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 the substance in the larger amount that dissolves the solute Colloids (milk, fog, jello) are considered solutions Iced Tea Mix (solute) Water (solvent) Iced Tea (solution) Salt water is considered a solution. How can it be physically separated?

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 32 0 F (0 0 C), 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 F (100 0 C), 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 SOLUTESOLVENTEXAMPLE GAS Air GASLIQUIDSeltzer (CO 2 ) LIQUID Antifreeze (ethyl glycol in water) SOLIDLIQUIDSea water ( salt in water) GASSOLIDCharcoal filter (poisonous gases in carbon) LIQUIDSOLIDDental filling (mercury in silver) 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 ALLOYCOMPONENTUSES BabbittTin, antimony, copper Bearings Bell metalCopper, tinBells Coinage metalsCopper, tin, zincCoins 16 karat goldGold, copper, silverJewelry SterlingSilver, copperJewelry, flatware NichromeNickel, iron, chromium, manganese 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 32 0 F (0 0 C), 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 F (100 0 C), 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 SATURATED SOLUTION no more solute dissolves UNSATURATED SOLUTION 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 ifsupersaturated 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 cm 3 to use a proportion first as shown above.

Temp. ( o C) Solubility (g/100 g H 2 O) KNO 3 (s) KCl (s) HCl (g) SOLUBILITY CURVE Solubility  how much solute dissolves in a given amt. of solvent at a given temp. below Unsaturated: solution could hold more solute; below line on Saturated: solution has “just right” amt. of solute; on line Supersaturated: solution has “too much” solute dissolved in it; above the line

Solubility Table LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World, 1996, page Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KI KCl NaNO 3 KNO 3 HClNH 4 Cl NH 3 NaCl KClO 3 SO 2 shows the dependence of solubility on temperature gases solids

Solubility Solids are more soluble at... 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 cm 3 of water and the temperature) Look for the intersection of the solubility and temperature.

Example:What substance has a solubility of 90 g/100 cm 3 of water at a temperature of 25ºC ?

Example: What substance has a solubility of 200 g/100 cm 3 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 cm 3 ?

At what temperature will potassium iodide have a solubility of 230 g/100 cm 3 ?

What is the solubility of sodium chloride at 25ºC in 150 cm 3 of water ? From the solubility graph we see that sodium chlorides solubility is 36 g.

Solubility in grams=unknown solubility in grams 100 cm 3 of waterother volume of water ___36 grams____=unknown solubility in grams 100 cm 3 of water150 cm 3 water Place this in the proportion below and solve for the unknown solubility. Solve for the unknown quantity by cross multiplying. 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 ToTo Sol. ToTo Solids dissolved in liquids Gases dissolved in liquids As T o, 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 Table LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World, 1996, page 517 shows the dependence of solubility on temperature Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KI KCl NaNO 3 KNO 3 HClNH 4 Cl NH 3 NaCl KClO 3 SO 2 gases solids

Classify as unsaturated, saturated, or supersaturated. per 100 g H 2 O 80 g NaNO 30 o C 60 g 60 o C=saturated 50 g NH 10 o C = unsaturated 70 g NH 4 70 o C =unsaturated =supersaturated Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KI KCl NaNO 3 KNO 3 HClNH 4 Cl NH 3 NaCl KClO 3 SO 2 gases solids

So sat. 40 o C for 500 g H 2 O = 5 x 66 g = 330 g 120 g < 330 g unsaturated saturation 40 o C for 100 g H 2 O = 66 g KNO 3 Per 500 g H 2 O, 120 g KNO 40 o C Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KI KCl NaNO 3 KNO 3 HClNH 4 Cl NH 3 NaCl KClO 3 SO 2 gases solids

(A) Per 100 g H 2 O, 100 g Unsaturated; all solute NaNO 50 o C. dissolves; clear solution. (B) Cool solution (A) very Supersaturated; extra slowly to 10 o C. solute remains in solution; still clear. Describe each situation below. (C) Quench solution (A) in Saturated; extra solute an ice bath to 10 o C. (20 g) can’t remain in solution, becomes visible.