TABLE 5: Aicohols Molecule Lewis Structure Molar Miscible or Polar or Physical m
ID: 1080852 • Letter: T
Question
TABLE 5: Aicohols Molecule Lewis Structure Molar Miscible or Polar or Physical mass Immiscible non Properties 60.1 1-propanol C,H,o CH,CH,CH,OH Boiling Pt. 97.4°C Density 0.803 g/mL 741 73 g/L 1-butanol C,H, 0 CH (CH,),CH,OH Boiling Pt. Density 0.810 g/mL 1-pentanol C, H120 CH,(CH,),CH,OH 88.2 22 g/L Boiling Pt. 137°C Density 0.811 g/mL 1-hexanol C,HO CH (CH,),CH,0H 102.2 5.9 g/L Boiling Pt. 158 Density 0.814 g/mlL 1 - decano1 158.3 3.7 g/L Boiling Pt. 233°C CH (CH,),CH,OH Density 0.830 g/ml 1. What Intermolecular forces exist in these compounds? 2. How does the solubility change with molar mass? Explain why we see this trend. 3. Is the trend you see in the boiling point and density as the molar mass of the above compounds increase the same as the hydrocarbons and ketones? 4. Find a hydrocarbon (an alkane), a ketone, and an alcohol with roughly the same MW (within 5 g/mole). Rank these compounds in terms of relative boiling points from lowest to highest. What is the factor that causes the differences in the boiling points?Explanation / Answer
1. Hydrogen bonding interaction
Explanation: Hydrogen bond exists between the electronegative atoms (N, O, F) and hydrogen (H).
Here, the electronegative atom is oxygen, i.e. O-H....O
2. The solubility increases with increase in molar mass in the given case.
i.e. 1-propanol < 1-butanol < 1-pentanol < 1-hexanol < 1-decanol
Explanation: As the chain length (i.e. molar mass) increases, the density increases, i.e. the solubility increases.
3. Yes, the trend in the boiling point and density as the molar mass of the given compounds increase the same as the hydrocarbons and the ketones.
Examples of hydrocarbons:
Pentane, CH3(CH2)3CH3: Molar mass = 72.2 g/mol, boiling point = 36.1 oC and density = 0.626 g/mL
Hexane, CH3(CH2)4CH3: Molar mass = 86.2 g/mol, boiling point = 68 oC and density = 0.655 g/mL
Examples of ketones:
Propanone, CH3COCH3: Molar mass = 58.1 g/mol, boiling point = 56 oC and density = 0.784 g/mL
Butanone, CH3COCH2CH3: Molar mass = 72.1 g/mol, boiling point = 79.64 oC and density = 0.805 g/mL
4. Hydrocarbon = pentane
Ketone = butanone
Alcohol = 1-butanol
The boiling point form lowest to highest: pentane (1) < butanone (2) < 1-butanol (3)
Explanation: In hydrocarbons like pentane, only dispersion forces (LDF) exist.
In ketones like butanone, dipole-dipole interactions exist
In alcohols like 1-butanol, both the dipole-dipole interactions and the hydrogen bonding interactions exist.
The strength of Van der Waal's force: LDF < dipole-dipole < hydrogen bonding
As the strength of Van der Waal's forces in the molecule increases, the boiling point increases.
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