For example, when reacting Copper (II) Nitrate solution with Sodium Carbonate solution, the conductivity of the solution of Copper (II) Nitrate is seen to fall as more Sodium Carbonate solution is added. Why exactly does this happen?
Ions in solution can transport charge. A precipitation reaction depletes ions from the solution and consequently the conductivity of the solution drops.
Ions in solution can transport charge. A precipitation reaction depletes ions from the solution and consequently the conductivity of the solution drops.
Compounds that dissociate into ionic components can conduct electricity (hence dissolved sugar does not conduct electricity). They are able to flow freely throughout the water, and thereby transport charge. A precipitate is both charge neutral, and not able to move freely in the water. It will eventually settle out of the water.
In the Copper Nitrate and Sodium Carbonate reaction, consider the relation between available ions and the concentration of ions. Copper Nitrate has 2 positive, and 2 negative charges available. After the reaction, there are still 2 positive and 2 negative charges, but some water was added from the Sodium Carbonate solution. This reduces the overall salinity, and therefore reduces the conductivity.
Actual conductance varies from ion to ion. It's essentially how easily it can move through water. Since this example isn't changing the charge carriers to something like a large organic acid, it's not a very significant.
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