Physical Chemistry 2.pdf - OER@AVU - African Virtual University

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Example 2 African Virtual University The solubility of oxygen gas at 0 °C and 101325 Pa is 48.9 mL per litre. Calculate the molarity of oxygen in a saturated water solution when the oxygen is under its normal pressure in air of 0.2095 atm. Solutions The problem is solved by first determining the molarity of the saturated solution at the given temperature and pressure: 1mol O2 0.0489 L x 22. 4 O2 Molarity = = 2.18 x 10 1L According to Henry’s law k = C P gas C = kP gas -3 2.18 x 10 M C = = 1atm 0.2095atm 0.2095M C= x2.18 x10 1atm Practice problem 2 − 3 = 4.57 x10 −4 M -3 M What is the equilibrium concentration (mg O 2 per L) of oxygen gas in fresh water at 25 °C when exposed to air at a pressure of 1 atm? The Henry’s law constant for oxygen in water at 25 °C is 3.0 x 10 7 atm.
Visual demonstration: Forces of cohesion 1.3.3 Liquid in liquid solutions African Virtual University Two liquids are more likely to form a solution if for example for species A and B, the interactions of A-A, B-B and A-B are similar. The intermolecular forces in the two liquids must be similar. For example, the intermolecular forces at play in hexane are mainly dispersion forces (weak forces due to temporary dipoles) and similarly in heptane. Thus, the intermolecular forces that would exist between hexane and heptane are also dispersion forces. These liquids should be miscible. On the other hand if the intermolecular forces are greater in one liquid, for hexane and water, the liquids will not make a solution. Water forms strong hydrogen bonds with other water molecules. Water will tend to be miscible with liquids that can form hydrogen bonds. For example, ethanol and water are completely miscible. NO2+ H2O HNO3 SO2+ H2O H2SO4 ACID RAIN Gas emissions from industries and cars such as sulphur dioxide or nitrogen dissolve in Gas water emissions to form acids, from which industries adversely and cars affects such the as environment. sulphur dioxide or nitrogen dissolve in water to form acids, which adversely affects the environment. 1.3.1 Energy considerations – to mix or not to mix? SO2 NO2 When two liquids mix, there is an increase in entropy in much the same way as when gases mix. Hence the entropy of mixing is always positive. The free energy of mixing therefore for the two liquids may be written as ΔG = ΔH - TΔS (1.2) mix mix mix A negative ΔG favours mixing of the two liquids. For an ideal solution, the enthalpy change is zero and therefore mixing is solely due the positive entropy. However, mixing for some solutions may be either exothermic or endothermic. When mixing is exothermic, it works synergistically with the entropy of mixing to give a more
Page 1 and 2: Physical Chemistry 2 Prepared by On
Page 3 and 4: Table of ConTenTs African Virtual U
Page 5 and 6: IV. Material African Virtual Univer
Page 7 and 8: Unit IV Electrochemistry (20 hours)
Page 9 and 10: Unit Learning objective(s) African
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Page 17 and 18: List of required readings • Solut
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Page 73 and 74: Practice problem 1 What is X in the
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Example 1 African Virtual Universit
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Practice problem 2 African Virtual
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5.7.2 Binding energy and nuclear st
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5.9 Interaction of radiation with m
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(ii) Photoelectric absorption Afric
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African Virtual University Standard
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Reading #3 COLLOIDS African Virtual
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Reading # 9 INTRODUCTION TO RADIOAC
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African Virtual University Rational
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Useful Link #2 Title : Chem1 Virtua
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Useful Link # 5 Title : Chemistry U
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Useful Link # 8 Title : Chemistry R
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Useful Link # 11 Title : RAdiation
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XVI. summative evaluation African V
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(c) 0.09V (d) -0.09V African Virtua
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XVII. References African Virtual Un
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