CHEM 1061 1st Edition Lecture 6 Outline of Last Lecture I Continuation of Empirical Formula II Molar Mass of a Compound III Writing and Balancing Chemical Equations IV Limiting Reactants Outline of Current Lecture V VI Percentage Yields Solution Stoichiometry a Diluting a Solution b Solubility c Ionic Compound in a solution d Moles of Ions in a Solution e Covalent Compounds in Water VII Writing Equations for Aqueous Ionic Compounds Current Lecture I II Percentage Yields a Useful in Labs but not covering in lecture b Page 123 in textbook sample problem 3 21 Solution Stoichiometry a Aqueous solutions are those that dissolve in WATER b Solute substance that is dissolved smaller quantity c Solvent what dissolves the solute larger quantity is often water d Concentration is written in units called Molarity M e Molarity Moles of a solute L of solution mol solute L soln These 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 f III SAMPLE PROBLEM What is the molarity of 500 mL of soln containing 21 2g KI Molar mass of KI is approx 166g mol Answer 0 255 M g Diluting a Solution i Only use if you have the SAME solution ii NOT if you are reacting two different solutions iii M1V1 M2V2 Concentrated initial Diluted iv Sample Problem 4 6 h Solubility i Dissolving substances in water ii EXAMPLE NaCl is soluble in water NaCl s H20 Na aq Cl aq iii Water is POLAR unequal sharing of electrons so the H are partially positive and the O are partially negative iv EXAMPLE AgCl s is insoluble in water AgCl s H2O AgCl s v Ionic bonds of AgCl are stronger than those of NaCl therefore they do not dissolve i Ionic Compound in a Solution i Soluble Ionic compounds are strong ELECTROLYTES ii Electrolytes substances that conduct a current when dissolved in water iii you NEED ions to conduct a current j Moles of Ions in Solution i How many moles of ions are released when 2 0 mol MgCl2 are dissolved in water MgCl2 H2O Mg 2 aq 2Cl aq 2 0mol MgCl2 x 1 mol Mg 2 1 mol MgCl2 2 0 mol Mg 2 2 mol MgCl2 x 2 mol Cl 1 mol MgCl2 4 0 mol Cl ANSWER 6 0 mol total ions k Covalent Compounds in Water i Substances can dissolve in H2O without separating into Ions ii Sucrose C12H22O14 s H2O C12H22O14 aq iii These are called NONELECTROLYTES does not conduct electrical current when dissolved in water Writing Equations for Aqueous Ionic Compounds a Three Reaction Types i Precipitation ii Acid Base iii Oxidation Redution Redox b Equations i Molecular ii Total Ionic iii Net Ionic c Precipitation i Forming a solid insoluble compound from soln aka precipitate ii Example Pb NO3 aq KI aq 1 Double displacement metathesis reaction 2 AB CD AD CB
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