Question

28 Report Sheet Identification of Substances by Physical Properties 8. When water and bromoform are mixed, two layers form. Is the bottom layer water or bromoform? (See Table 2.1.) 9. What solvent would you use to determine the density of zine chloride? The density of a solid with a melting point of 429 to 44°C was determined to be 0.87 40.02 g/mL. What The density of a solid with a melting point of 420 to 44°C was determined to is the solid? 10. be 0.87 ±0.02 g/mL, what I. The density of a liquid whose boiling point is 55° to 57°C was determined to be 0.77±0.05 g/mL. what is the liquid? Which has the greater volume-10 g of hexane or 10 g of toluene? What is the volume of each?

Answer 1

Hi, the answers are here:

1. Density, volume, mass, melting point, boiling point

2. $density = \frac{mass}{volume} = \frac{1.22 g}{1.73 cm^{3}} = 0.705 g/cm^{3}$

3. You should see that table 2.1. However, please note that substance whose melting points are above room temperature, are solids while others are liquids or gases. From my own knowlegde, I can tell you that these two substances are solids at room temperature.

4. If cannot determine the density of a solid if it is soluble in a solvent. You can weight a sample of zinc chloride and have its volume determined by displacement in a solvent where it does not dissolve. Since, zinc chloride is soluble in water, you cannot determine its volume and hence density determination is not possible.

5. Are you given any table for this? since I believe this question is a bit difficult if you use real formula. Technically I would do it using the Clausius-Clapeyron equation but, I would suggest you use some table. However, the boiling point that I calculated is 64 degrees.

6. Calibration of thermometers and pipets is necessary since the volume that we measure using a pipet depends upon temperature as glass expands at higher temperatures. So, the volume delivered by a pipet is variable under different temperature values. Therefore calibration of pipets at a certain temperature is necessary. This is also true for thermometers since their data needs to be authenticated.

7. Again you need the table. However, toluene is non-polar and is not miscible with water but it is miscible with ethanol.

8. The liquid which has a higher density will be at the bottom. Bromoform will be at the bottom, since it is denser than water.

9. You should use a solvent where zinc chloride is not soluble. Zinc chloride will not dissolve in bromoform or toluene.

10. You should see the table 2.1 for this. However, I would geuss that it is lauric acid since its melting point is 43.2

11. It could be acetone since it fits into the given data.

12. Remember density and volume have an inverse proportion among them. So, you have 10 g each of hexane and toluene and since toluene is denser than hexane, it will have smaller volume. So hexane is your answer, since it will have greater volume owing to its smaller density.