SOLUTION STOICHIOMETRY Part 1a Unit 2 Chapter 4 1

Solutions  A solution is homogenous mixture of 2 or more pure substances  Solvent: most abundant substance in a solution (water is the universal solvent because of strong polar bonds and bent shape)  Solute: all other substances present

Water Called the “universal solvent” Bent shape (angle = 105) O – H bonds are polar covalent resulting from the more electronegative O atom attracting the electrons toward itself The O is partially negative while the H’s are partially positive

Dissociation When an ionic substance dissolves in water, the solvent pulls the individual ions from the crystal and solvates them. This process is called dissociation.

Dissociation An electrolyte is a substances that dissociates into ions when dissolved in water and produces a solution that can conduct electricity.

Electrolytes A nonelectrolyte may dissolve in water, but it does not dissociate into ions when it does so.

Electrolytes and Nonelectrolytes Soluble ionic compounds tend to be electrolytes.

Electrolytes and Nonelectrolytes Molecular compounds tend to be nonelectrolytes, except for acids and bases.

Electrolytes A strong electrolyte dissociates completely when dissolved in water. A weak electrolyte only dissociates partially when dissolved in water.

Strong Electrolytes Are… HCl H + + Cl – 100 molecules of HCl yields ? Strong acids Strong bases

Strong Electrolytes Are… Strong acids Strong bases Soluble ionic salts

Molarity Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different. Molarity is one way to measure the concentration of a solution. moles of solute volume of solution in liters Molarity (M) =

Molarity Example 1: a chemist makes a 400 mL solution by adding 67.4 g of AgNO 3 to some water. What is the molarity of this solution? –S–Step 1 – convert from grams to moles

Example 1: a chemist makes a 400 mL solution by adding 67.4 g of AgNO 3 to some water. What is the molarity of this solution? –Step 2 – calculate molarity

Molarity Example 2: how many moles of a solute are present in 34 mL of 3.64 M Ba(OH) 2 ?

Molarity Calculate the molarity of a solution by dissolving 11.5 grams of solid NaOH in enough water to make 1500 mL of solution. Give the concentration of each type of ion in the following solutionsl: –0.5 M Co(NO 3 ) 2 –1.0 M Fe(ClO 4 ) 3 Typical blood serum is about 0.14 M NaCl. What volume of blood contains 1.0 mg NaCl?

Mixing a Solution To create a solution of a known molarity, one weighs out a known mass (and, therefore, number of moles) of the solute. The solute is added to a volumetric flask, and solvent is added to the line on the neck of the flask.

How would you do this? How would I make 1.00 L of an aqueous M K 2 Cr 2 O 7 solution –1. –2. –3. –4.

Dilution of stock solutions One can also dilute a more concentrated solution by –Using a pipet to deliver a volume of the solution to a new volumetric flask, and –Adding solvent to the line on the neck of the new flask.

Dilution The molarity of the new solution can be determined from the equation M c  V c = M d  V d, where M c and M d are the molarity of the concentrated and dilute solutions, respectively, and V c and V d are the volumes of the two solutions.

Making Dilutions Example: Suzie needs 3L of a 0.05M HCl. She only has 12M HCl available. How much does she need to dilute to make her solution?

How would you do this? How would I prepare 500 mL of 1.00 M acetic acid from a 17.4 M solution –1. –2. –3. –4.

Classifying Chemical Reactions SynthesisSynthesis DecompositionDecomposition Single replacementSingle replacement Double ReplacementDouble Replacement CombustionCombustion

Synthesis Two or more substances react to form ONE productTwo or more substances react to form ONE product A + B  AB

Synthesis Reaction of two elementsReaction of two elements ___ Al + ___ Cl 2  ___ AlCl 3 Al 3+ Cl

Reaction of two compoundsReaction of two compounds Reaction of element and compoundReaction of element and compound Synthesis CaO + H 2 O  Ca(OH) 2 SO 2 + O 2  SO 322

Decomposition One substance breaks down into two or more simpler productsOne substance breaks down into two or more simpler products AB  A + B

Decomposition __ NaN 3 (s)  ___ Na (s)+ ___ N 2 (g) 223 __ CaO (s)  ___ Ca (s)+ ___ O 2 (g) 22

Single Replacement Reactions One element replaces another element in a compound to form a new compound and elementOne element replaces another element in a compound to form a new compound and element A + BX  AX + B

Reactivity Series MetalsMetals A more reactive metal will replace a less reactive metal in a solutionA more reactive metal will replace a less reactive metal in a solution Li K Ca Na Mg Al Mn Zn Fe Ni Sn Pb Cu Ag Au most active least active

examples aluminum + iron (III) oxidealuminum + iron (III) oxide Al Fe 2 O 3 + More reactive? Al 3+ O 2- Al 2 O 3 Fe + Fe 3 + O

examples silver + copper (I) nitratesilver + copper (I) nitrate Ag CuNO 3 + More reactive? Cu 1 + NO 3 1- NO RXN

Double Replacement Exchange of cations between two ionic compoundsExchange of cations between two ionic compounds A B + C D  AD + CB switch

Will the Solutions React? One of the following things must occur for a reaction to occur:One of the following things must occur for a reaction to occur: –Precipitate is produced [(s) or (  )] –Gas is evolved [(g) or (  )] –Water is made [(l) or (g)] Use the solubility table to determine if a solid is madeUse the solubility table to determine if a solid is made

Example Problem Lithium iodide and aqueous silver nitrate reactLithium iodide and aqueous silver nitrate react Li 1+ I 1- Ag 1+ NO 3 1- Li I AgNO 3 LiNO 3 Ag I + + (aq) Use a solubility table to determine state of each component. (aq)(s) (aq)

Combustion Compound reacts with O 2Compound reacts with O 2 Hydrocarbon – compound with only carbon and hydrogenHydrocarbon – compound with only carbon and hydrogen

Combustion Combustion of hydrocarbons ALWAYS produces CO2 and H2O C x H y + O 2 CO 2 + H 2 O

Example Problem Show combustion of propane (C 3 H 8 ) gasShow combustion of propane (C 3 H 8 ) gas C3H8C3H8 O2O2 CO 2 H2OH2O++534