Marjorie's unknown substance is sodium chloride NaCl.
The substance is insoluble in CCl₄. The density of the substance is 2.2 g/mL.
Solubility:
The fact that the chemical is insoluble in CCl₄ (tetrachloromethane), as indicated in the statement, indicates that the substance is polar in nature. Only C₁₀H₈ of the choices is soluble in CCl₄ since they are both non-polar by nature and related substances dissolve similarly. C₁₀H₈ is therefore disregarded.
Density:
There are now only three possibilities left. SiO₂, FeCl₃, and NaCl. The student discovered that the material has a density of 2.20 g/ ml. This is quite similar to sodium chloride's density (i.e., 2.165 g/mL). As a result, sodium chloride is most likely the material the student is working with.
Learn more about soluble here:
https://brainly.com/question/24972177
#SPJ9