Marjorie is trying to determine the identity of an unknown substance. After running tests, she determines that the substance is insoluble in CCl4 with a density of about 2.2 g/mL.

Question

Substance Density Boiling Point Solubility (in water) Solubility (in CCl4)
NaCl 2.165 g/mL 1413°C soluble insoluble
C10H8 1.14 g/mL 255°C insoluble soluble
FeCl3 2.898 g/mL 315°C soluble insoluble
SiO2 2.634 g/mL 2590°C insoluble insoluble

Using the data above, which of the following substances is most likely Marjorie's unknown?
A.
C10H8
B.
NaCl
C.
SiO2
D.
FeCl3

Answer 1

To determine which substance is Marjorie's unknown, we need to analyze the provided information regarding solubility and density.

Marjorie's unknown substance has the following characteristics:

• Insoluble in CCl4 (carbon tetrachloride)
• Density of about 2.2 g/mL

Now let's evaluate the options based on these criteria:

A. C10H8

• Density: 1.14 g/mL
• Solubility in CCl4: Soluble
• This does not match since it is soluble in CCl4 and has a density far less than 2.2 g/mL.

B. NaCl

• Density: 2.165 g/mL
• Solubility in CCl4: Insoluble
• This is a strong potential candidate as it matches both the density (close to 2.2 g/mL) and the solubility criteria.

C. SiO2

• Density: 2.634 g/mL
• Solubility in CCl4: Insoluble
• The density is too high compared to 2.2 g/mL, so it does not match.

D. FeCl3

• Density: 2.898 g/mL
• Solubility in CCl4: Insoluble
• This density is also too high compared to 2.2 g/mL.

Based on the analysis, the substance that best matches Marjorie's unknown is B. NaCl.