Question

At STP, two 5.0-gram solid samples of different ionic compounds have the same density. These solid samples could be dominated by their

Answer 1

Missing question:
1) mass.
2) volume.
3) temperature.
4) solubility in water.
Answer is: 4) solubility in water.
This ionic solids can not be differentiated by mass, because they have same mass (5 g), neither by volume because they have same mass and density, than either and volume (d = m/V), solubility of compound is differente because different ions.