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I am doing a lab on carbon dioxide solubility in water and I have a non-linear trend which seems to agree with the accepted trend. I am examining the change in solubility as a function of temperature. In the experiment I titrated carbonated water with sodium hydroxide and used molar ratios to determine the carbon dioxide content. The following graph shows the accepted trend:

Solubility Curve

(Graph from: http://www.rocketscientistsjournal.com/2006/10/co2_acquittal.html)

I've been thinking but, can't seem to figure out why the trend is non-linear. Is there any intuition behind this trend?

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  • $\begingroup$ Nonlinear with respect to what? Amount of water? Amount of CO2? Temperature? Is it a closed system? Please be specific about what you are asking, as well as the experimental setup... $\endgroup$ Mar 6, 2016 at 23:59
  • $\begingroup$ Sorry, it is updated now. $\endgroup$
    – Yulmart
    Mar 7, 2016 at 0:01

1 Answer 1

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The solubility can be thought of as an equilibrium. The Van 't Hoff Equation describes the relationship between any equilibrium constant and temperature.

$lnK_2 - lnK_1 = \frac{\Delta H }{R} (\frac{1}{T_1}-\frac{1}{T_2})$ . Thus, the graph is not linear.

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  • $\begingroup$ I just fixed the equation --there was an extra negative. $\endgroup$
    – Yunfei Ma
    Mar 7, 2016 at 21:32
  • $\begingroup$ Solubility is linearly proportional, however, to pressure. $\endgroup$
    – Yunfei Ma
    Mar 7, 2016 at 21:33

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