Section 1C.1 & C.2 Reading Solubility Curves

What is Solubility? Solubility: Solubility: the maximum amount of solute that will dissolve in a certain amount of solvent at a given temperature Solute Solute = substance dissolved Solvent Solvent = does the dissolving Example: __ grams of salt (NaCl) in 100 g of water at __ ˚C.

Temperature and Solubility Temperature Temperature affects how much of the solute can be dissolved by the solvent. does not always  Note: Increasing the temperature does not always increase the solubility…think about what happens to dissolved gas in your soda when its heated Solubility curves Solubility curves: used to show how the solubility of a substance changes with temperature.

To read the graph: 1. Find the line for the substance. 2. The amount that dissolves at a given temp. is on the y- axis.

How much KNO 3 dissolves in 100g H 2 O at 50 o C? 1. Find the line (red) 2. Find the temperature and follow up to the line. (green) 3. Read across to the y- axis and this is the answer. (blue) 4. Since it is above the ½-way between 80 and 90, 87g KNO 3 will dissolve.

Types of Solutions: Saturated solution: point on the line  Contains maximum amount of solute at given temp  Contains what it should hold Supersaturated: above the line  Contains more solute than a saturated solution  Contains more than it should hold Unsaturated: below the line is  Contains less solute than saturated solution  Contains less solute than it could hold

. SOLUBILITY GRAPHS Concentration (g/100 g water) temperature NaNO 3 KBr NH 4 Cl KNO 3 Na 2 SO 3 NaCl

SOLUBILITY FORMULAS amount of solute amount of solvent amount of solute amount of solvent = Given solubility unknown

1.The solubility of a solid is 15g / 100g of water. How many grams of the solid must be dissolved in 1 kg of water to make a saturated solution? SOLUBILITY PROBLEMS

amount of solute amount of solvent amount of solute amount of solvent = 15 g g = X g X=150g

SOLUBILITY EXAMPLES 2. If you have 50g in 500g of water, using solubility from problem #1, is the solution saturated? 15g g = X g X=75g is saturated No, 50 g is not saturated!

SOLUBILITY EXAMPLES 3. The solubility of a solute is 5g/100g water at 20 C and 7.5g/100g water at 50 C. How much of the solute must be dissolved in 250g of water at 20 C to prepare a saturated solution? 5g g = X g X=12.5g to prepare a saturated solution

SOLUBILITY EXAMPLES 4. The solubility of a solute is 5g/100g water at 20 C and 7.5g/100g water at 50 C. If a saturated solution is prepared using 200g water at 50 C, then allowed to cool to 20 C: a. Will it still be saturated? b. How much solute will precipitate out?

SOLUBILITY EXAMPLES Will it still be 50 C: 7.5g g = X g X=15g to prepare a saturated 50 C

SOLUBILITY EXAMPLES Will it still be saturated? Now cool it to 20 C: 5g g = X g X=10g to prepare a saturated 20 C

SOLUBILITY EXAMPLES Will it still be saturated? Now cool it to 20 C: 15g > 20 C so its supersaturated!!

SOLUBILITY EXAMPLES How much will precipitate out? 5g g = X g X=10g to prepare a saturated 20 C 7.5g g X g = X=15g to prepare a saturated 50 C

SOLUBILITY EXAMPLES How much will precipitate out? 15g - 10g = 5g will precipitate out!

To do Calculations: To calculate how much extra has been dissolved: Extra = Dissolved amt - saturated in soln (given value) line that temp. To calculate how much more can be dissolved: ? Much more = saturated - given value line that temp

Example 1: How much less KCl is dissolved at 20 o C than at 60 o C in 100g H 2 O? Read the line value: 32g at 20 o C Subtract it from the given value: 45g – 32g = 13 g

Example 2: How much more KCl is required to saturate the solution if 25g are dissolved at 40 o C? Read the line value: 40g Subtract the given value: 40g – 25g = 15 g

Your turn! Use your graph 1. How much NaCl will dissolve in 100g H 2 O at 35 o C? 2. How much NH 4 Cl will dissolve at 50 o C? 3. What is the solubility of SO 2 at 25 o C? 4. What is the solubility of potassium chlorate in 100 grams of water at 35 o C? 5. What is the solubility of potassium iodide in 100 grams of water at 10 o C?

6.What minimum temperature needed to dissolve 80 grams of sodium nitrate in 100 grams of water? 7. What minimum temperature needed to dissolve 42 grams of potassium chloride in 100 grams of water? 8. What minimum temperature needed to dissolve 20 grams of KClO 3 in 100 grams of water? 9.If 95 grams of potassium nitrate are mixed with 100 grams of water at 45ºC, how much will not dissolve? 10.If 85 grams of potassium iodide are mixed with 100 grams of water at 0 º C, how much more must be added to saturate the solution?

11. If 55 grams of potassium chlorate are mixed with 100 grams of water at 55ºC, how much will not dissolve? 12. If 125 grams of potassium iodide are mixed with 100 grams of water at 10ºC, how much more must be added to saturate the solution? 13. What is the solubility of potassium chlorate in 50 grams of water at 35ºC?

14. What is the solubility of potassium chlorate in 100 grams of water at 35 oC? 15. What is the solubility of potassium iodide in 100 grams of water at 10 oC? 16. What is the minimum temperature needed to dissolve 80 grams of sodium nitrate in 100 grams of water? 17. What is the minimum temperature needed to dissolve 42 grams of potassium chloride in 100 grams of water? 18. What is the minimum temperature needed to dissolve 20 grams of KClO3 in 100 grams of water?

19. If 95 grams of potassium nitrate are mixed with 100 grams of water at 45 oC, how much will not dissolve? 20. If 55 grams of potassium chlorate are mixed with 100 grams of water at 55 oC, how much will not dissolve? 21. If 125 grams of potassium iodide are mixed with 100 grams of water at 10 oC, how much more must be added to saturate the solution? 22. If 85 grams of potassium iodide are mixed with 100 grams of water at 0 oC, how much more must be added to saturate the solution? 23. What is the solubility of potassium chlorate in 50 grams of water at 35 oC?

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Practice Molar Mass again! Examples:

Gas Solubility 1C.12 & 1C.13

What About Gases? We’ve seen that for most solids, the solubility usually increases as temperature __________ We’ve seen that for most solids, the solubility usually increases as temperature __________ Does the same hold true for gases?? Does the same hold true for gases?? What does this graph tell us? What does this graph tell us? What type of relationship is shown between solubility and water temperature? What type of relationship is shown between solubility and water temperature? increases Temp ↑ Solubility ↓ Inverse

Gas Solubility As seen from the graph, as the water temperature __________ the gas solubility _________ As seen from the graph, as the water temperature __________ the gas solubility _________ Looking at the graph very closely… Looking at the graph very closely… Even at low temperatures, would you say that gases are VERY soluble? Even at low temperatures, would you say that gases are VERY soluble? decreases increases Most gases are far less soluble than many ionic solids

The Pressure’s ON!! Because most gases do not dissolve very well, solutions are put under high pressures to increase the gas solubility. Because most gases do not dissolve very well, solutions are put under high pressures to increase the gas solubility. For example…CO 2 from a high-pressure tank must be forced into the soda container just before it is sealed For example…CO 2 from a high-pressure tank must be forced into the soda container just before it is sealed This high pressure is quickly decreased when the container is opened This high pressure is quickly decreased when the container is opened The longer the beverage is open to the air, the more CO 2 escapes (“flat”) The longer the beverage is open to the air, the more CO 2 escapes (“flat”)

Factors Affecting Gas Solubility What relationship is shown in the graph? What relationship is shown in the graph? What type of relationship is this? What type of relationship is this? Based on what we’ve discussed, what factors would you say affect gas solubility? Based on what we’ve discussed, what factors would you say affect gas solubility?  Temperature  Nature of Solvent  Pressure Pressure ↑ Solubility ↑ Direct A linear graph with a positive slope = direct relationship

Affects on the Environment Oxygen dissolved in water is necessary for aquatic wildlife to survive. Oxygen dissolved in water is necessary for aquatic wildlife to survive. What if the temperature of the water increases? What if the temperature of the water increases? The amount of dissolved oxygen _______ The amount of dissolved oxygen _______ Also, as temperature increases, cold-blooded animals’ (fish) metabolism increases – they require more oxygen Also, as temperature increases, cold-blooded animals’ (fish) metabolism increases – they require more oxygen What causes water temperatures to increase? What causes water temperatures to increase?  summer heat, power plant cooling water, etc.

Can There Be Too Much O 2 ? YES!!! YES!!! When O 2 dissolves, so does N 2 (both in the air) When O 2 dissolves, so does N 2 (both in the air) Gas Bubble Trauma: bubbles form in the blood and tissues of fish Gas Bubble Trauma: bubbles form in the blood and tissues of fish O 2 can be used during metabolism O 2 can be used during metabolism N 2 bubbles block capillaries resulting in the death of the fish N 2 bubbles block capillaries resulting in the death of the fish

How Does it Happen? Supersaturation (110% to 124%) of O 2 and N 2 happens at the base of dams Supersaturation (110% to 124%) of O 2 and N 2 happens at the base of dams Released water forms “froth,” trapping large quantities of air Released water forms “froth,” trapping large quantities of air