help! i dont understand this simple chemistry stuff...

[percywilkins]

I dont understand why NaNO2 is considered basic because "NO2- is hydrolyzed with the formation of OH- ions". Where do NO2- and OH- even come from? Do you write the reaction like NaNO2 + H20 ---> and do something from there? I really don't understand this stuff...but the rest of the stuff im good on.

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[percywilkins]

NO2 comes from HNO2 whihc is a weak acid. I belive that was one of the questions from AAMC9. AAMC 9 I thought was pretty tough... i don't know how I got 13 for PS but my BIo went down to 11 and I still think it was hard...

so you just have to pretend NaNo2 is just HNO2?

 

[estairella]

I dont understand why NaNO2 is considered basic because "NO2- is hydrolyzed with the formation of OH- ions". Where do NO2- and OH- even come from? Do you write the reaction like NaNO2 + H20 ---> and do something from there? I really don't understand this stuff...but the rest of the stuff im good on.

NaNO2 is composed of Na+ and NO2-

strong base: NaOH -> Na+ and OH-
by definition of a strong base, the reverse reaction does not occur, therefore Na+ is neutral

weak acid: HNO2 -> H+ and NO2-
by definition of a weaki acid, the reverse reaction does occur, therefore NO2- is a weak base (base neutralizes acid, the H+ ion)

Na+ is neutral, NO2- is basic, overall, NaNO2 is basic

 

[percywilkins]

but how does OH- and NO2- exist in the same solution? Doesn't NO2- on the reactant side proceed to grab an H from H20, so the products end up as HNO2 and OH-?

maybe its the wording of the answer that is messing me up.

 

[estairella]

but how does OH- and NO2- exist in the same solution? Doesn't NO2- on the reactant side proceed to grab an H from H20, so the products end up as HNO2 and OH-?

maybe its the wording of the answer that is messing me up.

That's exactly what happens, the characteristic behaviour of a base.

 

[quadmanturbo]

NaNo2 is a salt..........No2- is an electron donating group so if u add that to a ring it'll also become basic..........by the way, I think u need to brush up on the definitions of acids and bases..........Arrhenius'.........Bronsted-Lowry's and Lewis'.......which usually appear repeatedly on the MCAT....I think lol

 

[sj786]

I think the OH- in the answer was confusing. I got the part that it was a weak base because it was the conjugate base of the acid

 

[gdawg102]

I had hard time understanding what they meant by "hydrolyzed" as well. I took it as perhaps meaning "NO2- after it dissociates with Na+, reacts with H20 and it's H proton, to produce some -OH ions and HNO2 molecules"....HNO2 is a weak acid, which means that its tendency to let go of the H proton is very weak..it does not want to let go of H as does a strong acid such as HNO3.

HNO2 --> H+ + NO2-(conjugate base---according to Princeton review's book, a weak acid has a conjugate base that is a "base"...vs. a strong acid which has a conjugate base that does not react with water (doesn't have an urge to have a hydrogen proton on it as NO2- does) since it's stable on its own with the negative charge on it.

I hope this helped....

~grace

 

[Foolins]

exactly....HNO2 is a weak acid. So it has a conjugate base that's stronger than its conjugate acid.

Therefore, the salt is JUST the conjugate base (NO2-)

So it reacts with H20 to abstract a proton....if you take a proton from H20, you get OH-. So that's where the OH comes from.....it comes from water.