SolutionsBasic terminology

Students will be able to:1) understand the basic terminology

associated with solutions2) understand the methods used to measure

the concentration of solutions3) calculate the concentration of solutions

using 3 methods

Learning Goals

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

Success Criteria

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.

Solutions - Definition

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.

Solutions

In non-homogeneous mixtures – small particles diffract the light and cause the solution to glow.

Solutions are homogeneous and do not cause a glow.

The Tyndall Effect

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 solvent Example

Gas in gas Air (oxygen in nitrogen)

Gas in liquid Oxygen in water

Gas in solid Oxygen in ice

Liquid in gas Water in air (humidity

Liquid in liquid Alcohol in water

Liquid in solid Mercury in silver

Solid in liquid Salt water

Solid in solid All alloys (bronze – Sn in Cu), stainless steel

Classification of solutions

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 solutionBases release OH- ions into solution

Properties of Solutions

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

Solution Concentration

SaturationKinds of Saturation Definition

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.

Saturation

3 methods:1) Percentage Concentration2) Very Low Concentrations3) Molar Concentration

Measuring 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)

Percentage Concentrations

% V/V – volume per volume(liquid dissolved in liquid)

Determine the percentage composition (%V/V) of vinegar if 25 mL of acetic acid (HC2H3O2) 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 mL500x = 2500 5.0mL/100mL = 5.0% V/V acetic acid x = 5 mL (2 significant digits)

Percentage Concentration

% V/V – volume per volume(liquid dissolved in liquid)

Determine the amount of hydrogen peroxide (H2O2) 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 = 11.55 ⇨ 12 mL H2O2

Percentage Concentration

% 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 mL250x = 1250 5.0g/100mL = 5.00% W/V dextrose x = 5.0 g (3 significant digits)

Percentage Concentration

% 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 mL100x = (12.50)(750)100x = 9350 x = 93.5 g (3 significant digits)

Percentage Concentration

% 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 mL250x = 1250 5.0g/100mL = 5.00% W/V dextrose x = 5.0 g (3 significant digits)

Percentage Concentration

Usually found in environmental measurements – levels of a contaminant found in water or air.

1ppm (part per million) (1:1000000 ratio) 1ppb (part per billion) (1:1000000000 ratio)

1ppm = 1 g/106 mL 1ppm = 1g/1000L 1ppm = 1 mg/L 1ppm = 1mg/kg 1ppm = 1μg/g

Very Low Concentrations

Molar concentration = number of moles (solute)

volume of solution

C = n n= m C = mV m = CMV V M M

Molar Concentration