacids the acid that has more oxygens is stronger (ex. HClO4 is stronger than HClO3 and HClO2). Also, a weaker bond makes it easier for the proton to come off which results in a stronger acid. For binary acids like HI, HBr, HCl, HF, etc the acid gets stronger as the element other than H increases down the periodic table, so HI>HBr>HCl>HF (Hopefully this makes sense). Acids in general tend to begin with H as well or they end with COOH.
Molecules with N and one lone pair are usually weak bases, and strong bases contain a metal cation and OH (ex. LiOH or NaOH). I hope this helps!

[SerenaSabedra]

Your best bet is to memorize the strong acids and bases, however, there are some general rules that may be more helpful. Stronger acids will contain more electronegative atoms such as F, Cl, or O to help stabilize the resulting anion. Another general rule is bond length of the A-H bond. A weaker, longer bond will make a stronger acid because it more readily loses its proton.

[205819952]

Group 1 and 2 cations that are hydroxides or oxides are strong bases. All other bases will be regarded as weak.

[205678283]

You can look at the atoms in terms of where they are on the periodic table, and use trends to help you figure out which is a stronger acid. Stronger acids will lose H+ more easily. Therefore, if we are looking at HF or HCL, we can see that HCL is a stronger acid because the HCl bond is longer, weaker, and will break more easily. Also, if there are more lone oxygens in a molecule, the electrons will be more delocalized with resonance and so the anion is more stable and so the acid is stronger. For example, HClO2 is a stronger acid than HClO. We can also look at electronegativity. For example, HClO4 is a stronger acid than H3PO4 even though there are 4 oxygens in each because Cl is much more electronegative than P o=so it can pull the electrons more and increase the polarity of the O-H bond.

[Neha Jonnalagadda 2D]

There are some compounds that just need to be memorized in terms of common acids and bases. Otherwise you should look for signs that impact how the compound will dissociate. If the compound dissociated easily in an aqueous state, then it is normally a strong acid or base and if it doesn't then it is a weaker acid or base.

[Rebekah Han 2K]

For the strong acids, you kind of just have to memorize what they are. There are 7: HCl, HBr, HI, HNO3, H2SO4, HClO3, and HClO4. Anything other than that is a weak acid. Typically, acids have an H in them. For strong bases, its typically group 1 and 2 hydroxides and oxides. Also, for a weak base, if there is a nitrogen with lone pairs, it's a good indicator that that is a weak base.

[Gavin Trent 2F]

The easiest thing to do is to memorize the strong acids and bases, that way you will immediately know when an acid/base is weak. I would recommend making a quizlet to memorize these really quickly.

[Tammy Shen 2L]

You'll have to memorize the strong acids and bases, since those are a set list that don't change. Then, you need to identify if the compound is an acid or base. You can usually do this easily as acids will often have an H and bases often have an OH.