Which type of intermolecular force accounts for ea...

Question

Which type of intermolecular force accounts for each of these differences?

(a) Acetone, (CH₃)₂CO, boils at 56°C; dimethyl sulfoxide or DMSO, (CH₃)₂SO, boils at 189°C.

(b) CCl₄ is a liquid at atmospheric pressure and room temperature, whereas CH₄ is a gas under the same conditions.

(c) H₂O boils at 100°C but H₂S boils at -60°C.

(d) 1-propanol boils at 97°C, whereas 2-propanol boils at 82.6°C.

Explain your answers.

Jules Bruno · Accepted Answer

We are being asked to determine the intermolecular force accounting for each of the following differences.(a) Acetone, (CH3)2CO, boils at 56°C; dimethyl sulfoxide or DMSO, (CH3)2SO, boils at 189°C. (b) CCl4 is a liquid at atmospheric pressure and room temperature, whereas CH4 is a gas under the same conditions. (c) H2O boils at 100°C but H2S boils at -60°C. (d) 1-propanol boils at 97°C, whereas 2-propanol boils at 82.6°C. Intermolecular Forces (IMF) are the attractive forces between 2 molecules.• Ion-dipole▪strongest IMF▪ deals with the attraction between an ion and a polar compound.• Hydrogen Bonding[readmore]▪2nd strongest IMF▪ exists anytime hydrogen is directly connected to fluorine, oxygen or nitrogen• Dipole-Dipole▪3rd strongest IMF▪ exists when two polar covalent compounds interact•Dipole/Induced Dipole▪4th strongest IMF▪ deals with the attraction between a polar and nonpolar covalent compound •London-Dispersion Forces/Van der Waals Force/Induced Dipole-Induced Dipole▪weakest IMF▪ intermolecular force is found in all compounds, but it's the main intermolecular force of nonpolar covalent compounds(a) Acetone, (CH3)2CO, boils at 56°C; dimethyl sulfoxide or DMSO, (CH3)2SO, boils at 189°C. • Acetone, (CH3)2CO ▪ presence of the electronegative oxygen (O)→ there will be a net dipole moment in the direction of oxygen▪ acetone →polar covalent compounds →dipole-dipole interaction• DMSO, (CH3)2SO▪presence of the electronegative oxygen (O)→ there will be a net dipole moment in the direction of oxygen▪ DMSO →polar covalent compounds →dipole-dipole interactionThe difference between the two compounds is the greater electronegativity of the S=O bond in DMSO compared to the C=O bond in acetone. This is why DMSO has a higher boiling point.Answer: The intermolecular force that accounts for the difference is the greater dipole-dipole interaction in DMSO than in acetone(b) CCl4 is a liquid at atmospheric pressure and room temperature, whereas CH4 is a gas under the same conditions. • CCl4▪ composed of nonmetal (C) and nonmetal (Cl) →covalent compound▪ C (the less electronegative element) will be surrounded by the four chlorines (Cl) producing a polar C-Cl bond▪ C is surrounded by the same element →nonpolar▪ can only exhibit London-Dispersion Forces• CH4▪ made up of C and H only → hydrocarbon▪hydrocarbons are nonpolar▪can only exhibit London-Dispersion ForcesThe difference between the two compounds is the polar bond in CCl4 that is absent in CH4. This is why CCl4 has greater forces that hold it together making it liquid at room temperature.Answer: The intermolecular force that accounts for the difference is the greater London-Dispersion forces in CCl4 due to its polar bonds compared to CH4 that does not have polar bonds.(c) H2O boils at 100°C but H2S boils at -60°C. • H2O▪ water has an electronegative atom (O) → there will be a net dipole moment in the direction of oxygen▪ H2O →polar covalent compounds →dipole-dipole interaction• H2S▪ presence of the electronegative oxygen (O)→ there will be a net dipole moment in the direction of sulfur▪ H2S →polar covalent compounds →dipole-dipole interactionThe difference between the two compounds is the presence of hydrogen bonding in H2O that is absent in H2S. This is why H2O has a greater intermolecular force and a greater boiling point than H2S.Answer: The intermolecular force that accounts for the difference is the greater dipole-dipole interaction in H2O than in H2S(d) 1-propanol boils at 97°C, whereas 2-propanol boils at 82.6°C. •1-propanol▪ has an H is attached to O that can participate in H-bonding▪ but is mainly composed of C and H → hydrocarbon → London dispersion▪ exhibit both H-bonding and London dispersion•2-propanol▪ has an H is attached to O that can participate in H-bonding▪ but is mainly composed of C and H → hydrocarbon → London dispersion▪ exhibit both H-bonding and London dispersionThe difference between the two compounds is the branching of 2-propanol. Since 2-propanol is more branched than 1-propanol, it will have a lower surface area for London-dispersion making it easier to boil. So, 2-propanol will have a lower London dispersion force compared to 1-propanolAnswer: The intermolecular force that accounts for the difference is the greater London-dispersion in 1-propanol than in 2-propanol

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