Basic terminology

Students will be able to: 1) understand the basic terminology associated with solutions 2) understand the methods used to measure the concentration of solutions 3) calculate the concentration of solutions using 3 methods

 Students will be able to: 1) apply correct terminology in their discussions in Solution Chemistry. 2) calculate percentage concentration, very low concentrations (in ppm) and molar concentrations

 Solutions are homogeneous mixtures of substances in which at least one (and often more) solute is dissolved into one solvent.  Aqueous solutions are the most common since water is the most common solvent.  Homogeneous mixture = uniform mixture in which the two substances are indistinguishable.

 Typically, we think of solutions in which a solid is dissolved into a liquid. This is not always the case – on the next slide we will discuss other types of solutions.  Aqueous solutions, or solutions in which the solutes are dissolved in water, are always transparent and may be coloured or colourless.  In some mixtures, like milk, small non-dissolved particles scatter light and make them transparent or opaque. Milk is not a solution but a suspension in which small particles (milk fats) are suspended in water.

 In non-homogeneous mixtures – small particles diffract the light and cause the solution to glow.  Solutions are homogeneous and do not cause a glow. Faraday Tyndall effect in our Daily life : 1)Light beams from headlights of cars and motor vehicles on a dusty road. 2)Illumination of light beam from film projector in smoke filled theater's

Solute in solventExample Gas in gasAir (oxygen in nitrogen) Gas in liquidOxygen in water Gas in solidOxygen in ice Liquid in gasWater in air (humidity Liquid in liquidAlcohol in water Liquid in solidMercury in silver Solid in liquidSalt water Solid in solidAll alloys (bronze – Sn in Cu), stainless steel

1) Electrolytes – conduct electricity These are polar compounds dissolved in other polar compounds. ex. Salt water, acids, bases 2) Non-electrolytes – non-conductive These are polar compounds dissolved in other polar compounds. ex. Motor oil 3)Acids and Bases Acids – release H + ions into solution Bases release OH - ions into solution

 Concentration – a measure of the ratio of solute to the total volume of the solution.  Dilute – relatively small quantity of solute per unit volume of solution  Concentrated – relatively large quantity of solute per unit volume of solution

Kinds of SaturationDefinition Saturated Solution A solution with solute that dissolves until it is unable to dissolve anymore, leaving the undissolved substances at the bottom. Unsaturated Solution A solution (with less solute than the saturated solution) that completely dissolves, leaving no remaining substances. Supersaturated Solution A solution (with more solute than the saturated solution) that contains more undissolved solute than the saturated solution because of its tendency to crystallize and precipitate.

3 methods: 1) Percentage Concentration 2) Very Low Concentrations 3) Molar Concentration

 % V/V – volume per volume (liquid dissolved in liquid) Found in stores – easy for the consumer to understand (ex. Vinegar, hydrogen peroxide, rubbing alcohol)  % W/V - weight per volume (solid dissolved in liquid) Often seen in medical solutions (ex. Salt, blood solutions in IV bags)  % W/W - weight per weight (solid dissolved in solid) Often seen in alloys, especially jewelry. (ex sterling silver, gold, bronze)

 % V/V – volume per volume (liquid dissolved in liquid) Determine the percentage composition (%V/V) of vinegar if 25 mL of acetic acid (HC 2 H 3 O 2 ) is dissolved into 500 mL of solution. Approach – convert to mL per 100 mL (remember % is expressed as a value out of 100) 25 mL = x cross-multiply! 500 mL 100 mL 500x = mL/100mL = 5.0% V/V acetic acid x = 5 mL(2 significant digits)

 % V/V – volume per volume (liquid dissolved in liquid) Determine the amount of hydrogen peroxide (H 2 O 2 ) in a 330 mL bottle of 3.5% solution. Approach – convert from a percentage (mL per 100 mL) to a value out of 330 mL. 3.5% = 3.5 mL = x cross-multiply! 100 mL 330 mL 100x = (330mL)(3.5mL) 100x = 1155 mL x = ⇨ 12 mL H 2 O 2

 % W/V – weight per volume (solid dissolved in liquid) A D5W intraveinous (IV) bag contains 12.5 g of dextrose dissolved into 250 mL of solution. What is its percentage concentration? Approach – convert to g per 100 mL (remember % is expressed as a value out of 100) 12.5 g = x cross-multiply! 250 mL 100 mL 250x = g/100mL = 5.00% W/V dextrose x = 5.0 g (3 significant digits)

 % W/V – weight per volume (solid dissolved in liquid) How much salt needs to be dissolved in 750 mL of water to make a 12.5% W/V solution? Approach – convert from g per 100 mL to a volume of 750 mL 12.5 g = x cross-multiply! 100 mL 750 mL 100x = (12.50)(750) 100x = 9350 x = 93.5 g(3 significant digits)

 % W/W – volume per volume (solid dissolved in solid) Since fine silver (99.9% W/W) is too soft for working into silverware or jewelry, most silverware is made from sterling silver. What is its percentage concentration of a silver platter that contains 236g of silver and has a total mass of 255g? Approach – convert to g per 100 mL (remember % is expressed as a value out of 100) 12.5 g = x cross-multiply! 250 mL 100 mL 250x = g/100mL = 5.00% W/V dextrose x = 5.0 g (3 significant digits)

 Usually found in environmental measurements – levels of a contaminant found in water or air.  1ppm (part per million) (1: ratio)  1ppb (part per billion) (1: ratio)  1ppm = 1 g/10 6 mL  1ppm = 1g/1000L  1ppm = 1 mg/L  1ppm = 1mg/kg  1ppm = 1μg/g

 Molar concentration = number of moles (solute) volume of solution C = nn= mC = mVm = CMV V M M