Solutions!

Classification of Matter Pure Substances Mixtures Homogeneous Heterogeneous Elements Compounds

Mixtures homogeneous: heterogeneous: will not separate small particles evenly distributed too small to be seen can’t be sorted or trapped by filter won’t scatter light settles upon standing variable particle sizes uneven distribution visibly different regions can be separated depending on particle sizes scatters light

Solution homogeneous mixture of 2 or more substances in a single physical state (phase)

Parts of a Solution solute = substance being dissolved solvent = dispersing medium substance being dissolved into

Can you identify the solute and solvent in each picture?

solute = ? solvent = ?

hints to identify solute & solvent substance that changes phase substance that have less of solvent: substance that maintains phase substance that have more of

Aqueous Solutions water is solvent transition metals form brightly colored solutions

solutions occur in all 3 phases solute solvent example gas air liquid water vapor in air solid SO2(s) in air - smog CO2(g) in water (soda) antifreeze(l) in water in car radiator salt water H2(g) in palladium metal dental amalagum fillings: Hg (l) in Au(s)/Ag(s) alloys: Brass, etc.

gas in a liquid: CO2 in and out of water bubbles mean it’s a mixture not a solution!

Concentration of Solutions

Concentration measurement that describes how much solute in given amount of solvent or solution express concentration using many, many different units pick the unit according to task at hand

Percent by mass OR by volume % = part x 100 whole

Twists in Word Problems sometimes ask for part or whole, not percent sometimes give volume/mass of solution sometimes give volume/mass of solvent and volume/mass of solute mass solution = mass solute + mass solvent

ppm (parts per million) used when solute is present in very small amounts (Regents board doesn’t quite follow this rule)

ppm (parts per million) ppm = grams solute x 1,000,000 ppm is ratio between mass solute & mass soln similar to % except the whole is 1,000,000 instead of 100 grams solution

About 0. 0043 g of O2 can be dissolved in 100 mL of water at 20oC About 0.0043 g of O2 can be dissolved in 100 mL of water at 20oC. Express in ppm. [memorize: 1 mL water has mass of 1 g] ppm = 0.0043g x 1,000,000 100.0043g = 43 ppm

CO2 gas has solubility of 0. 0972 g/100 g water at 40oC CO2 gas has solubility of 0.0972 g/100 g water at 40oC. Express in parts per million. ppm = 0.0972 g solute x 1,000,000 100.0972 g solution = 971 ppm

What is the concentration in ppm of a solution with 30.0 g NaNO3 in 70.0 g water? ppm = 30.0 g NaNO3 x 1,000,000 100.0 g solution = 300,000 = 3.0 X 105 ppm

How many grams of KOH are needed to be dissolved in water to make 2000 How many grams of KOH are needed to be dissolved in water to make 2000.0 grams of a 10.0 ppm solution? 10 ppm = ? grams KOH X 1,000,000 2000.0 g solution ? = 0.02 grams KOH