Acids and Bases

Moderators: Chem_Mod, Chem_Admin

Joanna Pham - 2D
Posts: 113
Joined: Fri Apr 06, 2018 11:04 am

Acids and Bases

Postby Joanna Pham - 2D » Mon Jan 14, 2019 4:21 pm

I haven't taken Chem 14A in a long time, so I don't remember how to figure out if an acid/base is strong or weak. Can someone please explain how you could determine if an acid or base is strong or weak without being given the chemical equation?

Also, in class,the Professor did an example where we had to find the moralities of H3O+ and OH- if there was .0030 mol/L of Ba(OH)2. How would you know that Ba(OH) is a strong base or weak base based on this information only and how would I know how to write the chemical equation for this as well?

Thanks!
Last edited by Joanna Pham - 2D on Mon Jan 14, 2019 4:27 pm, edited 1 time in total.

AdityaGuru1H
Posts: 65
Joined: Fri Sep 28, 2018 12:17 am

Re: Acids and Bases

Postby AdityaGuru1H » Mon Jan 14, 2019 4:27 pm

you basically have to memorize them. Feel free to correct me but I think the list is (there may be a few more bases but i am not 100% sure)
Acids: HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4
Bases: LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

fgalasso1b
Posts: 32
Joined: Wed Oct 03, 2018 12:15 am

Re: Acids and Bases

Postby fgalasso1b » Mon Jan 14, 2019 4:28 pm

We had to memorize our Strong Acids and Bases which are
HCl - hydrochloric acid
HNO3 - nitric acid
H2SO4 - sulfuric acid (HSO4- is a weak acid)
HBr - hydrobromic acid
HI - hydroiodic acid
HClO4 - perchloric acid
HClO3 - chloric acid.

Potassium hydroxide (KOH)
Sodium hydroxide (NaOH)
Barium hydroxide (Ba(OH)2)
Caesium hydroxide (CsOH)
Strontium hydroxide (Sr(OH)2)
Calcium hydroxide (Ca(OH)2)
Lithium hydroxide (LiOH)
Rubidium hydroxide (RbOH)

Any other acid/base is weak.

Danielle_Gallandt3I
Posts: 70
Joined: Fri Sep 28, 2018 12:24 am

Re: Acids and Bases

Postby Danielle_Gallandt3I » Mon Jan 14, 2019 5:54 pm

A good rule of thumb for strong bases is that the cation of the base is typically in the first or second group within the periodic table.

Michelle Fu 1H
Posts: 35
Joined: Fri Sep 28, 2018 12:19 am

Re: Acids and Bases

Postby Michelle Fu 1H » Mon Jan 14, 2019 5:56 pm

While it is good to memorize specifically which are acids and bases, there are a couple of indicators for just figuring it out yourself
Strong acids: Generally a H+ ion with a nonmetal with a large radius, such as HCl or HBr, oxyacids (acids with oxygen) with more oxygen (for example, HNO3 is a stronger acid than HNO2), elements with a strong charge (+3 or more such as Al3+)

Weak acids: H+ with a nonmetal with a small radius, such as HF

Strong bases usually have H-, OH- or O-2

Note that the conjugate bases of strong acids (which is Cl out of H, or Br- out of H) are neutral, as are alkaline metals such as Na+.

Melody P 2B
Posts: 35
Joined: Fri Sep 29, 2017 7:06 am

Re: Acids and Bases

Postby Melody P 2B » Mon Jan 14, 2019 5:56 pm

Then is there no way to determine whether an acid or base is strong by just looking at the compound itself? It's just memorization?

Christina Chang 1C
Posts: 34
Joined: Thu May 10, 2018 3:00 am

Re: Acids and Bases

Postby Christina Chang 1C » Mon Jan 14, 2019 11:36 pm

From looking at a reaction, if it dissociates fully and forms a salt and water then that would be another way to recognize a strong acid or a strong base.

Ashley Kim
Posts: 62
Joined: Fri Sep 28, 2018 12:19 am
Been upvoted: 1 time

Re: Acids and Bases

Postby Ashley Kim » Tue Jan 15, 2019 12:26 am

You can also tell from the pKa of the reaction. The smaller the pKa value, the stronger the acid.


Return to “Equilibrium Constants & Calculating Concentrations”

Who is online

Users browsing this forum: No registered users and 2 guests