Chemistry 110 CHEM 110
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This 4 page Class Notes was uploaded by Mikaela Notetaker on Monday March 21, 2016. The Class Notes belongs to CHEM 110 at West Virginia University taught by Melissa G. Ely in Spring 2016. Since its upload, it has received 8 views. For similar materials see Introduction to Chemistry in Chemistry at West Virginia University.
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Date Created: 03/21/16
Quiz 5 Chemical Equation: Shorthand way of specifying a chemical reaction. Reactants (left side) -> Products (right side) All chemical equations must be balanced: 1. Material balance: number of atoms of each element must be the same on both sides of the equation. 2. Charge Balance: net charge on reactant side must be equal to net charge on product side, A. SO +2O (fo2r oxygen) -> SO (oxygen 3hree) a. 2 SO + 2 (2 s2lfur, 6 oxygen)-> 2 SO (2 sulfur3 6 oxygen) b. The equation is now balanced. c. Charge is balanced and equal to zero. B. (NH )4 2 O2->7Cr O + 2 3 4 H 2 2 a. (2 N, 8 H, 2 Cr, 7 O) -> (2 N, 8 H, 2 Cr, 7 O) balanced b. Charge is also balanced and equal to zero. To Balance: 1. Adjust coefficients, never change subscripts! a. 2 C + O -> 2 CO 2 2. Start with most complicated substance first or start with element that appears in only one substance on each side. 3. Balance polyatomic ions as a group (do NOT split it up). 4. By convention, write the lowest set of whole number coefficients. 5. Balance H and O last. A. N 2 O -> 2 O 2 5 a. 2 N +25 O -> 22N O (4 N2+ 50 O -> 4 N 10 O) Interpretation of coefficients in balanced equation: 2N + 5O ->22N O 2 2 5 Can interpret coefficients in terms of atoms, molecules, and f.u. or in terms of moles: Stoichiometry: The coefficients allow us to convert between amounts of reactants and products. Consider the balanced equation: 2 N + 5 O 2> 2 N O2 2 5 A. How many moles of N O can 2e5produced by the reaction of 2.5 mol of O 2 with excess N ? 2 a. B. How many moles of N O can2b5 produced by the reaction of 7.71 mol of N with 2 excess O ? 2 a. C. How many moles of O are 2eeded to react with 0.733 mol of N ? 2 a. Consider the unbalanced equation: NO + H O -2 NH + O 3 2 A. 4 NO + 6 H O -2 4 NH 3 5 O 2 a. (4 N, 12 H, 10 O) -> (4 N, 12 H, 10 O) B. How many moles of NH a3e formed from 0.373 mol NO reacting with excess water? a. C. How many moles of water are needed to react with 1.57 mol NO? a. D. If 3.0 mol of NH w3s produced how many moles of O was also 2roduced? a. Limiting Reagent Problems 1. Limiting reagent a. Limits amount of product formed. b. All used up during the reaction. 2. Excess reagent a. Does not limit amount of product formed b. Some is left over after the reaction 3. Ex. 8 wheels(excess) + 3 frames(limiter) -> 3 bikes Consider the unbalanced equation: TiCl + Mg4-> Ti + MgCl 2 A. TiCl4+ 2 Mg -> Ti + 2 MgCl 2 a. (1 Ti, 4 Cl, 2 Mg) -> (1 Ti, 4 Cl, 2 Mg) B. How many moles of Ti can be produced by the reaction of 3.5 mol of Mg with 2.0 mol of TiCl 4 a. Step 1 is to convert the reactants to moles but they are already moles b. Step 2 is to convert each reactant to product amount. Step 3 is to name the limiting reagent. Consider the balanced equation: 2 H S2+ SO -> 2 3 S + 2 H O2 A. How much sulfur can be formed by the reaction of 0.700 mol H S2with 0.450 mol SO ?2 a. All of the reactants are already in moles so we can continue onto step two and three. b.