Member of the Month

KilaTsunami
October, 2024

Online

Welcome to the Newschoolers forums! You may read the forums as a guest, however you must be a registered member to post. Register to become a member today!

AP CHEM +k

profile picture
EVAN.F
Posts: 895 - Karma: 2,820
help would be much appreciated. +k

Calculate the OH- ion concentration and pH of the following solution: .080M Na2CO3
Mar 17 2009 10:08PM
0 0
profile picture
dwhite
Posts: 1499 - Karma: 32
i too am having trouble on like the same thing....i dont really know whats going on
Mar 17 2009 10:12PM
0 0
profile picture
robtheslobonacob
Posts: 471 - Karma: 17
is that the whole question or is there some more info about volume and whatnot?
Mar 17 2009 10:15PM
0 0
profile picture
Slinger1x1
Posts: 8853 - Karma: 66
im in normal chem, but im going into AP next year

i feel like your leaving something out
Mar 17 2009 10:18PM
0 0
profile picture
EVAN.F
Posts: 895 - Karma: 2,820
oh right, Ka value for H2CO3 is 4.3 x 10^-7, Ka2 is 5.6 x 10-11 (except im not sure you need this)

I'm not sure if the balanced equation is

(CO3)2- + 2(H20) = H2CO3 + 2(OH-)

or

(CO3)2- + (H20) = HCO3-  + (OH-)

but you use an ICE table, im pretty sure on that
Mar 17 2009 10:27PM
0 0
profile picture
chapz
Posts: 10182 - Karma: 66
^ yeahh, have you dont buffers or whatever? or are you just doing pOH and -log[OH]? or have you done Ka and Kb and stuff like that>
Mar 17 2009 10:32PM
0 0
profile picture
EVAN.F
Posts: 895 - Karma: 2,820
^no not really buffers, mainly just the Ka and Kb and pOH.
Mar 17 2009 10:43PM
0 0
profile picture
spqr
Posts: 182 - Karma: 141
all I know is that your pOH is the opisite of the log of the OH concentration... that I had beat into my head in highschool.
Mar 17 2009 11:19PM
0 0
profile picture
freezed
Posts: 12973 - Karma: 500
find the OH- concentration using your ICE table, then 14 - (-log[OH-]) = pH.
Mar 17 2009 11:25PM
0 0
profile picture
EVAN.F
Posts: 895 - Karma: 2,820
ok, to set up my ICE table would I use

(CO3)2- + 2(H20) = H2CO3 + 2(OH-)

or do 2 ice tables

(CO3)2- + (H20) = HCO3-  + (OH-)

HCO3- + (H20) = H2CO3 + OH-

Ka1 = 4.3 x 10-7 Ka2 = 5.6 x 10^-11

I'm beginning to think which BE to use can only be answered by my teacher who wrote the question...


Mar 17 2009 11:38PM
0 0
profile picture
An10a_Eng
Posts: 2505 - Karma: 26
Henderson Hasselbach equation
Mar 18 2009 12:25AM
0 0
All times are Eastern (-5)