Solutions Concentration, Molarity, Polarity and Solution Stoichiometry

What is a Solution? A liquid mixture of 2 or more solutes in a solvent. Solute – that which is dissolved Solvent – the agent that does the dissolving Solutes are dissolved INTO solvents SO… How do we tell how much solute is in a solvent? Is it the same amount every time? Is there a maximum amount? Does it matter how much solute is in there when considering reactions?

Any Solute? If I drop a penny in a beaker of water, will it dissolve? Make a list of things you know WILL dissolve in water and a list of things that you know WILL NOT dissolve in water. What is the difference?

LIKE DISSOLVE LIKE Polar: - Unequal sharing of electrons - Ionic bonding/ions - Polar dissolves Polar Non-Polar: - Equal Sharing - Equal Pulling (tug of war) - Often Covalent - Non-polar dissolves non-polar

Electronegativity How hard an ion will hold on to it’s electrons… basically.

Dissociation or not? Dissociation is dependant on two forces Intramolecular – forces within a molecule Intermolecular – forces between 2 or more molecules Ionic – dissociates into parent ions Covalent/Molecular – usually does not dissociate, rather the polar “ends” will attract to other dipoles or the non-polar will attract to other non-polar.

Ionic vs. Covalent (Molecular) MORE when we get to bonding and drawing molecules!

Concentration Once we’ve figured out that something CAN dissolve (qualitative), how do we quantify how much of that substance can be dissolved (quantitative)? Answer: Concentration – the amount of solute per unit of solvent Usually in: (moles solute)/(liter of solution) Aka: MOLARITY So… get solute to moles, get solution to L Then you have your concentration

Factors that effect Concentration Amount of solute Amount of solvent/solution total Solubility – how well something will dissolve Structure Ionization Temperature Pressure Surface area SEE SOLUBILITY RULES SHEET EXAMPLES…

Solubility and Temp General Trend: As temperature rises, so does solubility

Calculating Concentrations 1) Given 2.6 moles of NaCl in a 2L solution, what is the concentration of NaCl? 2) Mr. Rupp mixed 25g of solid hydrochloric acid in 1000ml of water. What is the concentration of the acid? 3) 25 mL of 18M H 2 SO 4 is diluted with 975 mL of water. What is the final concentration? 4) 25 mL of 18M H 2 SO 4 is diluted to a final concentration of.1M. What is the final volume of the solution?

Solution Stoich! Solution stoich follows the same rules as the stoichiometry we have been doing. Start with what you are given Get to moles Mole to mole ratio Get it to what you need The only change is this time you won’t be starting with masses, you’ll be starting with volumes and/or concentrations! Don’t worry about the solvent in the reaction or the calculations… usually.

Solution Stoich Problems 1) James adds an excess of Zn metal to.25 L of sulfuric acid with a concentration of 5M. How much hydrogen is produced?

Solution E/L 1) Ensley reacts 25g of Zn with.5L of 18M sulfuric acid. A) How much hydrogen is produced? B) How much of the excess reactant is left over?

Other ways to show concentration Molality – (moles solute)/(kg solvent) Mass Percent – (g solute)/(g solution) x100 Percent by volume – (L solute)/(L solution) x100