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Solutions & Molarity. What are solutions?. Homogeneous mixtures Can be solid, liquid or gas Aqueous solution Water that contains dissolved substances. Parts of a Solution. Solvent. Solute. The dissolving medium Water Gasoline
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What are solutions? • Homogeneous mixtures • Can be solid, liquid or gas • Aqueous solution • Water that contains dissolved substances
Parts of a Solution Solvent Solute • The dissolving medium • Water • Gasoline • Non-polar molecules will dissolve in other non-polar molecules! • Dissolved particles • Salt, sugar • Oil, grease • Remember: only the surface area of a solute can be dissolved!
Creating a (water) Solution • Water is in constant motion (kinetic energy) • water molecules collide with solute molecules • Water is polar • It is slightly + & - • Attracted to ions • SOLVATION – water surrounds each charged ion
Factors of Dissolving Time • Stirring (agitation) • ↑ time b/c fresh solvent is brought in contact with the solute • Only affects rate, not amt of solute that will dissolve • Temperature • ↑ temp ↑ time b/c it increases the kinetic energy of the solvent, which causes more collisions with the solute. • Surface Area • ↑ surface area ↑ time b/c more solute is exposed to the solvent
Solubility • The amt of solute that dissolves in a given amt of solvent at a specific temp & pressure to make a saturated solution (g solute/100g solvent) • contains the max amt of solute! • If more solute is added it will NOT dissolve Unsaturated – doesn’t have all the solute that it can dissolve
Factors Affecting Solubility TEmperature Pressure • Affects solids, liquids & gas • Usually solubility ↑ as the temp ↑ • Affects gases the most! • Solubility ↑ as pressure ↑ • HENRY’S LAW • Solubility (S) is directly proportional to the pressure (P) • S1 = P1 S2 P2
Molarity (M) • Number of moles of a solute dissolved in 1 liter of solution • Dilute – small amt of solute • Concentrated – large amt of solute
Molarity Example IV saline solutions contain 0.90g NaCl in 100mL of solution. What is the molarity?
Dilutions • Reduces the number of moles of solute per unit volume • The total # of moles doesn’t change! • M1V1 = M2V2
Dilution Example How many milliliters of aqueous 2.0M MgSO4 solution must be diluted with water to prepare 100mL of aqueous 0.40M MgSO4?