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CHEM 211 MW 10:30-11:45 AM Prof. Gregory Foster Page 1 of 3Notes for Week of 10/2 I. Solute concentration – Molarity a. Molarity = mol of solute / L of solution b. Defines the concentration of the solute in the solvent c. Calculations 1. 26.8 g of NaCl is added to water forming a 500 mL solution. What is molar concentration of NaCl 2. Convert grams of solute to moles 3. Divide the mole amount by .5 L ii. Changing the concentration by diluting to 2 L 1. M1V1=M2V2 a. This tells us that the moles of solute will not change, only the volume does 2. M2=(M1V1)/V2 3. Gives us the now molar concentration iii. You remove 150 mL and dilute it to 2 L. New concentration of NaCl? 1. Use the M1V1 equation again 2. M2=M1V1/V2 3. Use the new volume that was removed for V1 iv. What is the concentration of Al3+ in .240 M Al2(SO4)3 1. .240 M Al2(SO4)3 * 2 mol Al3+/ 1 mol compound = .480 M Al3+ v. How many total ions in a 500 mL solution .240 M Al2(SO4)3 1. Molarity * Liters to find moles 2. Moles * 5 moles of ions/ 1 mol of compound 3. Moles of ions * avogadros number II. Ionic compounds & dissolution a. Strong electrolyte = 100% dissociation a. NaCl Na+ + Cl- is a strong electrolyte because it completely dissolves b. Weak electrolyte <100% dissociation a. HF H+ +F- is a very weak electrolyte bc only about 3% of it dissolves III. 3 broad categories of chemical reactions a. Precipitation Reactions i. Ba(NO3)2 (aq)+ Na2SO4(aq) BaSO4 + 2NaNO3 ii. If we add two soluble compounds together we typically get a precipitate iii. Double displacement 1. We re-pair the anions and cations with each other iv. How do we determine if something forms a precipitate? 1. Look at the solubility rules in table 4.1 2. If it doesn’t fall within the first three rules you should consider it insoluble v. Writing equations
CHEM 211 MW 10:30-11:45 AM Prof. Gregory Foster Page 2 of 31. Molecular a. When we have the compounds always expressed in the molecular form b. 2. Total ionic a. Rewrite everything as individual ions unless they are not dissolved 3. Net ionic a. Remove all the spectator ions vi. Calculating how much precipitate formed 1. First we have to convert moles of solute to moles of ion a. We do this by using the molarity of the ion multiplied by the volume of the solution 2. Then we do a limiting reactant equation because one of the ionic quantities will limit how much can be made b. Acid-Base reactions i. Any compound that releases H+ ions in a solution is an acid ii. Compounds that release Oh(hydroxide) is a base iii. Acid dissociation and proton transfer 1. HCl H+ and Cl- = strong acid, again strong is determined ny the amount of dissociation 2. NaOH Na+ + OH- iv. Strong acids 1. HCl, HBr, HI, HNO3, H2SO4, HClO4 v. Strong Base 1. Group 1 and 2 hydroxides vi. Hydronium ion is an example of proton transfer 1. HCl + H2O H3O + Cl 2. Same with a. NH3 + H2O OH + NH4 3. Acids are proton donors and bases are proton acceptors vii. Neutralization reactions. Acid + Base. Form water + salt. 1. Acid + Base H2O + Salt viii. Weak acid strong base neutralization reactions 1. c. Redox reactions i. Oxidation + reduction 1. Oxidation – loss of electrons, always paired with a reduction reaction 2. Reduction – gain of electrons ii. Oxidizing and reducing agents 1. Characterized by transfer of electrons as opposed to the previous reactions which didn’t have any transfer of electrons
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School: George Mason University
Course: General Chemistry 1
Professor: Paul Cooper
Term: Summer 2015
Tags: MCAT General Chemistry, General Chemistry, and Chemistry
Name: General Chemistry 1 Week 5
Description: These notes cover the in class notes from the week of October 2nd
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