Solutions and Acids and Bases

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Mixtures Homogeneous mixture: a uniform mixture of only one phase. Example: sugar in water, salt in water. Heterogeneous mixture: A mixture in which the particles of each component remain separate and can be observed as individual substances.

Solutions Solutions are homogeneous mixtures of substances with at least one solute and one solvent. Eg. Sugar in water. Liquid and gas state solutions are clear or transparent, and colourless or coloured

Solvent and Solute Solvent – The component of the solution present in greater amount. Solvent dissolves the solute Solute – The component of the solution present in lesser amount. The solute is dissolved by the solvent.

Classifying solutions PG. 192

Properties of Aqueous Solution An aqueous solution has water as the solvent – Symbol is (aq) Most solutions have water as the solvent therefore most solutions are aqueous. Solutions can be classified as electrolyte or nonelectrolyte – An aqueous solution can conduct electricity while a nonelectrolyte can not conduct electricity

Types of Electrolytes Salt: Metallic and non-metallic element NaCl and NaHCO 3 Acid: HCl (aq) -> H + (aq) + Cl - (aq) Base: NaOH (aq) -> Na + (aq) + OH - (aq)

Dissociation Ionic compounds dissolve into their component ions NaCl (s) -> NaCl (aq) -> Na + (aq) + Cl - (aq) PG 197

Dissociation examples a) Cu 2 CO 3 (aq)  ? b) (NH 4 ) 2 O (aq)  ? c) BaSO 4 (aq)  ? d) Ca(HCO 3 ) 2 (aq)  ? e) H 3 PO 4 (aq)  ? f) H 2 O (aq)  ?

Dissociation answers a) Cu 2 CO 3 (aq)  2 Cu + (aq) + CO 3 2- (aq) b) (NH 4 ) 2 O (aq)  2 NH 4 + (aq) + O 2- (aq) c) BaSO 4 (aq)  Ba 2+ (aq) + SO 4 2- (aq) d) Ca(HCO 3 ) 2 (aq)  Ca 2+ (aq) + 2HCO 3 - (aq) e) H 3 PO 4 (aq)  3H + (aq) + PO 4 3- (aq) f) H 2 O (aq)  H + (aq) + OH - (aq)

Homework Pg 195 – 1 a,b,e,f – 2 b, d, e

Acids and Bases PG 199

Energy Changes Chemical reactions can be exothermic or endothermic. What type of energy occurs when a substance is dissolved in water? – Energy absorbed when breaking bonds – Energy released when forming new bonds

Intermolecular forces What can you remember from intermolecular forces? – Dipole-dipole – Hydrogen bonding – London foces How do they effect dissolving? “Like dissolves like”

Substances in Water Some substances dissolve in water and some substances don’t; limestone vs sodium chloride Limit to the amount of substance can be added to water? – This is based on the solubility of the substance Prediction of precipitation reactions using a solubility chart

Strong or Weak Acid Strong acids are almost completely ionized in solution – Very conductive Weak acids, vary in conductivity

Molecular compounds Use solubility chart for ionic compounds but not an easy fix for molecules But can predict solubility in water based on IMF (polar liquid with hydrogen bonding) – Nonpolar compounds generally don’t dissvole – Polar compounds are slightly soluble – Polar compounds with hydrogen bonding are very soluble

Solution Concentration Since most solutions are colourless, the amount of substance within the solution is difficult to determine But can use the amount of the solute and the amount of solvent to find concentration Volume/volume mass/volume mass/mass

Parts per Million This is used for very small quantities Used when investigating concentration within drinking water

Amount Concentration This is the amount of solute dissolved into one litre of solution Can write this with [ ] to represent concentration Eg. [Cl - (aq) ] = 0.25 mol/L

Summary

Calculations Can use these concentrations to in calculation to determine the amount of a substance within a certain amount of solvent. Or anything with mass, volume and concentration

Concentrations of Ions Similar to calculations we have done before when looking at the amount of products and reactants is done with concentration HCl (aq) -> H + (aq) + Cl - (aq) 1 mol 1 mol 1 mol Example pg 211

Preparation of Solutions Two methods to prepare solutions – Dilution of a solution – Solid solute dissolved into a solution Juice from powder Pg 215

Standard solutions by Dilution Making fruit juice from concentrate Start with a stock solution and dilute to the desired concentration To calculate a new concentration, the amount of substance is the same (mass or number of moles) As the volume increases the concentration decreases Example pg 217

Uses in everyday life Needed for drugs or cough syrup Fruit juices Laundry detergent

Solubility Solutions are the best way to deal with various chemical reactions – Gases and solids are harder to control Three points to make solutions useful: – Handle the chemicals – Complete reactions – Controlled reactions

Solubility of solids When solids are added to a solution there is only a certain amount that will dissolved Once no more substance will dissolved have a saturated solution Has the units % W/V or mol/L similar to concentration Temperature can change that maximum level Remember the solute is dissolving into the solvent not reacting with the solvent

Solubility in Water Solids: increase solubility when the temperature is increased Gases: decrease in solubility when the T increases, also increase solubility at increased P Liquids: polar liquids have increased solubility with increase T; nonpolar liquids form layers with water (immiscible) and are insoluble; some polar molecules dissolve completely, miscible

Homework Pg 219: #4, 5, 6, 8

Solubility table