base and acids

[405672459]

How can you determine if a base is weak or strong?

[Rebecca_Park_1G]

Weak bases do not fully dissociate while strong bases do. As such, a Kb value for weak bases will be given, while strong bases will never have a Kb value since there is 100 percent dissociation. Strong bases include those with Group 1 and 2 cations. Anything outside that list is a weak base I believe, but I could be wrong.

[Louis_Wong_3I]

The strong acids are HCl, HBr, HI, H2SO4, HNO3, HClO4, HClO3. The strong bases are Group 1 and Group 2 hydroxides (ex. NaOH, Ca(OH)2) and Group 1 and Group 2 oxides (ex. Na2O, MgO).

[Carissa Liu 3A]

Strong bases fully dissociate, so the reaction strongly favors the products. Therefore, expect the Kb values to be large, and the pKb values to be small. Many strong bases consist of group 1 or 2 cations bonded with either hydroxide (OH) or oxygen (O) to form metal hydroxides or metal oxides.
Weak bases do not fully dissociate, so the reaction strongly favors the reactants. Therefore, expect the Kb values to be very small, and the pKb values to be large. Many weak bases consist of a nitrogen atom that has a lone pair of electrons.

[Peter_Wisner_3F]

Strong acids and bases fully dissociate in a solution and there are only a known handful of each.

Weak acids and bases only partially dissociate in a solution such that there are molecules of both the original acid/base and the conjugate base/acid at the same time. The extent to which a weak acid or base dissociates is given with a K value.

[Erin Haisan 1B]

Hello! When we are given a Ka or Kb value, it is implied that the acid or base is weak. Another rule of thumb is the strong bases are metal hydroxides (OH-) and metal oxides (O2-). Additionally, when the Ka value is small, less product is formed, meaning that the acid used in the reaction is weak. However, a strong acid will have a lower pKa value but a high Ka value; thus, keep this in mind when ranking acids' strength.

[Cameron Tran 3E]

In terms of molecules, there are only a certain amount of strong acids and bases. The others in the forum mentioned some, but you can find them online too. Any other molecule besides those is going to be weak acids or bases.

[Joan Thyagarajan 2G]

You can determine if a base is weak based on its percentage decomposition. If a substantial amount of the base does not dissociate then you can assume it is a weak base. I believe Dr. Lavelle pointed out that if the K constant is less than 10^-3 it could be considered a weak base.

[joannar]

Hi! So strong bases can be found in the periodic table and they are The hydroxides of the Group I (alkali metals) and Group II (alkaline earth). In terms of weak bases, I believe like the other previous responses mentioned the kb values would be expected to be very small meaning they did not fully dissociate

[jenna koerner 2E]

In reactions, strong bases fully dissociate while weak bases do not fully dissociate. Strong bases have more basic pHs while weak bases have lower pHs. Strong bases are oxides with Group 1 and 2 on the periodic table while weak bases are all other bases.

[Ava Ward 1K]

The trick to determining whether an acid or base is strong or weak is if it fully dissociates or not. There is a list of specific strong acids and bases which tell you that they all dissociate completely in water. However if a weak acid or base is added to a water solution, it will not fully dissociate. The pH is also a determining factor because strong acids and bases have pHs closer to their designated end of the pH scale.

[105897549]

Hi!
To determine if the acid or base is weak or strong, I would first remember the most common strong acids and bases and if they are not on the list, then it is most likely that they are weak. However, you can also analyze the Ka and pKa values. Higher Ka values and lower pKa values are associated with stronger acids and bases. The pKa of a strong acid is generally less than 0. Best of luck!

[Valerie Jun 2D]

I think in general strong acids are the ones that contain elements from the furthest right side on the periodic table

[Carmen Lo 1L]

Hi! I think the easiest way to know if a base is strong or not is to remember the strong bases. The first and second column of the periodic table is where the strong bases are. In the first column the bases have an OH (ex: LiOH, KOH...) and the second column, the bases have (OH)_2 (ex: Ba(OH)_2,Ca(OH)_2...). I hope this helps!