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Solutions

Solutions. By: Cash Li. What is a solution?. A solution is a homogeneous mixture of two or more substances on a single physical state. In a solution, the solute is dispersed uniformly throughout the solvent. How it form?. Solvent molecules attracted to surface ions.

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Solutions

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  1. Solutions By: Cash Li

  2. What is a solution? • A solution is a homogeneous mixture of two or more substances on a single physical state. • In a solution, the solute is dispersed uniformly throughout the solvent.

  3. How it form? • Solvent molecules attracted to surface ions. • Each ion is surrounded by solvent molecules. • Enthalpy (DH) changes with each interaction broken or formed.

  4. Properties of a solution • The particles in a solution are very small • The particles in a solution are evenly distributed or intermingled uniformly on a molecular level. • The particles in a solution will not separate no matter how long the solution is allowed to stand under constant conditions

  5. Solute v. Solvent • A solute is the substance that dissolves • In a lemonade the sugar is a solute • Solvent is the substance that does the dissolving • Water is a solvent and it is known as the universal solvent

  6. Soluble • A substance that dissolves in another substance is said to be soluble. • Also a substance is soluble also means that it is capable of being dissolved.

  7. Factors affecting solubility • The stronger the intermolecular attractions between solute and solvent, the more likely the solute will dissolve. • like dissolves like: • Polar substances tend to dissolve in polar solvents. • Nonpolar substances tend to dissolve in nonpolar solvents

  8. Solubility Curve

  9. Solubility Curve Cont. • The solubility curve is the most helpful tool in the reference table that will find the saturation, and solubility of the given substances. • How to use the curve: • The line of each substances show their soluble points or their saturation points. • If number falls above the line then it is super saturated and there will be precipitants. • If the number falls below the line then it is unsaturated and no precipitants will fall.

  10. Types of Solution • Solid Solution • They are formed by melting the component metals, mixing them together and then allowing them to cool • Gas • If the solvent is a gas, only gases are dissolved under a given set of conditions. An example of a gaseous solution is air (oxygen and other gases dissolved in nitrogen). Since interactions between molecules play almost no role, dilute gases form rather trivial solutions. In part of the literature, they are not even classified as solutions, but addressed as mixtures.

  11. Types of Solution cont. • Liquid • Miscible • This means that the liquids of two different substances mix well together. • Immiscible • Two different substances will no mix well together. • Ex: water and oil • Aqueous • An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending (aq) to the relevant formula, such as NaCl (aq). The word aqueous means pertaining to, related to, similar to, or dissolved in water.

  12. Concentration of Solutions • The concentration of a solution is the amount of solute in a given amount of solvent or solution • Concentration • Molarity • Molality

  13. Molarity • The number of moles of solute dissolved on each liter of solution. • Equation • M = m/L • Also volume is temperature dependent, so molarity can change with temperature change.

  14. Molality • The number of moles of solute dissolved in each kilogram of solvent • Equation • Molality = mole of solute/ kilogram of solvent

  15. Mole Fraction • Equation • Mole fraction = moles of components/total moles of solution • In some applications, one needs the mole fraction of solvent, not solute—make sure you find the quantity you need!

  16. Saturation • Saturated solution • Solvent holds as much solute as is possible at that temperature. • Undissolved solid remains in flask. • Dissolved solute is in dynamic equilibrium with solid solute particles

  17. Saturation cont. • Unsaturated Solution • Less than the maximum amount of solute for that temperature is dissolved in the solvent. • No solid remains in flask.

  18. Saturation cont. • Supersaturated • Solvent holds more solute than is normally possible at that temperature. • These solutions are unstable; crystallization can often be stimulated by adding a “seed crystal” or scratching the side of the flask.

  19. Finished

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