Dissolved minerals trapped in magma under tremendous pressure provide the force for a volcanic eruption.

The given statement is false.  

As it is the dissolved gases, not the dissolved minerals, which are trapped in magma under tremendous pressure that provide the force for a volcanic eruption. The magma comprises dissolved gases that offers the driving force, which makes the majority of volcanic eruptions.  

As magma reaches towards the surface and the pressure reduces, the gases get discharged from the liquid part of the magma and continue to move upward and finally get discharged into the atmosphere.  

law of conservation of matter

the electrical  conductivity  of asolution  of an electrolyte is measured by determining the resistance of thesolution  between two flat or cylindrical electrodes separated by a fixed distance.