Properties of Solutions

Solutions Solutions are homogeneous mixtures of two or more pure substances. In a solution, the solute is dispersed uniformly throughout the solvent.

Salt is stirred into water

Solute- the substance that is being dissolved- usually present in smaller amount Solvent-the substance that dissolves the solute and is found in larger amount Water is the universal Solvent!!! Water solutions are called aqueous solutions

Solutions are homogeneous mixtures Are clear and do not disperse light Can have color (but are transparent) Will not settle on standing Will pass through a filter

Dirt in Water A suspended mixture of particles of this type is called a colloid, or colloidal suspension, or colloidal dispersion

A solution is said to be dilute if there is less of the solute. A solution is said to be concentrated if it has more solute. Higher temps dissolve more solids into liquids Lower temp liquids dissolve more gas

A solid can be dissolved in another solid. When metals are mixed to form a solution, the result is called an alloy. Air is an example of a mixture of gases forming a solution. Its not just liquid/liquid or solid in liquid.

Solubility Is defined as the mass of solute which can be dissolved in 100 grams of solvent at a specific temperature. Most common solvent= water Solubility curve is a graph showing the concentration of a substance as saturated, unsaturated or supersaturated as a function of temp

Saturated- solution which contains all the solute that can be dissolved under specific temperatures. Unsaturated- solution which could have more solute dissolved into it Supersaturated- solution can be “tricked” into containing more solute than normal by warming solvent and than slowly cooling the solution

Solubility curve Saturated Unsaturated Supersaturated

Solubility curve Any point on a line represents a saturated solution. In a saturated solution, the solvent contains the maximum amount of solute. Example At 90 o C, 40 g of NaCl(s) in 100g H 2 O(l) represent a saturated solution.

Solubility curve Any point above a line represents a supersaturated solution. In a supersaturated solution, the solvent contains more than the maximum amount of solute. A supersaturated solution is very unstable and the amount in excess can precipitate or crystallize. Example At 90 o C, 50 g of NaCl(s) in 100g H 2 O(l) represent a supersaturated solution. Eventually, 10 g of NaCl(s) will precipitate.

Solubility curve Any solution can be made saturated, unsaturated, or supersaturated by changing the temperature.

At 40C 15gt of KCLO3 will dissolve in 100g of water At 40C 30 g of KCLO3 will dissolve in 200g of water At 40C 7.5g of KCLO3 will dissolve in 50g of water.

Factors affecting Solubility Temperature: Liquid/Solid- Higher temps dissolve more Gas- Low temp dissolves more Pressure: As pressure increases the solubility of gasses in liquids increases. Has no affect on liquids or solids

Like Dissolves Like!!! Solute type Nonpolar Polar Solvent Solvent Nonpolar Soluble Insoluble Polar insoluble soluble Ionic Insoluble soluble Example: H20, CO2, NH3

Soluble: All of those ions can dissolve in H2O Exceptions- these ions are insoluble Insoluble: All ions cannot dissolve in water Exceptions: These ions cause them to be soluble.

Every time a group 1 ion is present, it’s soluble Na, K, Rb, Cs, Fr, NH4 You use the – ion to judge solubility AgNO3 All nitrates are soluble FeCO3 insoluble CO3 are insoluble Fe is not an exception. PbSO4 insoluble because Pb is an exception NaBrO3 soluble because Na is group 1 ion

Concentrations of Solutions Because solutions are homogenous mixtures, their compositions can vary That’s why we call them dilute or concentrated, but these terms are not precise Today we will talk about how to find the exact amount of solute within a solution

To solve the following use table T in your reference tables. Make sure to always write down your unknowns. You might have to convert grams to moles for Molarity questions by finding the amu of a compound (add up weights of atoms) that is also your gram formula mass. Than use mole equation to convert.

Molarity What is the molarity of a solution that contains 4.0 mol of NaOH in 0.50L of solution? What is the molarity of a solution containing 82.0g of Ca(NO3)2 in 2.0 L of solution?

Percent by mass What is the percent mass of sodium hydroxide 2.50g of NaOH are added to 50.00g of H20?

Percent by Volume What is the percent by volume of alcohol if 50.0 mL of ethanol is diluted with water to form a total volume of 300mL?

Parts per Million Approximately g of oxygen can be dissolved in 100mL of water at 20C. Express this in terms of parts per million?