States Of Matter Gases And Liquids L-3
States of matter
States Of Matter Gases And Liquids L-3
Intermolecular forces
- Ion - ion interaction
- Ion - dipole interaction
- Dipole - dipole interaction
- Dipole - induced dipole
- Induced dipole - induced dipole
States Of Matter Gases And Liquids L-3
Intermolecular forces
- Functional form
- Strength of various intermolecular forces
- Dependence on Various properties
States Of Matter Gases And Liquids L-3
Problem
Problem - Which of the following molecule have a dipole - dipole interaction ?
(a) CO2
(b) CH2Cl2
(C) CH4
Ans
Structure of the molecule
Qualitative idea about the electronegative of elements
Vectorial additon
Molecule that have a dipole - dipole interaction is
(b) CH2Cl2
States Of Matter Gases And Liquids L-3
Problem
- Problem - predict the relative boiling point of CH3COOH and CH3OH
- Boiling point of acetic acid is higher than methanol
States Of Matter Gases And Liquids L-3
Dipole - induced dipole interaction
Water - life (fishes)
O2 and N2 is dissolved in water
O=O is non polar and has no dipole
O=O→ induced dipole
States Of Matter Gases And Liquids L-3
Polarizability
- α measures the size of the induced dipole
- μind =αE
- Larger the α , larger is the induced dipole
| Polarizability/10−25cm3 | Molar mass/amu | Boiling point/K | |
|---|---|---|---|
| H2 | 7.9 | 2 | 20k |
| O2 | 16 | 32 | 90k |
| N2 | 17.6 | 28 | 77k |
| CH4 | 26 | 16 | 109k |
States Of Matter Gases And Liquids L-3
Polarizability
- CH4−C2H6−C3H8−C4H10
- α increases
- Boiling point increases
| Polarizability/10−25cm3 | Molar mass/amu | Boiling point/K | |
|---|---|---|---|
| C2H6 | 44.7 | 30 | 185k |
| C3H6 | 62.9 | 44 | 231k |
| CCl4 | 105 | 154 | 350k |
| Cl2 | 246 | 71 | 238k |
States Of Matter Gases And Liquids L-3
Polarizability and london dispersion force
- Fritz london
- H3C - CH2-CH2-CH3
- n - Butane has higher boiling point
- Straight chain (larger the molecule) more polarizable - higher boiling point
- Then , dipole - induced dipole interactions are higher
States Of Matter Gases And Liquids L-3
Interaction in molecule
- Dipole - induced dipole
- Liquid O2
- O=O no permanent dipole moment
- Electron density is symmetric at equilibrium
- Instantaneous dipole - asymmetric electron density
- All molecules show dispersion forces
States Of Matter Gases And Liquids L-3
Problem
- Problem - The bp of propane , n− butane , n−pentane , and n− hexane are respectively , [−42.1oc,0.5oc,36.1oc and 68.7oc] explain this trend
| Molecule | Molecule mass | BP |
|---|---|---|
| CH3 CH2 CH3 | 44 | ↓ |
| n−C4 H10 | 58 | ↓ |
| n−C5 H12 | 72 | ↓ |
| n−C6 H14 | 86 | ↓ |
Ans
London - dispersion forces
Dipole - induced dipole
Induced dipole - induced dipole
States Of Matter Gases And Liquids L-3
London dispersion forces
- V(r)∝r61
- Similar to dipole - dipole
States Of Matter Gases And Liquids L-3
Interaction in molecules
States Of Matter Gases And Liquids L-3
Problem
- Problem - Identify intermolecular interaction present in CH3CH3,CH3OH,CH3CH2OH
- What do we know - Structure of the molecules functional groups (polar) , molar mass
- Strategy - Determine the type of interaction in each molecule follow the chart
States Of Matter Gases And Liquids L-3
Problem
- Problem - Rank the following in order of increasing strength of intermolecular forces in the pure substance
- (a) CH3CH2CH2CH3
- (b) CH3CH2OH
- (C) He
- Solution
- What do we know? Structure , functional groups
- Strategy ? Flow chart & know the relative sizes of various intermolecular interaction
States Of Matter Gases And Liquids L-3
Problem
- Problem - Which of the following compound is expected to form intermolecular hydrogen bonds in the legend state ?
- (a) CH3 OCH3
- (b) CH4
- (c) HF
- (d) CH3COOH
- (e) Br2
- (f) CH3Or+
States Of Matter Gases And Liquids L-3
Problem
- Problem - In each spare of ionic compounds. which is more likely to have the more negative enthalpy of, hydration ? Briefly explain your reasoning
- (a) LiCl or CsCl
- (b) NaNO3orMg(NO3)2
- (c) RbClorNiCl2
States Of Matter Gases And Liquids L-3
Problem
- Problem - Amongest H2NNH2,H2C=CH2 , CH3CH2CH2CH3 , predict which would have -
- (a) the longest dipole-dipole forces and (b) the lowest boiling point
States Of Matter Gases And Liquids L-3
Intermolecular Interaction
- Ion - ion highest
- Hydrogen bond
- Ion - dipole
- Dipole - dipole
- Dipole - induced dipole
- Induced - induced dipole
States Of Matter Gases And Liquids L-3
Properties of gases
- Empty spaces
- Random positions
- Constant motion
- Intermolecular interactions small
States Of Matter Gases And Liquids L-3
Why study gases ?
- Fundamental - interaction small between molecules limiting case - no interaction
- Life depends on atmosphere (gas)
- Recent practical instant (reaction in the gase phase in the environment)
- Classic experiments (atomism/ Avogadro's)
States Of Matter Gases And Liquids L-3
Gases
- Ideal gas (no intermolecular system)
- Real gas (van der waals)
- Boyle's law
- Charles & gay - Lussac's law
- Avogadro's hypothesis
- Ideal gas equation of state
States Of Matter Gases And Liquids L-3
Thank you
States Of Matter Gases And Liquids L-3 States of matter $\rightarrow$ $\rightarrow$ States of matter $\rightarrow$ Intermolecular forces $\rightarrow$ Intermolecular forces