Concentration and Solution Stoichiometry Solution homogenous mixture of 2 or more pure substances only one perceptible phase species do not react chemically Types of Solutions solid liquid gas Solutions The strong intermolecular forces of water also make it a good for the formation of aqueous solutions solid liquid gas alloy Ions in water Alcohol in water CO 2 in water Atmosphere Solutions are homogeneous mixtures of two or more pure substances. In a solution, the solute is dispersed uniformly throughout the. If the is water, the solution is said to be an aqueous solution. Solutions How Does a Solution Form? The intermolecular forces between solute and particles must be strong enough to overcome those that hold the solute particles together. Otherwise, the solute would be insoluble As a solution forms, the pulls solute particles apart and surrounds, or solvates, them.
How Does a Solution Form? Dissolving of solutes 1. Dissociation The breaking apart of ionic compounds into hydrated ions. (i.e. Salt in water) Electrolytes Substances that dissociate into ions when dissolved in water are called electrolytes. Soluble ionic compounds tend to be electrolytes. How Does a Solution Form? Dissolving of solutes 2. Dissolution The surrounding of particles by particles. (i.e. Sugar in water) Electrolytes and Nonelectrolytes A nonelectrolyte may dissolve in water, but it does not dissociate into ions when it does so. Molecular compounds tend to be nonelectrolytes, except for acids and bases. How Does a Solution Form? Dissolution (dissolving) of solutes 3. Ionization The breaking apart of covalent molecules into ions by interaction. (i.e. HCl gas in water) A strong electrolyte dissociates completely when dissolved in water. A weak electrolyte only dissociates partially when dissolved in water. Electrolytes
Strong Electrolytes Are Strong acids, Strong bases and Soluble ionic salts Miscible Degree to which a solute dissolves in a usually refers to liquid-liquid solutions vs. Immiscible Substances (liquid-liquid) that do not mix Solubility Generally reserved for the extent to which a solid or gaseous solute distributes in a liquid Concentration The concentration of a solution describes the amount of solute that is dissolved in a given quantity of. Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different. Concentrated vs. Dilute Concentrated relatively large amount of solute per unit of Dilute relatively small amount of solute per unit of Terms are NOT interchangeable with strong and weak solutions Common Expressions of Concentration Molarity (M) Percent by Volume (v/v) Percent by Mass (m/m) Molality (m) Normality (N) Parts per Trillion (ppt) Parts per Million (ppm) Parts per Billion (ppb) Ch. 13
Molarity Molarity (M) is one way to measure the concentration of a solution. Uses the number of solute particle in the units of moles and the volume of solution in the units of liters Molarity (M) = moles of solute volume of solution in liters 1. How many grams of Na 2 SO 4 are in 150. ml of 0.12 M Na 2 SO 4? Notice that the volume involved is the total volume of the resulting solution, not the volume of the alone. 2. Dissolve 5.00 g of NiCl 2 6 H 2 O in enough water to make 250 ml of solution. Calculate molarity. Preparing Solutions Weigh out a solid solute and dissolve in a given quantity of. Must add solute before filling to volume 1.0 L of water was used to make 1.0 L of solution. Notice the water left over.
Example: 3. Explain how to prepare 100 ml of a 0.150 M potassium permanganate solution. Not all solutes come as solids that can be massed. Some compounds, along with most acids, come as concentrated solutions that must be diluted. Dilution is the process of adding water to a more concentrated solution to make a solution of lower concentration. Dilution = the procedure for preparing a less concentrated solution from a more concentrated solution. Dilution watering down Simple ratio: M 1 V 1 = M 2 V 2 Dilution Add Solvent Moles of solute before dilution (i) M i V i = = Moles of solute after dilution (f) M f V f Dilution 5. Prepare 250 ml of 0.10 M HCl from concentrated HCl (12 M). Example: 4. How many milliliters of aqueous 2.00 M MgSO 4 solution must be diluted with water to prepare 100.0 ml of aqueous 0.400 M MgSO 4? 6.A student needs 125g Cl -. What volume of concentrated hydrochloric acid is needed to contain the required chlorine?
Solution Stoichiometry Just as the molar mass and Avagadro s # can be used to determine the number of moles for use in stoichiometric problems, so can the molarity be used to determine the number of moles given the volume of solution used. Map of Reaction Stoichiometry AX + BY AY + BX Rxn mole 1 mole 2 # of atoms or molecules Coefficients grams V gas givent&p M sol n given V 7. 750 ml of 6.00 M phosphoric acid reacts with 750 ml of 7.00 M calcium hydroxide. How many moles of excess reactant remains after the complete reaction? 8. Sodium metal reacts violently with water to form sodium hydroxide and hydrogen gas. If 10.0 g of Na reacts completely in 1.00 L of water, what is the molarity of the final solution?