Solution of NaCl and CO2. Name species and find concentrations of species.

[geostudent]

So, I'm assuming no Sodium Bicarbonate or Carbonate is formed during this process.

I found the concentrations of the species by basic ICE diagram.

Mostly, I need to know how to approach this problem conceptually . I'm assuming the effect of NaCl on the CO2-->H2CO3-->HCO3- --> CO3-- is negligible, but I really don't know. This is for a geochem class, and I have very little chemistry experience, so any explanations or theory would help tremendously.

Homework Statement

Problemset 3.

1. Consider and NaCl solution into which we introduce CO2 by bubbling gas. Recipe: 10-3M NaCl, 10-4M [CO2]T.
(a) What species are present?

(b) What reactions take place?

(c) What is the concentration of the species

(d) Now add 10-4.5M [NaOH]T .What is the alkalinity of the solution?

H2CO3*=H++HCO3-; pK1=6.3 (I)
HCO3-=H++CO32-; pK2=10.3 (II)

Homework Equations

The Attempt at a Solution

(a) What species are present?

Species present are Na+ , Cl-, H+, OH-, HCO3- , CO32- , H2CO3 and CO2 (aq), Na2CO3, NaHCO3


(b) What reactions take place?

(c) What is the concentration of the species


[HCO3-]= 2.07E-5
[H+] ~ 2.07E-5
[CO32-]=5.62E-11

[Na+] = .001 M

[Cl-] = .001 M

[HCO3-]= 2.07E-5

Using this below.


H2CO3 HCO3- + H+ pKa1 (25 °C) = 6.37
HCO3-  CO32- + H+ pKa2 (25 °C) = 10.25


H2CO3 HCO3- + H+ pKa1 (25 °C) = 6.37 Ka1=4.3E-7
HCO3-  CO32- + H+ pKa2 (25 °C) = 10.25 Ka2 =5.62E-11


H2CO3 HCO3- H+
I 1E-3 0 0
C -x +x +x
E .001-x x x

Ka1= [HCO3][H]/[H2CO3] = x2/ .001-x = 4.3E-7

[H+]=[HCO3-]=2.07E-5


The second dissociation contributes very little [H+] =5.62E-11


[H+] ~ 2.07E-5

[CO32-]=5.62E-11

 

[Borek]

NaCl presence changes ionic strength of the solution, so it slightly changes equilibrium concentrations of all ions present in the solution. Not enough to make it a problem.

x2/ .001-x = 4.3E-7

.001 or .0001?

 

[geostudent]

.0001. Sorry.