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SOLUTIONS and SOLUBILITY
Know for test 1. Definition mixture solution solute solvent solubility dilute concentrated
MIXTURE: Two or more substances existing together that can be separated by physical means such as filtration or raising or lowering the temperature. The substances do not form chemical bonds.
SOLUTION: A homogeneous mixture consisting of a substance that is evenly distributed throughout another substance.
SOLUTE: A substance that is dissolved in another substance. SOLVENT: A substance that dissolves another substance. The compound in the largest percentage is the solvent
SOLUBILITY: Amount of solute that can dissolve in a solvent at a given temperature, or the maximum amount of grams of a solute that will dissolve in 100 mL of solvent at a certain temperature.
CONCENTRATION: Comparative amounts of solute in a solvent DILUTE: Small amount of solute in the solvent CONCENTRATED: Large amount of solute in the solvent We ll consider anything greater than a 6 molar (6M) solution as concentrated
Answer the following: 2B turned in 1. Is a 5 molar solution of sulfuric acid dilute or concentrated? 2. Name for maximum amount of solute that will dissolve in 100 mL of solvent at a given temperature. 3. Is a solution a heterogeneous or homogeneous mixture?
Know for test 2. Define Rate of dissolution Dissociation Ionization Electrolytes Nonelectrolytes 3. In a solution pick the solute and solvent based on ratios
RATE OF DISSOLUTION: How fast a solute dissolves in a solvent. DISSOCIATION: Separation of an ionic compound into ions in water.
IONIZATION: Separation of a polar covalent substance into ions by water. Water pulls the molecules apart.
ELECTROLYTE: A substance that separates into ions or forms ions in a water solution and allows electricity to flow through the solution. Examples: NaCl - separates into ions; HCl - forms ions
NONELECTROLYTE: A substance that does not separate into or form ions in a water solution and does not allow electricity to flow through the solution.
I. The ratio of the compounds involved in a solution determines which substance is the solvent and which substance is the solute.
A. Is it a solvent or a solute? 1. The substance present in the higher percentage is the solvent. 2. The substance present in the lower percentage is the solute.
Answer the following: 2B turned in 4. In a solution made of 78% nitrogen, 21% oxygen,.09% argon, and.01% other gases which is the solvent? 5. Sulfuric acid is a polar covalent molecule that when placed in water breaks apart into positive and negative charges, is this process called dissociation or ionization? 6. When sodium chloride is placed in water electricity can be conducted, is this dissociation or ionization?
Know for test 4. Conditions for dissolving 5. Know alloys Bronze Nickel Sterling silver Brass 6. Factors affecting rate of dissolving
II. LIKE DISSOLVES LIKE
1. Ionic compounds dissolve only ionic compounds. 2. Nonpolar solvents will dissolve only nonpolar solutes - kerosene dissolves grease.
3. Water is polar. (Polar compounds have partial positive and negative charges, called dipoles.)
Water will dissolve:
a. Other polar covalent compounds like sugar or HCl b. Ionic compounds like salt (NaCl) c. The hydrogen and oxygen dipoles in water are attracted to the positive and negative charges of the ions in the ionic compound.
4. Some molecules have a polar end and a nonpolar end. a. They will combine with either polar or nonpolar substances.
b. Alcohols are both polar and nonpolar. Ethanol will combine with iodine (I 2 is nonpolar) on the nonpolar end and water on the polar end.
c. Soaps and detergents remove oil because the nonpolar molecule ends combine with oils and the polar molecule ends combine with water to pull the oils into solution.
II. The type of solvent determines what type of solution is formed.
A. Solid solutions are a solid solute dissolved in a solid solvent.
1. Composed of two or more solids - usually metal alloys 2. Made by melting the solids and mixing them together
3. Bronze is tin (along with zinc, lead or silver) dissolved in copper 4. Nickel coins are copper dissolved in nickel
5. Sterling silver is copper (7.5%) dissolved in silver (92.5%) 6. Brass is zinc dissolve in copper
B. Liquid solutions are a solid, liquid or gas solute dissolved in a liquid solvent.
1. Tincture of iodine is iodine (a solid) dissolved in alcohol - a solid in a liquid
2. Lemonade is sugar and lemon juice dissolved in water - a solid and a liquid dissolved in a liquid.
3. Vinegar is acetic acid dissolved in water - a liquid in a liquid
4. Rubbing alcohol is isopropyl alcohol dissolved in water – a liquid in a liquid
5. Ocean water is many types of salts and gases dissolved in water - solids and gases dissolved in a liquid.
6. Seltzer is carbon dioxide dissolved in water - a gas in a liquid
7. The solvent and the solute must be the same type of chemical compound (ionic, polar or nonpolar).
C. Gaseous solutions are gas solutes dissolved in a gas solvent.
1. Air is various gases dissolved in nitrogen a. 78% nitrogen b. 21% oxygen c. 0.9% argon d. 0.03% carbon dioxide
2. Trace amounts of hydrogen, ozone, methane, carbon monoxide, helium, neon, krypton, xenon, and varying amounts of water vapor
2. Divers use a solution of oxygen and helium dissolved in nitrogen in their air supply tanks.
III. The solubility and rate of dissolving for a solute depends upon:
A. The surface area of the solid
1. The larger the surface area, the faster the solute is dissolved. 2. A 10 gram cube has less surface area than 10 grams of powder.
3. Smaller particles mean increased surface area of solute covered by the solvent, causing the solute to dissociate into ions or the molecules of solute to ionize more quickly.
10 x 10 CUBE 100, 1 x 1 CUBES
B. Stirring or agitation increases energy and brings more fresh solvent in contact with the solute.
1. Stirring lemonade causes the sugar to dissolve faster and the lemon juice to disperse more quickly. 2. Water erodes rock more quickly at waterfalls, rapids, and eddies.
C. The temperature of the solvent - increased temperature means increased energy.
1. Increasing temperature increases the rate of dissociation of the solid
2. Warmer particles move faster a. Causing the solvent particles to collide more frequently with the solid
b. Faster moving particles have greater energy c. This causes solute particles to break off more rapidly
D. The pressure applied to the solute and temperature of the solvent affect solubility in gases.
1. Soda pop is produced by a.Cooling the soda syrup b.Pressurizing the carbon dioxide
c. The carbon dioxide stays in solution until the pressure in the bottle or can is released.
2. The best fishing grounds are found in northern waters – fresh or salt water
a. The water is colder. b. It can hold more dissolved gases (oxygen) than when it is warmer.
3. Thermal pollution in bodies of water causes less oxygen to be available for organisms
a. El Nino caused a rise in ocean temperatures near Australia causing a die off in the populations of corals in the Great Barrier Reef.
b. Rising temperatures off the coast of Florida have caused a massive die off in corals and fish populations.
c. Many nuclear power plants release warm water and have caused a change in the flora and fauna that are found downstream of their outlet pipes. Fish and plant life now found in these streams are usually found in streams much further south.
Answer the following 7. Name three methods that will increase the rate of solubility. 8. Name for a solution of copper, tin, and silver. 9. Which of the following will increase the solubility of a gas in a liquid? Increased surface area, increased pressure, increased temperature, stirring
IV. Solubility of substances
A. The solubility of a compound refers to the maximum number of grams of a substance that will dissolve in 100 grams of solvent at a certain temperature.
B. Solubility for solid solutes is dependent upon the temperature of the solvent
C. Solubility for gas solutes is dependent on the solvent temperature and the pressure applied to the gas.
D. SOLUBILITY TABLES give the solubility of a solute in a solvent at different temperatures.
SOLUBILITY of COMPOUNDS in GRAMS per 100 GRAMS OF WATER at DIFFERENT TEMPERATURES
E. SOLUBILITY CURVES are line graphs of solubility.
1. They are used to determine the amount of solute that will go into solution at a given temperature displayed in the graph.
2. Interpolate the graph to find the temperature or the amount of solute.
3. Do not extrapolate; solubility curves often do not stay constant
Answer the following 10. On the following graph how many grams of Potassium chloride will dissolve in 100 mL of water at 40 degrees Celsius?
Answer the following 11. On the following chart what temperature is required to dissolve 150g of silver nitrate in 100mL of water?
V. Unsaturated, Saturated, and Supersaturated solutions
A. Saturation depends upon temperature and has to be specified whenever the saturation of a liquid or gas solution is discussed.
1. Usually the reference temperature is room temperature (20 C or 72 F).
can dissolve in it increases 2. As the temperature of the solvent increases, the amount of solid solute that can dissolve in it increases.
3. As the temperature of a solvent decreases, the amount of solid solute that can dissolve in it decreases.
4. Saturation values are often expressed as percentages, but more precisely as grams of solute per 100 grams of solvent (g/100g).
5. Saturation values for water solutions are expressed as grams per 100 mL or 100 grams of water. Water has a mass of 1 gram per 1 mL of volume; the measurement system was set up this way.
B. Unsaturated solutions: 1. Any solution that can dissolve more solute at a given temperature is unsaturated.
2. More solute can be dissolved in the solvent at the specified temperature. 3. No undissolved solute is visible in the container.
4. Each time a saturated solution is heated to a higher temperature it becomes unsaturated.
5. Unsaturated is an imprecise term – the amount of solute can be anything less than the saturated amount for the specified temperature.
C. Saturated solutions: 1. Solutions that have dissolved all of the solute that they can hold at a certain temperature.
2. No more solute can be dissolved in the solvent at the specified temperature. 3. Undissolved solute is still visible in the container.
D. Supersaturated solutions: 1. More solute is in solution than the solvent can normally dissolve at the specified temperature.
2. No undissolved solute is visible in the container
3. Supersaturated solutions are obtained by: a. Raising the temperature of a saturated solvent until the solute dissolves completely
b. Cooling the solution to the specified temperature. c. The solute will remain in solution if allowed to cool slowly and not shaken or disturbed in any way.
4. A supersaturated solution is unstable and crystals will form if a. The solution is agitated (shaken or stirred) b. The solution contacts other crystals
Answer the following 12. On the following chart what is the saturation state of a solution containing 80g of KBr at 30° Celcius?
VI. CONCENTRATION - the amount of solute in a solution
A. Concentrated and dilute are not precise terms. Sometime we need to know how concentrated a solution really is.
B. Precise concentrations are expressed in percentages. C. Concentration of a solid dissolved in a liquid is expressed as percentage by mass
Examples: Remember: 1 g of water = 1 mL of water
A potassium chloride solution contains 88 grams of KCl in 1.0 L of solution. How many grams of solute are in 50 mL of the same solution?
Steps to the answers: 1. Change Liters to mL using 1.0 L = 1000 mL
Use the following mass = SOLUTE grams/mL X SOLUTION mL = TOTAL SOLUTE grams 88g/1000mL x 50 mL = 4.4 g
Answer the following 13. Use the following chart to determine how many grams of KBr would be required to saturate a solution in 300 mL of water at 70 degrees Celcius
D. The concentration of two liquids in a solution is expressed in percentage by volume.
Examples: 1. Juice drinks are usually 10% juice and 90% water. If there is 100 mL of drink in a box, how much of the drink is juice and how much is water?
The drink contains 10 mL juice (10% of 100 mL) and 90 mL water (90% of 100 mL).
Answer the following 14. How many milliliters of isopropyl alcohol are in 300 mL of a 70% solution?
VII. Ion formation in water solutions
A. Dissociation of ionic compounds in water: 1. Positive and negative ions separate in water in a process called dissociation
2. Dissociation is due to a. The negative partial charge of the oxygen atom in the water molecule attracting the positive ion in the compound.
b. The positive partial charges on the hydrogen atoms in the water molecule attracting the negative ion in the compound.
c. The force of attraction between the partial charges of the water molecules and the ionic particles in the compound is strong enough to break the bonds holding the ionic compound together.
B. Ionization of polar covalent substances in water
1. Polar covalent compounds can be pulled apart by water in a process called ionization
2. Ionization is due to a. The oppositely charged poles of the compound and water molecules attracting each other.
b. The force of attraction for the water is so high that atoms are pulled from the solute by the water molecules forming ions.
Answer the following 15. Sulfuric acid is a polar covalent molecule that breaks into a hydrogen cation and sulfate anion when placed in water. Is this process called dissociation or ionization? 16. NaCl separates into a sodium cation and chlorine anion when placed in water. Is this process called dissociation or ionization?
VIII. Effects of solute particles on a solvent(colligative properties
A. Pure water does not conduct electricity – nonelectrolyte B. Some particles in solution cause water to conduct electricity because they form electrolytes.
1. Both dissociation and ionization cause the water to conduct electricity because of the formation of ions that are called electrolytes in a solution.
2. Many polar compounds are nonelectrolytes in solution because they do not ionize in water.
C. Solute particles interfere with the organization of the solvent particles.
1. This interference lowers the temperature required to freeze the solvent for example: antifreeze or salt added to water lower the freezing point of water.
2. The interference raises the boiling point of the solvent also.
a. The solute interferes with the evaporation of the solvent b. More energy is needed to allow the solvent to evaporate c. Example: antifreeze or salt raises the boiling point of water
3. The size of the changes in the freezing and boiling points depends on the amount of solute in the solvent (concentration) **number of particles determine size of changes
Above a solution are solvent particles that have entered a gaseous state that create a vapor pressure above the solution in a closed container. This vapor pressure slows down the rate that state changes take place (liquid to gas, solid to gas) Increased numbers of solute particles lower the vapor pressure above the solution
Colligative properties: depend on number of solute particles 1. Freezing point depression 2. Boiling point elevation 3. Vapor pressure lowering
Answer the following 17. Name three colligative properties