I know that impure water(containing salts) or acidified water can conduct electricity but pure water is a poor conductor of electricity. So is it possible? Please explain.

  • $\begingroup$ To make pure water more conductive, you could add salt or other impurities. What kind of answer did you have in mind? $\endgroup$ – The Photon Jun 5 '17 at 15:55
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    $\begingroup$ Photon.......I wanted a answer like Floris gave. I wanted to know of any possibilities to make pure water better conductor, keeping its purity i.e. by NOT adding impurities. $\endgroup$ – Che Jun 5 '17 at 16:03

Conductivity in water is due to the presence of ions.

Pure water has few ions at room temperature: the dissociation constant is about $10^{-14}$ at room temperature, increasing almost 50x as you reach the boiling point reference. Higher dissociation = better conductivity.

So it's possible to increase the conductivity of pure water significantly by heating it.

I found a graph of this relationship in the Suez water treatment handbook that shows roughly a 20x increase in conductivity between 20°C and 100°C . Now the since the dissociation constant is the product of $\rm[OH^-]$ and $\rm[H_3O^+]$ concentrations, while the conductivity depends on the total number of ions and their mobility, you would expect conductivity to scale roughly with the square root of the dissociation constant; but there will be an added factor due to ion mobility (which will increase with temperature). So ~20x increase in conductivity is a reasonable value.

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  • $\begingroup$ Conductivity in solutions also depends on electrical mobility; it's not clear to me how this would vary with temperature, though I wouldn't be surprised if it increases as well. $\endgroup$ – Michael Seifert Jun 5 '17 at 16:05
  • $\begingroup$ @MichaelSeifert - good point. See update. $\endgroup$ – Floris Jun 5 '17 at 16:15

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