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Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
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tonichilds83 tonichilds83
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Posts: 64
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12 years ago
What is the concentration of undissociated acid if it hydrogen-ion concentration is 0.0001 M and the acid dissociation constant is 0.0000001?

a) 1 x 10^-1 M
b) 1 M
c) 1 x 10^-4 M
d) 10 M
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wrote...
#1
12 years ago
[HA]=[H+][A-]/Ka
[H+]=[A-]
[HA]=[H+]^2/Ka
[HA]=(10^-3)^2/10^-6= 1M
wrote...
#2
12 years ago
when the acid dissociates
HA  Rightwards Arrow H+    +    A-

initially [HA] = x mol/L
           [H+] = 0
           [A-] = 0

after dissociation [HA] = x - 0.0001  mol/L
           [H+] = 0.0001 mol/L
           [A-] = 0.0001 mol/L

now you are able tho determine the value of x and thus the concentration of the undisociated acid which is  (x-0.0001) since the concentrations of HA ,H+, and A- are related by the acid dissociation constant given to be 10^-7

[HA] = 10^-1 mol/L
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