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UofL CHEM 101 - Solutions
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Chem 101 1st Edition Lecture 5Outline of Last Lecture II. Avogadro’s NumberIII. StoichiometryIV. Lewis Dot StructureV. VESPR Outline of Current Lecture VI. SolutionsA. Aqueous solutionsVII. Properties of SolutionsVIII.Concentration calculationsIX. MolarityCurrent LectureII. Solutions: a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent).a. Solute: This is the minor component of the solutionb. Solvent: the liquid that dissolves the chemical compoundc. Aqueous solution: water based solution. Water is the solvent. Water is considered the universal solvent because it reacts with lots of compounds.d. Disassociation: the disconnection or separation of something from something else or the state of being disconnected.i. Dissociation of NaClNaCl(aq) Na+(aq) + Cl- (aq)The subscript (aq) = aqueous (l)= liquid(s)= solidThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. Properties of Solutionsa. Electrolyte: a liquid or gel that contains ions and can be decomposed by electrolysis, e.g., that present in a battery. All compounds that disassociate into ions in water. (“charged”)b. Non-electrolyte: a substance that does not readily ionize when dissolved or melted and is a poor conductor of electricity. Nonionic compounds such as sugarand ethanol (“no charge”)i. There are strong and weak electrolytes ii. If a nonelectrolyte is dissolved in water, ions do not form and electricity will not pass through the light bulb. iii. Charges indicate electrolytes (anions and cations) Example: non-electrolyte: pure water: H-O-H (no charge molecule) What about NaCl? Na + and Cl- (-1 / +1) = neutral: no chargeWhich of the following compounds are electrolytes?[a] C4H10 (this is a covalent compound that doesn’t form ions)[b] SO2 (this is a covalent compound that doesn’t form ions) [c] KCl (is an ionic compound)[a. nonelectrolyte] [b. nonelectrolyte] [c. electrolyte]c. Precipitate: Precipitation reactions occur when cations and anions in aqueous solution combine to form an insoluble ionic solid called a precipitate. cause (a substance) to be deposited in solid form from a solution.i. Professor Franco will provide a list of solubility when necessary, if the compound is not on the list assume it is soluble or aqueous. d. This is an undissociated reaction/ undissociated equation: Pb+2(aq)(NO3)2 (aq) + KI(aq)Pb+2(aq) + NO3-(aq) + K+(aq) + I-(aq)  K+(aq) + NO3-(aq) + PbI2(s)e. Total ionic equation: the complete ionic equation is used to describe the chemical reaction while also clearly indicating which of the reactants and/or products exist primarily as ions in aqueous solution. i. Start with a balanced molecular equation. f. Spectator ions: is an ion that does not actively form a new compound in a chemical equation. i. They can be canceled out to produce the net ionic equationg. Net ionic equation: are equations that show only the soluble, strong electrolytesreacting (these are represented as ions) and omit the spectator ions, which go through the reaction unchanged.h. How do you know if your equation is a precipitate?i. The determining factors of the formation of a precipitate can vary. 1. Some reactions depend on temperature, such as solutions used for buffers, whereas others are dependent only on solution concentration. 2. The solids produced in precipitate reactions are crystalline solids, and can be suspended throughout the liquid or fall to the bottom of the solution. 3. The remaining fluid is called supernatant liquid. 4. The two components of the mixture (precipitate and supernate) can be separated by various methods, such as filtration, centrifuging, or decanting.IV. Concentration Calculationsa. The concentration of a solution is the quantity of a solute that is contained in aparticular quantity of solvent or solution. i. Knowing the concentration of solutes is important in controlling thestoichiometry of reactants for solution reactions.b. The most common unit of concentration is molarity, which is also the most usefulfor calculations involving the stoichiometry of reactions in solution.c. The molarity (M) is a common unit of concentration and is defined as thenumber of moles of solute present in exactly 1 L of solution. i. It is, equivalently, the number of millimoles of solute present in exactly 1mL of solution: d. In the lab you would prep the solution before the solvent Molarity (M) = moles soluteliters solution1. Calculate the number of moles of solute present.2. Calculate the number of liters of solution present.3. Divide the number of moles of solute by the number of liters of solution.ii. This is something you will simply need to practice. There are practice problems on pages 170 and at the end of chapter


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UofL CHEM 101 - Solutions

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