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Chemistry of solutions
 

Chemistry of solutions

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    Chemistry of solutions Chemistry of solutions Presentation Transcript

    • D’ CHEMISTRY OF
      SOLUTIONS
    • SOME DEFINITIONS
      A solution is a _______________ mixture of 2 or more substances in a single phase.
      One constituent is usually regarded as the SOLVENTand the others as SOLUTES.
    • SOME DEFINITIONS
      • Solutions are homogeneous mixtures of two or more pure substances.
      • In a solution, the solute is dispersed uniformly throughout the solvent.
    • PARTS OF A SOLUTION
      SOLUTE – the part of a solution that is being dissolved
      (usually the lesser amount)
      SOLVENT – the part of a solution that dissolves the solute
      (usually the greater amount)
      Solute + Solvent = Solution
      O2
      N2
      NH3
      H2O
      H2O
      Isopropyl alcohol
      H2O
      Ethyl alcohol
      Iodine
      Alcohol
      H2O
      Salt
    • WHICH IS WHICH 1st ROUND
      • Identify the solute and solvent in each of the following solutions.
      • 1.0 g of sugar dissolved in 100 g of water.
      • 50 mL of water mixed with 20 mL isopropyl alcohol
      • A tincture of Iodine is prepared with 0.10 g I2 and 10.0 mL of ethyl alcohol.
      • 40 % ethanol a rubbing alcohol.
      • Sugar is the smaller quantity that is dissolving. Therefore it the solute and water is the solvent.
      • Since both water and isopropyl alcohol are liquids, the one smaller volume, is the solute and water is the solvent.
      • Iodine is the solute and ethyl alcohol is the solvent.
      • Ethanol is the solvent and water is the solute.
    • WHICH IS WHICH 2nd ROUND
      • Identify the solute and solvent in each of the following solutions.
      • 10 g NaCl and 100 g of water.
      • 50 mL ethanol and 10 mL H2O
      • 2.0 L oxygen and 8.0 L nitrogen.
      • 100 g silver and 40 g mercury.
      • 100 mL H2O and 5.0 g sugar
    • TYPE OF SOLUTION
      • Gas
      • Liquid
      • Solid
    • SOME EXAMPLES OF SOLUTION
      Air
      Oxygen
      Nitrogen
      H2O
      CO2
      Soda water
      H2O
      Vinegar
      Acetic acid
      H2O
      Sugar
      Sugar syrup
      Ag
      Hg
      Dental
      amalgam
      Brass or
      Steel
      Carbon
      Zinc
      Iron
      Copper
    • D’ UNIVERSAL SOLVENT
      WATER
      H2O
    • HOW SOLUTIONS ARE
      FORMED?
    • DEFINE SOLUTIONS
      • Solutions are homogeneous mixtures of two or more pure substances.
      • In a solution, the solute is dispersed uniformly throughout the solvent.
    • How Does a Solution Form?
      Solvent molecules attracted to surface ions.
      Each ion is surrounded by solvent molecules.
      Enthalpy (DH) changes with each interaction
      broken or formed.
      Ionic solid dissolving in water
      • The ions are solvated
      (surrounded by solvent).
      • If the solvent is water, the ions are hydrated.
      • The intermolecular forces.
      How Does a Solution Form?
      • solvation is an interaction of a solute with the solvent, which leads to stabilization of the solute in the solution.
      What is solvation?
    • KINDS OF SOLUTION
      • Dilute
      small amount of solute dispersed in the solvent
      • Concentrated
      large amount of solute is dissolved in the solvent
    • Types of Solutions Based on Solute Concentration…
      • Hypotonic
      (lower solute concentration) to the solution
      • Hypertonic
      (higher solute concentration) to the solution
      • Isotonicsolutions are equal in their solute concentrations. We say that they
      are isotonic to each other.
      Types of Solutions Based on Solute Concentration…
    • QUESTIONS THAT NEEDS SOLUTIONS…
      • How does a solid dissolve into a liquid?
      • What ‘drives’ the dissolution process?
      • What are the energetics of dissolution?
    • WHAT IS DISSOLUTION ?
      is the process by which a solid, 
      liquid or gas 
      forms a solution 
      in a solvent.
    • DISSOLUTION PROCESS IN SOLIDS…
      In solids this can be explained as the breakdown of the crystal lattice into individual ions, atoms or molecules and their transport into the solvent.
    • DISSOLUTION PROCESS IN LIQUIDS & GASES…
      For liquids and gases, the molecules must be compatible with those of the solvent for a solution to form.
    • dry
      Dissolution vs Reaction
      NiCl2(s)
      Ni(s) + HCl (aq)
      NiCl2(aq) + H2(g)
      Dissolution is a physical change—you can get back the original solute by evaporating the solvent.
      If you can’t, the substance didn’t dissolve, it reacted.
    • DEFINE
      SOLUBILITY?
    • What is Solubility?
      refers to the maximum amount of solute, expressed in grams, that can be dissolved in 100 g of water at a specific temperature & pressure.
      • Soluble
      a substance that dissolves in a solvent
      • Insoluble
      a substance that does not dissolve in a solvent (sand is insoluble in water)
      VOCABULARY
    • LABORATORY ACTIVITY 2.7SOLUBILITY IN WATER
      INSOLUBLE
      INSOLUBLE
      SOLUBLE
      S/SOLUBLE
      INSOLUBLE
      INSOLUBLE
      SOLUBLE
      S/SOLUBLE
      INSOLUBLE
      INSOLUBLE
      SOLUBLE
      S/SOLUBLE
      INSOLUBLE
      INSOLUBLE
      SOLUBLE
      S/SOLUBLE
      SOLUBLE
      SOLUBLE
      INSOLUBLE
      S/SOLUBLE
      SOLUBLE
      SOLUBLE
      INSOLUBLE
      S/SOLUBLE
      INSOLUBLE
      INSOLUBLE
      SOLUBLE
      S/SOLUBLE
      INSOLUBLE
      INSOLUBLE
      SOLUBLE
      S/SOLUBLE
    • VOCABULARY
      • Immiscible
      Two liquids that are insoluble
      (Oil & Vinegar)
      • Miscible
      Two liquids that are soluble in each other
      (Alcohol & Water)
      IMMISCIBLE
      MISCIBLE
      MISCIBLE
      S/MISCIBLE
      • Saturated solution
      • Solvent holds as much solute as is possible at that temperature.
      • Undissolved solid remains in flask.
      • Dissolved solute is in dynamic equilibrium with solid solute particles.
      Degree of Saturation
    • Degree of Saturation
      • Unsaturated Solution
      • Less than the maximum amount of solute for that temperature is dissolved in the solvent.
      • No solid remains in flask.
    • Degree of Saturation
      • Supersaturated
      • Solvent holds more solute than is normally possible at that temperature.
      • These solutions are unstable; crystallization can often be stimulated by adding a “seed crystal” or scratching the side of the flask.
    • FACTORS AFFECTING
      SOLUBILITY
    • Factors Affecting Solubility
      Chemists use the axiom
      “like dissolves like”
      • Polar substances tend to dissolve in polar solvents.
      • Nonpolar substances tend to dissolve in nonpolar solvents.
    • LABORATORY ACTIVITY 2.8FACTORS SOLUBILITY
      IMMISCIBLE
      MISCIBLE
      MISCIBLE
      S/MISCIBLE
      SOLUBLE
      SOLUBLE
      INSOLUBLE
      INSOLUBLE
    • Temperature
      Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.
    • LABORATORY ACTIVITY 2.8FACTORS SOLUBILITY
      TAKES TIME
      TO DISSOLVE
      EASILY
      DISSOLVED
      TAKES TIME
      TO DISSOLVE
      EASILY
      DISSOLVED
      TAKES TIME
      TO DISSOLVE
      EASILY
      DISSOLVED
    • Temperature
      • The opposite is true of gases.
      Higher temperature drives gases out of solution.
      • Carbonated soft drinks are more “bubbly” if stored in the refrigerator.
      • Warm lakes have less O2 dissolved in them than cool lakes.
    • Molecular Size
      • The larger the molecules of the solute are, the larger is their molecular weight and their size.
      • It is more difficult it is for solvent molecules to surround bigger molecules.
      • If all of the above mentioned factors all excluded, a general rule can be found that larger particles are generally less soluble. 
      • If the pressure, and temperature are the same than out of two solutes of the same polarity, the one with smaller particles is usually more soluble.
    • LABORATORY ACTIVITY 2.8FACTORS SOLUBILITY
      TAKES TIME
      TO DISSOLVE
      EASILY
      DISSOLVED
      TAKES TIME
      TO DISSOLVE
      EASILY
      DISSOLVED
    • Effect of Stirring
      • Stirring only increases the speed of the process - it increases the movement of the solvent that exposes solute , thus enabling solubility.
      • As molecules in liquid substances are in constant move, the process would take place anyway, but it would take more time.
    • LABORATORY ACTIVITY 2.8FACTORS SOLUBILITY
      DISSOLVES
      FASTER
      TAKES TIME
      DISSOLVES
      DISSOLVES
      FASTER
      TAKES TIME
      DISSOLVES
    • Factors Affecting Solubility
      The stronger the intermolecular attractions between solute and solvent, the more likely the solute will dissolve.
      Example: ethanol in water
      Ethanol = CH3CH2OH
      Intermolecular forces = H-bonds; dipole-dipole; dispersion
      Ions in water also have ion-dipole forces.
    • Factors Affecting Solubility
      • Glucose
      (which has hydrogen bonding) is very soluble in water.
      • Cyclohexane
      (which only has dispersion forces)is not water-soluble.
    • Factors Affecting Solubility
      Vitamin A is soluble in nonpolar compounds
      (like fats).
      Vitamin C is soluble in water.
    • Which vitamin is water soluble and which is fat soluble?
      HEALTHAPPLICATION
    • Gases in Solution
      In general, the solubility of gases in water increases with increasing mass.
      Why?
      Larger molecules have stronger dispersion forces.
    • Gases in Solution
      The solubility of liquids and solids does not change appreciably with pressure.
      But, the solubility of a gas in a liquid is directly proportional to its pressure.
      Increasing pressure above solution forces more gas to dissolve.
    • Henry’s Law
      States that:
    • Henry’s Law
      Sg = kPg
      Where:
      Sg is the solubility of the gas;
      k is the Henry’s law constant for that gas in that solvent;
      Pgis the partial pressure of the gas above the liquid.