Question about conductivity?

Question

1) What must we know about a given ionic salt to be able to predict whether it is a good or poor conductor, without testing its conductivity?

2) When doing a conductivity test, what controls the brightness of the light? Is it tap water or NaCl?

Answer 1

NaCl is an ionic compound; Na+ and Cl-.
When it dissolves in water, it forms an eletric current, Na+ ions attracts negative electrodes, and the Cl- ions attracts the positive electrodes. Dissolving NaCl in water increases the glow of the light bulb, since pure water is is a weak electrolyte, it does not serve as a good conductor of electricity.

Answer 2

For part 1) you need to know the dissociation constant (ionization constant). Salts with high dissociation constants will be better conductors (in solution) than salts with low dissociation constants.