How the law of conservation of mass could be useful for investigating chemical change

If a solution is considered basic, then a) the hydroxide ion and hydronium ion concentrations are equal. b) the hydroxide ion concentration is less than the hydronium ion concentration. c) the hydronium ion concentration is greater than the hydroxide ion concentration. d) the hydroxide ion concentration is greater than the hydronium ion concentration.

The name of the ion, s2-, is: sulfurous ion sulfide ion sulfur ion sulfate ion

Which sample at stp has the same number of atoms as 18 liters of ne at stp