Question

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.

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.
SiO2
B.
C10H8
C.
NaCl
D.
FeCl3

Answer 1

To determine which substance is most likely to be Marjorie's unknown, we can analyze the provided information:

1. The unknown substance has a density of about 2.2 g/mL.
2. It is insoluble in CCl4.
3. Its boiling point has not been specified but may be inferred from the provided data.

Now, let's examine the options:

A. **SiO2**
- Density: 2.634 g/mL
- Boiling Point: 2590°C
- Solubility in CCl4: Insoluble
- Conclusion: The density is slightly higher than 2.2 g/mL.

B. **C10H8**
- Density: 1.14 g/mL
- Boiling Point: 255°C
- Solubility in CCl4: Soluble
- Conclusion: Does not match due to solubility and density.

C. **NaCl**
- Density: 2.165 g/mL
- Boiling Point: 1413°C
- Solubility in CCl4: Insoluble
- Conclusion: The density is close to 2.2 g/mL and it is insoluble in CCl4, but also soluble in water.

D. **FeCl3**
- Density: 2.898 g/mL
- Boiling Point: 315°C
- Solubility in CCl4: Insoluble
- Conclusion: The density is higher than 2.2 g/mL.

Based on these comparisons, **NaCl** (Option C) is the best match despite being soluble in water, which is a common property of many salts.

**Final Answer**: C. NaCl