Solubility Curve RECALL TYPES OF MIXTURES: SUSPENSIONS COLLOIDS SOLUTIONS All mixtures are physically combined and can be physically separated. DEFINITION A solution is a homogeneous mixture of two or more substance in a single physical state Solution a mixture of two or more substances that is identical throughout can be physically separated composed of solutes and solvents the substance in the smallest amount and the one that dissolves in the solvent Iced Tea Mix (solute) Salt water is considered a solution. How can it be physically separated? the substance in the larger amount that dissolves the solute Iced Tea (solution) Water (solvent) Colloids (milk, fog, jello) are considered solutions Solutes Change Solvents The amount of solute in a solution determines how much the physical properties of the solvent are changed Examples: Lowering the Freezing Point The freezing point of a liquid solvent decreases when a solute is dissolved in it. Ex. Pure water freezes at 320F (00C), but when salt is dissolved in it, the freezing point is lowered. This is why people use salt to melt ice. Raising the Boiling Point The boiling point of a solution is higher than the boiling point of the solvent. Therefore, a solution can remain a liquid at a higher temperature than its pure solvent. Ex. The boiling point of pure water is 2120F (1000C), but when salt is dissolved in it, the boiling point is higher. This is why it takes salt water longer to boil than fresh water. TYPES OF SOLUTIONS SOLUTE GAS SOLVENT GAS EXAMPLE Air GAS LIQUID Seltzer (CO2) LIQUID LIQUID Antifreeze (ethyl glycol in water) SOLID LIQUID Sea water ( salt in water) GAS SOLID Charcoal filter (poisonous gases in carbon) LIQUID SOLID Dental filling (mercury in silver) SOLID SOLID Sterling silver (copper in silver) SOLID SOLUTION Contain two or more metals called alloys Formed by melting the components and mixing them together and allowing them to cool Properties of alloys are different from the original component metals TYPES OF ALLOYS ALLOY Babbitt COMPONENT Tin, antimony, copper USES Bearings Bell metal Coinage metals 16 karat gold Copper, tin Bells Copper, tin, zinc Coins Gold, copper, silver Jewelry Sterling Nichrome Silver, copper Nickel, iron, chromium, manganese Jewelry, flatware Heating elements Important terminologies: Soluble – substance that dissolves another substance Insoluble – substance that does not dissolve another substance Solutes Change Solvents The amount of solute in a solution determines how much the physical properties of the solvent are changed Examples: Lowering the Freezing Point The freezing point of a liquid solvent decreases when a solute is dissolved in it. Ex. Pure water freezes at 320F (00C), but when salt is dissolved in it, the freezing point is lowered. This is why people use salt to melt ice. Raising the Boiling Point The boiling point of a solution is higher than the boiling point of the solvent. Therefore, a solution can remain a liquid at a higher temperature than its pure solvent. Ex. The boiling point of pure water is 2120F (1000C), but when salt is dissolved in it, the boiling point is higher. This is why it takes salt water longer to boil than fresh water. SOLUBILITY Solubility Solubility maximum grams of solute that will dissolve in 100 g of solvent at a given temperature varies with temp based on a saturated solution Solubility UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form increasing concentration Concentration the amount of solute dissolved in a solvent at a given temperature •described as unsaturated if it has a low concentration of solute •described as saturated if it has a high concentration of solute •described as supersaturated if contains more dissolved solute than normally possible C. Determine if a solution is saturated, unsaturated, or supersaturated. • If the solubility for a given substance places it anywhere on it's solubility curve it is saturated. • If it lies above the solubility curve, then it's supersaturated, • If it lies below the solubility curve it's an unsaturated solution. Remember though, if the volume of water isn't 100 cm3 to use a proportion first as shown above. Solubility how much solute dissolves in a given amt. of solvent at a given temp. KNO3 (s) SOLUBILITY CURVE KCl (s) Solubility (g/100 g H2O) HCl (g) Temp. (oC) Unsaturated: solution could hold more solute; below line Saturated: solution has “just right” amt. of solute; on line Supersaturated: solution has “too much” solute dissolved in it; above the line Solubility vs. Temperature for Solids 140 KI 130 120 shows the dependence of solubility on temperature Solubility (grams of solute/100 g H2O) Solubility Table 110 NaNO3 gases solids 100 KNO3 90 80 HCl NH4Cl 70 60 NH3 KCl 50 40 30 NaCl KClO3 20 10 SO2 0 10 20 30 40 50 60 70 80 90 100 LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517 Solubility • Solids are more soluble at... – high temperatures. Gases are more soluble at... • low temperatures & • high pressures (Henry’s Law). • EX: nitrogen narcosis, the “bends,” soda How to use a solubility graph? A. IDENTIFYING A SUBSTANCE ( given the solubility in g/100 cm3 of water and the temperature) • Look for the intersection of the solubility and temperature. Example:What substance has a solubility of 90 g/100 3 cm of water at a temperature of 25ºC ? Example: What substance has a 3 solubility of 200 g/100 cm of water at a temperature of 90ºC ? B. Look for the temperature or solubility •Locate the solubility curve needed and see for a given temperature, which solubility it lines up with and visa versa. What is the solubility of potassium nitrate at 80ºC ? At what temperature will sodium nitrate have a solubility of 95 g/100 cm3 ? At what temperature will potassium iodide have a solubility of 230 g/100 cm3 ? What is the solubility of sodium chloride at 25ºC in 150 cm3 of water ? • From the solubility graph we see that sodium chlorides solubility is 36 g. Place this in the proportion below and solve for the unknown solubility. Solve for the unknown quantity by cross multiplying. Solubility in grams = unknown solubility in grams 100 cm3 of water other volume of water ___36 grams____ = unknown solubility in grams 100 cm3 of water 150 cm3 water The unknown solubility is 54 grams. You can use this proportion to solve for the other volume of water if you're given the other solubility. Solids and Gases dissolved in Liquids Solids dissolved in liquids Sol. Gases dissolved in liquids Sol. To As To , solubility To As To , solubility How many additional grams of solute must be added in order to make it saturated? From the graph you can see that the solubility for potassium nitrate at 50ºC is 84 grams If there are already 30 grams of solute in the solution, all you need to get to 84 grams is 54 more grams ( 84g-30g ) Solubility vs. Temperature for Solids 140 KI 130 120 shows the dependence of solubility on temperature Solubility (grams of solute/100 g H2O) Solubility Table 110 NaNO3 gases solids 100 KNO3 90 80 HCl NH4Cl 70 60 NH3 KCl 50 40 30 NaCl KClO3 20 10 SO2 0 10 20 30 40 50 60 70 80 90 100 LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517 Solubility vs. Temperature for Solids 140 KI Classify as unsaturated, saturated, or supersaturated. 130 120 NaNO3 80 g NaNO3 @ 30oC =unsaturated per 100 g H2 O 60 g KCl @ 60oC =saturated 50 g NH3 @ 10oC = unsaturated 70 g NH4Cl @ 70oC =supersaturated Solubility (grams of solute/100 g H2O) 110 gases solids 100 KNO3 90 80 HCl NH4Cl 70 60 NH3 KCl 50 40 30 NaCl KClO3 20 10 SO2 0 10 20 30 40 50 60 70 80 90 100 Solubility vs. Temperature for Solids 140 KI 130 120 Per 500 g H2O, 120 g KNO3 @ 40oC 110 NaNO3 gases saturation point @ 40oC for 100 g H2O = 66 g KNO3 So sat. pt. @ 40oC 120 g < 330 g for 500 g H2O = 5 x 66 g = 330 g unsaturated Solubility (grams of solute/100 g H2O) solids 100 KNO3 90 80 HCl NH4Cl 70 60 NH3 KCl 50 40 30 NaCl KClO3 20 10 SO2 0 10 20 30 40 50 60 70 80 90 100 Describe each situation below. (A) Per 100 g H2O, 100 g Unsaturated; all solute NaNO3 @ 50oC. dissolves; clear solution. (B) Cool solution (A) very Supersaturated; extra slowly to 10oC. solute remains in solution; still clear. (C) Quench solution (A) in Saturated; extra solute an ice bath to 10oC. (20 g) can’t remain in solution, becomes visible.