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inutard
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The question below is a rather theoretical one and does not concern any actual calculations. So I have decided to abandon the traditional format.
In the past few weeks, I have designed and carried out a lab in which I would test the resistance of a strong acid (0.5 M HCl), a weak acid (0.5 M vinegar) and water at varying temperatures (10 - 50 deg Celcius to avoid error caused by evaporation). The same volume of solutions put into the same type of beaker (i.e. geometric proportions of the solutions are conserved) with resistance measured across the same two points in the solution every time were used as controls.
I had assumed that the resistances would go down as a function of temperature because:
1) The Keq/dissociation constant of the acid equilibriums increase, thus producing more H3O+ ions and conjugate base ions.
2) The increased temperature increases the kinetic energy of the solutions and the ions therein, thus increasing conductivity and decreasing resistance.
3) Water tends to auto-ionize more at greater temperatures (this relates to point 1 and is also shown to be true in the experiment as the trials show lower resistances versus higher temperatures)
The lab turned out to be a success and a general trend of high temperature / lower resistance was shown. At the onset, this trend looks to be a logarithmic one. However, when I plot conductance (1/R) versus temperature (celcius), the trend becomes linear. In other words, temperature is directly proportional to (1/R).
My question is: Why does this happen?
The lab data is contained in an attachment below.
In the past few weeks, I have designed and carried out a lab in which I would test the resistance of a strong acid (0.5 M HCl), a weak acid (0.5 M vinegar) and water at varying temperatures (10 - 50 deg Celcius to avoid error caused by evaporation). The same volume of solutions put into the same type of beaker (i.e. geometric proportions of the solutions are conserved) with resistance measured across the same two points in the solution every time were used as controls.
I had assumed that the resistances would go down as a function of temperature because:
1) The Keq/dissociation constant of the acid equilibriums increase, thus producing more H3O+ ions and conjugate base ions.
2) The increased temperature increases the kinetic energy of the solutions and the ions therein, thus increasing conductivity and decreasing resistance.
3) Water tends to auto-ionize more at greater temperatures (this relates to point 1 and is also shown to be true in the experiment as the trials show lower resistances versus higher temperatures)
The lab turned out to be a success and a general trend of high temperature / lower resistance was shown. At the onset, this trend looks to be a logarithmic one. However, when I plot conductance (1/R) versus temperature (celcius), the trend becomes linear. In other words, temperature is directly proportional to (1/R).
My question is: Why does this happen?
The lab data is contained in an attachment below.
