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Solutions

Solutions. A. Definitions. Solute - substance being dissolved. Solution – a mixture of substances that has uniform composition (homogenous mixture). Solvent – substance that is doing the dissolving (usually present in greater amounts). Solutions: Basic Definitions.

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Solutions

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  1. Solutions

  2. A. Definitions Solute - substance being dissolved Solution – a mixture of substances that has uniform composition (homogenous mixture) Solvent – substance that is doing the dissolving (usually present in greater amounts)

  3. Solutions: Basic Definitions • Soluble – when a substance will dissolve in another substance • Ex: salt and water • Insoluble – when a substance will not dissolve in another substance • Ex: sand & water

  4. Solutions: Basic Definitions • Miscible – when two liquids are soluble in each other • Ex: alcohol & water • Immiscible – when two liquids are not soluble in each other • Ex: oil & water • Aqueous – a solid dissolved in water

  5. Solutions: Basic Definitions • Electrolyte – a solution that separates into charged particles that conducts an electric current • Non electrolyte – solution that separates into charged particles that does not conduct an electric current

  6. NONPOLAR NONPOLAR POLAR POLAR Solvation “Like Dissolves Like”

  7. PoLaR vS. nOnPoLaR? Molecules may be polar or non‐polar depending on the types of bonds and the arrangement of the bonds, that is, the shape of the molecule. • In general: • Polar – unequal distribution of electrons • Ionic Compounds = Polar • EX: Water is the universal solvent for polar compounds • Nonpolar – equal distribution of electrons • Covalent Compounds = Nonpolar ***Remember the phrase “LIKE DISSOLVES LIKE”

  8. Increasing the Rate of Solution Agitation • If you increase the speed of the particles, you increase the dissolving process Increasing Temperature • As you increase the temperature, more particles will collide (high KE), thus increasing the rate of reaction Increasing Surface Area • Smaller particles dissolve faster than larger particles due to an increased surface area Which will dissolve faster: Sugar cube vs. Teaspoon of sugar?

  9. Solubility • Solubility • Maximum grams of solute that will dissolve in 100 g of solvent at a given temperature • Varies with temperature • Based on a saturated solution

  10. UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form Solubility concentration

  11. Solutions: Basic Definitions • unsaturated solution - If the amount of solute dissolved is less than the maximum that could be dissolved (point belowthe line) • saturated solution - solution which holds the maximum amount of solute per amount of the solution under the given conditions (point on the line) • supersaturated solution - solutions that contain more solute than the usual maximum amount and are unstable(pointabove the line) Which solution allows for more solute to be added?

  12. Solubility Graph • Solubility Curve • Shows the dependence of solubility on temperature • Factors that affect a substance’s solubility: • Amount of solute (in grams) • Amount of solvent (in grams) • Specified temperature (in °C)

  13. KNO3 KCl NaCl To read the graph: Look for the given information first. Read up or over until you hit the linefor your compound. Go to the other axisfor the information you are looking for. Exa: How many grams of KNO3 will dissolve in 100 g of H2O at 50C? _______ g Exb: At what temperature will 52 grams of KCldissolve in 100 g of H2O? _______ C Exc: What kind of solution would you have if you dissolved 10 g of KCl in 100 g H2O of at 0  C? Unsaturated 79 • 81

  14. KNO3 KCl NaCl Calculating from the Graph • Sometimes a question can be asked that cannot be answered solely from reading the graph. But information can be obtained from the graph to help answer the question. • Find the maximum amount of NaCl that will dissolve at the given temperature. • Subtract the given amount from the maximum amount. • Exa: Dissolving 25 g of NaCl in 100 g of H2O at 75 °C produces an unsaturatedsolution. How many more grams of NaCl must be added to saturate the solution? • 40 g – 25 g = 15 g needed

  15. KNO3 KCl NaCl • Exb: What is the minimum mass (in grams) of 90 °C water needed to dissolve 70 grams of KCl? • Find the maximum amount of KCl that will dissolve at the given temp. ______ g • Set up an inequality that shows the info you have at that temp • on the left, write what you see on the graph • on the right, write what you want to do. • Cross multiply to solve for X 55 55 g KCl = 100 g H2O 70 g KCl X g H2O

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