Strong Acid and Base

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MinjooPark_3I
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Strong Acid and Base

Postby MinjooPark_3I » Fri Jan 15, 2021 5:08 pm

Hi, I was having a hard time trying to understand solving for pH/pOH of strong acids and bases. So, I understand that when there is a strong acid or base, it will completely dissociate, so we will have to write a new equation or make a second ICE table but I do not understand why the dissociation makes the H+ or the OH- have a molar concentration. I dont know if my question makes sense... but thank you for your help!

Eve Gross-Sable 1B
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Re: Strong Acid and Base

Postby Eve Gross-Sable 1B » Fri Jan 15, 2021 5:22 pm

Hi! I am not sure what you mean by writing a new equation or making a second ICE table, typically there should just be one for these problems. But aside from that, when dissociation occurs, it means that the strong acid or base completely separates into its ions when it is in water. Therefore, H+ (for strong acids) and OH- (for strong bases) must have a molar concentration because the compound itself has broken down into pieces.

So for example (from lecture) if you had .0030M Ba(OH)2 at 25C, it will completely ionize in liquid water because it is a strong base. The equation is
Ba(OH)2 (solid) -> Ba2+ (aqueous) + 2OH- (aqueous)
As you can see, the OH- must have a molar concentration.
I hope this helps a bit!

Mackenzie Van Val 3E
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Re: Strong Acid and Base

Postby Mackenzie Van Val 3E » Fri Jan 15, 2021 7:21 pm

Hi! As the commenter above said, the H+ or OH- comes from the dissociation of the strong acid or the strong base. Just like the dissociation of NaCl in water would cause both Na+ and Cl- ions to form, when a strong acid like HCl dissociates in water, both H+ and Cl- ions are formed, so H+ has a molar concentration.

Andrew Yoon 3L
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Re: Strong Acid and Base

Postby Andrew Yoon 3L » Fri Jan 15, 2021 8:48 pm

H+ or OH- would have molar concentrations because when strong acids/bases react with water, they completely dissociate. H+ can also be written as H3O+. Since H+ and OH- are products in the reaction, they must have a concentration. Dissociation does not mean they disappear.

Shrinidhy Srinivas 3L
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Re: Strong Acid and Base

Postby Shrinidhy Srinivas 3L » Fri Jan 15, 2021 8:51 pm

Hi! So, when you have a strong acid or base, you don't need to make an ICE table because the original molarity of the acid or base will match the molarity of the H+ or OH- (depending on the compound). It's only when you're dealing with weak acids or bases that you need to actually make an ICE table. I hope this helps!


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