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TP The order of normal boiling points is Acetone, CH 3 C O CH 3 30.8 Diethyl ether, CH 3 CH 2 2 O 71.7 Ethanol, CH 3 CH 2 OH 7.87 Water, H 2 O 3.

attraction dispersion ; relative boiling points 1. diethyl ether acetone ethanol 2. ethanol acetone diethyl ether 3. acetone diethyl ether ethanol 4. ethanol diethyl ether acetone 5.

1 TP The order of normal boiling points is Acetone, CH 3 C O CH Diethyl ether, CH 3 CH 2 2 O 71.7 Ethanol, CH 3 CH 2 OH 7.87 Water, H 2 O Lecture 13 CH1 A1 (MWF 9:05 am) Friday, October 6, 2017 For today and boiling Next lecture: Intermolecular forces; hydrogen bonding; dipole dipole interaction polarity ; temporary dipole attraction dispersion ; relative boiling points 1. diethyl ether acetone ethanol 2. ethanol acetone diethyl ether 3. acetone diethyl ether ethanol 4. ethanol diethyl ether acetone 5. something else Response Counter 1 TP From e6.4 p 163 : A bubble in a pot of boiling water contains 1. Only O 2 g and N 2 g 2. Only H 2 O g 3. Only air 4. H 2 O g and air 5. All of the above equally 6. None of the above Liquid-vapor equilibrium 5 6 Copyright 2017 Dan Dill dan@bu.edu 1

2 Boiling: Fig 6.7, p 164 Boiling means bubbles Bubbles are pure vapor of the liquid 7 1 Pa force/area 1 kg m/s 2 / m 2 1 kg m 1 s 2 1 bar 0 kpa exactly 1 atm kpa exactly 8 Low temperature Few particles in vapor Low equilibrium vapor pressure 9 Copyright 2017 Dan Dill dan@bu.edu 2

3 Higher temperature More particles in vapor Higher equilibrium vapor pressure 11 Normal boiling temperature Maximum particles in vapor 1 atm equilibrium vapor pressure 12 and boiling point Can we make bubbles and so boil at a lower temperature? Let s see and boiling Bubbles appear when vapor pressure applied pressure Normal boiling point is when vapor pressure is exactly 1 atm kpa Copyright 2017 Dan Dill dan@bu.edu 3

4 and boiling and boiling Bubbles appear when vapor pressure applied pressure Bubbles appear when vapor pressure applied pressure A vacuum pump allows boiling at lower temperature. A pressure cooker delays boiling to higher temperature and boiling point What do you predict for relative boiling points of these substances? Acetone, CH 3 C O CH Diethyl ether, CH 3 CH 2 2 O 71.7 Ethanol, CH 3 CH 2 OH 7.87 Water, H 2 O TP The order of normal boiling points is Acetone, CH 3 C O CH Diethyl ether, CH 3 CH 2 2 O 71.7 Ethanol, CH 3 CH 2 OH diethyl ether acetone ethanol 2. ethanol acetone diethyl ether 3. acetone diethyl ether ethanol 4. ethanol diethyl ether acetone 5. something else Water, H 2 O Response Counter 20 Copyright 2017 Dan Dill dan@bu.edu 4

and boiling point What do you predict for relative boiling points of these substances? Acetone, CH 3 C O CH 3 3: 30.8 3: 56 Diethyl ether, CH 3 CH 2 2 O 4: 71.

0 Relative normal boiling point, T b What do you predict for relative vapor pressures of these substances at 200 C?

5 and boiling point What do you predict for relative boiling points of these substances? Acetone, CH 3 C O CH 3 3: : 56 Diethyl ether, CH 3 CH 2 2 O 4: : 35 Ethanol, CH 3 CH 2 OH 2: : 78 Water, H 2 O 1: Relative normal boiling point, T b What do you predict for relative vapor pressures of these substances at 200 C? Quiz The substance with the lowest vapor pressure substances at 200 C is Enthalpy change of vaporization, vap H 1. CH 4 2. NH 3 3. HCl 4. N 2 Response Counter 23 H 2 O H 2 O, Δ vap 40.7 kj/mol at 0 C NH 3 NH 3, Δ vap 23.3 kj/mol at 78 C N 2 N 2, Δ vap 5.6 kj/mol at 196 C etc. 24 Copyright 2017 Dan Dill dan@bu.edu 5

6 TP Which of the following is correct about water? 1. The low enthalpy of vaporization results in a low vapor pressure 2. The high enthalpy of vaporization results in a low vapor pressure 3. The low enthalpy of vaporization results in a high vapor pressure 4. The high enthalpy of vaporization results in a high vapor pressure 5. There is no simple relationship between vapor pressure and enthalpy of vaporization 25 Copyright 2017 Dan Dill dan@bu.edu 6

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Copyright 2017 Dan Dill 1 TP An acid has K a 1.0 10 7 at 25 o C. In a c a 0.40 M solution of this acid solution, H 3 O 1. 0.40 2. 0.040 3. 0.0010 4. 0.0020 5. 0.00020 6. 0.00040 7. Something else Lecture 19 CH102 A1 (MWF 9:05 am)