Solutions

Solutions homogeneous mixtures in which one substance is dissolved into another the “solute” dissolves in the “solvent” example: Kool-Aid - water is the solvent, the drink mix is the solute

A few other terms... Solvation Hydration When solute particles are surrounded by solvent molecules Hydration The name of the solvation process when the solvent is water

Solubility a measure of the amount of a substance that will dissolve depends upon the solvent used amount of solvent temperature

Temperature effects solid solute/liquid solvent: usually, increase in temperature means an increase in solubility ex: sugar in hot vs. cold water gas solute/liquid solvent: usually, increase in temperature means a decrease in solubility warm pop goes flat faster

Rate of Solution describes how fast a solute dissolves in a given solvent depends on: temperature stirring/agitation particle size

Colligative properties of Solutions -properties of solutions that are affected by the number of dissolved particles, not the identity of the particles Example: vapor pressure lowering The more particles (with little tendency to vaporize) that are added to a solvent, the lower the vapor pressure of the solution becomes

Colligative properties of Solutions Boiling point elevation: The presence of dissolved particles tends to increase the boiling point of a liquid The more dissolved particles, the greater the effect Ocean water would require a higher temperature to boil at than pure water

Colligative properties of Solutions Freezing point depression The presence of dissolved particles tends to lower the freezing point of a liquid Salt or other substances are used to melt ice, because as they dissolve into the ice, they lower the freezing point of the ice, and thus even more of the ice melts

The “state” of a solution A solution is described as: unsaturated saturated supersaturated And as: concentrated dilute

Unsaturated the condition in which more solute could be dissolved into the solvent contains less dissolved solute than a saturated solution

Saturated all the solute that can dissolve in the given amount of solvent at that temperature has been dissolved if the temperature or amount of solvent changes, the solution may not remain saturated

Supersaturated an unstable condition where more solute is dissolved in a given amount of solvent that should be able to be dissolved prepared by slowly cooling a hot saturated solution

For a given amount, which type of solution contains the LEAST amount of solute? A. solvated B. saturated C. supersaturated D. unsaturated

Concentrated In a concentrated solution, the amount of solute is large compared to the amount of solvent it is dissolved in Ex: juices, detergents

Dilute In a dilute solution, there is much more solvent than solute Solutions are “diluted” by adding more solvent

A solution can be... concentrated and saturated concentrated and unsaturated dilute and saturated dilute and unsaturated

Solutions

A few other terms... two liquids that dissolve into each other are said to be miscible; two that don’t are immiscible water and oil are immiscible an insoluble solid is one that does not appreciably dissolve in a given solvent CaCO3 is insoluble in water

Quantify it... The problem is: just how much is “a lot” or “a little”? We must find a way to quantify the concentration of a solution There are various ways to do this

Quantify it... Percent solution volume of solute/volume of solvent mass of solute/mass of solvent Not directly useful for us - chemists usually work in “moles”

Molarity Molarity of a solution is equal to the number of moles of solute divided by the number of liters of solution M = mol/L The larger the molarity, the more concentrated the solution

Solutions