Which of the following apply to concentration?

Concentration of products can vary.

As more solute dissolves, more ions form; but the volume in which they are contained does not change.

Concentration of the solid phase does not change.

Explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)