Chemistry on Freezing and Boiling Points
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Questions and Answers

What type of force do the gases in the table only exhibit?

  • Dispersion force (correct)
  • Ionic bond
  • Covalent force
  • Hydrogen bonding

    • What describes the miscibility of hexane and water?

  • They dissolve completely.
  • They are both polar.
  • They are miscible.
  • They are immiscible. (correct)

    • Which type of vitamin needs to be included in the daily diet due to its solubility?

  • Water-soluble vitamins (correct)
  • All vitamins
  • Fat-soluble vitamins
  • Nonpolar vitamins

    • How does pressure affect the solubility of gases compared to solids and liquids?

    <p>Gases are affected by pressure.</p> Signup and view all the answers

    According to Henry's Law, what occurs if the partial pressure of a gas over a liquid is doubled?

    <p>There are twice as many gas molecules in the liquid.</p> Signup and view all the answers

    What property of liquid mixtures is defined as 'immiscible'?

    <p>They do not mix at all.</p> Signup and view all the answers

    What type of organic molecules dissolve in water better?

    <p>Polar organic molecules</p> Signup and view all the answers

    Which gas property is proportional to the Henry's law constant at a constant temperature?

    <p>Solubility of the gas</p> Signup and view all the answers

    What is the formula used to calculate the change in freezing point (∆Tf)?

    <p>∆Tf = iKf*m</p> Signup and view all the answers

    How do you calculate the boiling point elevation (∆Tb)?

    <p>∆Tb = iKb*m</p> Signup and view all the answers

    What value of Kf is used in the calculations provided?

    <p>1.86 °C/m</p> Signup and view all the answers

    What is the molality of the solution calculated in the content?

    <p>5.37 m</p> Signup and view all the answers

    What is the freezing point depression calculated in the content?

    <p>-10.0 °C</p> Signup and view all the answers

    What is the final boiling point of the solution as calculated?

    <p>102.7 °C</p> Signup and view all the answers

    What is the value of Kb used for determining the boiling point elevation?

    <p>0.51 °C/m</p> Signup and view all the answers

    Which variable represents the van 't Hoff factor in the freezing and boiling point calculations?

    <p>i</p> Signup and view all the answers

    What is the calculated molarity of the solute in the solution?

    <p>0.0711 M</p> Signup and view all the answers

    What is the van’t Hoff factor (i) for sodium chloride (NaCl) upon dissociation?

    <p>2</p> Signup and view all the answers

    What is the mass in grams of the solute used in the calculation?

    <p>88 g</p> Signup and view all the answers

    Which of the following correctly describes the relationship between solute concentration and the van’t Hoff factor?

    <p>The van’t Hoff factor can vary based on concentration.</p> Signup and view all the answers

    What does the equation $m = (0.0711 ext{ mol/kg soln}) * (40.0 imes 10^{-3} ext{ kg soln})$ calculate?

    <p>The number of moles of solute.</p> Signup and view all the answers

    What is the formula used to obtain the molar mass of the solute?

    <p>Molar mass = mass/moles</p> Signup and view all the answers

    What physical property does a van’t Hoff factor of 1 suggest about a solute?

    <p>It does not dissociate in solution.</p> Signup and view all the answers

    In the calculation method for finding the number of moles of solute, which unit conversion is necessary?

    <p>From kg to g</p> Signup and view all the answers

    What is the composition of the toluene:benzene mixture before boiling?

    <p>70:30</p> Signup and view all the answers

    What enriched fraction of benzene can be obtained after the first step of distillation?

    <p>50%</p> Signup and view all the answers

    What happens when an azeotropic solution is reached?

    <p>Components cannot be separated further by distillation.</p> Signup and view all the answers

    Which of the following describes osmosis?

    <p>Movement of solvent from low to high concentration.</p> Signup and view all the answers

    What is the osmotic pressure of blood at 25 °C?

    <p>7.7 atm</p> Signup and view all the answers

    What type of membrane allows certain smaller particles to pass while blocking larger ones?

    <p>Selectively permeable membrane</p> Signup and view all the answers

    What is the van’t Hoff Factor represented as in the equation for osmotic pressure?

    <p>i</p> Signup and view all the answers

    What is the molar mass of glucose (C6H12O6)?

    <p>180 g/mol</p> Signup and view all the answers

    What is the definition of an isotonic solution?

    <p>It has the same osmotic pressure; solvent passes the membrane at the same rate both ways.</p> Signup and view all the answers

    What occurs to red blood cells in a hypertonic solution?

    <p>They shrivel as water leaves the cell.</p> Signup and view all the answers

    Which statement is true regarding a hypotonic solution?

    <p>It results in water entering the cell more than it leaves.</p> Signup and view all the answers

    What happens during hemolysis?

    <p>Cells swell and eventually burst due to water influx.</p> Signup and view all the answers

    Which of the following accurately describes osmotic pressure?

    <p>It is the pressure that results from differences in solute concentrations across a membrane.</p> Signup and view all the answers

    What is the primary consequence of storing red blood cells in a hypotonic solution?

    <p>They will hemolyze as water enters.</p> Signup and view all the answers

    What characteristic distinguishes a hypertonic solution?

    <p>It has a higher osmotic pressure than the interior of a cell.</p> Signup and view all the answers

    In the context of molality and the provided data, what is the molarity (M) calculated?

    <p>0.32 M</p> Signup and view all the answers

    Study Notes

    Freezing Point Depression and Boiling Point Elevation

    • Freezing point depression is calculated using the equation ∆Tf = -iKfm.
    • Boiling point elevation is calculated using the equation ∆Tb = iKbm.
    • The molality is calculated by dividing the moles of solute by the kilograms of solvent.
    • The change in temperature is calculated by multiplying the van't Hoff factor (i), the molal freezing point depression constant (Kf) or boiling point elevation constant (Kb), and the molality.
    • For example, a 5.37 m solution of a non-electrolyte in water will experience a freezing point depression of -10.0 oC and a boiling point elevation of 2.7 oC.
    • The final freezing point will be -10.0 oC and the final boiling point will be 102.7 oC.

    Solubility

    • The larger the gas, the more soluble it will be in water.
    • Larger gas particles have a greater surface area, which allows them to interact more strongly with the water molecules.
    • Polar organic molecules dissolve in water better than nonpolar organic molecules.
    • Hydrogen bonding increases solubility.
    • C–C and C–H bonds are not very polar, which makes them less soluble in water.
    • Liquids that mix in all proportions are miscible.
    • Liquids that do not mix are immiscible.
    • Hexane is nonpolar and water is polar, so they are immiscible.

    Biological Importance of Solubility

    • Fat-soluble vitamins, like vitamin A, are nonpolar and readily stored in fatty tissue in the body.
    • Water-soluble vitamins, like vitamin C, need to be included in the daily diet since they are not stored in the body.
    • The solubility and polarity of molecules are important for biological processes.

    Pressure Effects on Solubility

    • The solubility of solids and liquids are not appreciably affected by pressure.
    • The solubility of gases is affected by pressure.

    Henry's Law

    • The solubility of a gas is proportional to the partial pressure of the gas above the solution. - If you double the partial pressure of a gas over a liquid at constant temperature, there will be twice as many gas molecules in the liquid.
    • The Henry's law constant is not affected by changes in pressure.
    • The Henry's law constant is a proportionality constant that is unique to each gas and solvent system.

    Van't Hoff Factor

    • The van't Hoff factor (i) takes into account dissociation in solution.
    • For example, a 1.00 m solution of NaCl in water will have a van't Hoff factor of 2, as NaCl dissociates into two ions (Na+ and Cl-) in solution.
    • The exact amount that particles remain together is dependent on the concentration.

    Azeotropes

    • Azeotropes are solutions where the components exist in the same mole fraction in the liquid and vapor phase at a particular concentration.
    • Once an azeotropic composition is reached, the samples cannot be separated further by distillation.
    • Other physical methods are needed to separate azeotropic mixtures.

    Osmosis

    • Osmosis is the net movement of solvent molecules from a solution of low to high concentration across a semipermeable membrane.
    • The applied pressure to stop osmosis is called osmotic pressure.
    • Osmotic pressure is calculated using the equation π = iMRT, where:
      • π = osmotic pressure
      • i = van't Hoff factor
      • M = molarity
      • R = ideal gas constant
      • T = temperature in Kelvin.

    Types of Solutions and Osmosis

    • Isotonic solutions have the same osmotic pressure and solvent passes the membrane at the same rate both ways.
    • Hypotonic solutions have lower osmotic pressure and solvent leaves this solution at a higher rate than it enters with.
    • Hypertonic solutions have higher osmotic pressure and solvent enters this solution at a higher rate than it leaves with.

    Osmosis and Blood Cells

    • Red blood cells have semipermeable membranes.
    • If red blood cells are stored in a hypertonic solution, they will shrivel as water leaves the cell; this is called crenation.
    • If red blood cells are stored in a hypotonic solution, they will grow until they burst; this is called hemolysis.

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    Description

    This quiz covers concepts of freezing point depression and boiling point elevation in chemistry. You'll learn to apply formulas related to molality and understand the principles of solubility. Explore solutions and their effects on temperature changes.

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