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Offlinepeace_n_love
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Chem Help !? * 1
    #8104534 - 03/05/08 01:53 AM (16 years, 2 months ago)

Hey, so I don't know if this is the right forum, but I've got a couple questions about chemistry and thought someone here might know the answers. I've been sick for the last week so these questions aren't making any sense to me. Here they are.

1)2H2O + energy <-> H3O+ + OH-

Is there an increase or decrease in the concentration of H3O+? OH-? Is there an increase, decrease or no change in the Kw.

2)Calculate the Kb of CH3NH2 in a 0.0200M flask with a pH of 11.40.

3)In 0.10M H2SO4, list the ions in decreasing concentration:
H30+ , HSO4-, SO4 2-, OH-

4)Which factors does the strength of an acid depend on?
Energy, pH, concentration, degree of ionization?


anyways, if someone knows the answers, I would be very appreciative.

Peace :mushroom2:

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Invisiblejohnm214
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Re: Chem Help !? [Re: peace_n_love]
    #8104680 - 03/05/08 03:19 AM (16 years, 2 months ago)

4) is a stupid question. I don't know what the fuck they want.


3) you've got a diprotic acid, so more H3O+, then HSO4-, then SO4- then OH-

so acid is the most cuz its an acid, der, then the conjugate base of the first deprotonation, then the conjugate base of second deprotonation, then OH- will be smalles cuz your dealing w/ an acidic solution here

2.pOH= 14-pH; and then the opposite of the usual henderson hasselbach formula gives you


the BH+ is the {CH3NH3+] which equals the amount of [-OH] in solution (calculate from pH or pOH) and B = CH3NH2 which equals initial concentration of base- [OH-] concentration


so your equation is like pOH=pKb +log10 {[OH-]/[.020 - [OH-]]}

then solve for pKb and pKb equals negative log of Kb, and solve for Kb, and hopefully close to the real value of 5x10^-4

1. is written poorly, presuming the energy is to be added to the system (in which case it should have been over or under the equilibrium arrows) what they want is for you to say that H30 and OH increase along with Kw

This is because Kw is only constant for a given temp, and it increases proportionally with the temp of water. So the pH goes down as you heat water... and so does the pOH, crazy...


Hope that helped somewhat.. double check my stuff, I'm tired and take no responsibility

p.s. there is a chemistry board here

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