Chapter 4A

# Chapter 4A - Chapter 4: Chemical Quantities and Aqueous...

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Reaction Stoichiometry: Stoichiometry tells us quantitative mass relationships in a chemical reaction. It answers the questions: How much of each reactant is consumed in a chemical reaction? How much of each product is produced in a chemical reaction? Balanced Chemical equations: Ammonia (NH 3 ) reacts with oxygen (O 2 ) to yield nitrogen monoxide (NO) and water (H 2 O) NH 3 + O 2 NO + H 2 O Unbalanced equation Chapter 4: Chemical Quantities and Aqueous Reactions NH 3 + O 2 NO + H 2 O 4 5 4 6 Stoichiometric coefficients Balanced chemical eq These coefficients specify the relative amounts in moles (or molecules) of each of the substances involved in a chemical reaction

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Stoichiometry and mass relationship (1). Moles of sulfur=[67.2g/(32.066g/mol)]=2.0957 (2). Use stoichiometry: Problem: In the reaction given below, what mass of CS 2 can be generated by the complete reaction of 67.2g of sulfur. CH 4 + 4S CS 2 + 2H 2 S 4 mol S give 1 mol CS 2 2.0957 mol S give Y mol CS 2 4 mol S x Y mol CS 2 =2.0957 mol S x 1 mol CS 2 Y=(2.0957 x ( 1/4) =0.5239 (3). Mass of CS 2 =0.5239 mol x 76.143 g/mol = 39.9 g
Stoichiometry and volume relationship Problem :What volume of O 2 is required to generate 16.4 L of NO in the reaction, 4 NH 3 + 5 O 2 4 NO + 6 H 2 O Assume that volumes are measured at constant T and P. (a).Use stoichiometry 4 mol of NO are obtained from 5 mol O 2 (b).Use “Equal volumes of gases contain equal number of particles” at a given T and P 4 L of NO are obtained from 5 L of O 2 16.4 L of NO are obtained from Y L of O 2 4 L NO x Y L O 2 =5 L O 2 x 16.4 L NO Y=16.4 x (5/4)=20.5 L

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Problem : Density of Si 4 H 10 is 0.825 g/cc.What mass of SiO 2 is generated when 25.00 cc of Si 4 H 10 reacted completely in the reaction, 2 Si 4 H 10 + 13 O 2 8 SiO 2 + 10 H 2 O mass of Si 4 H 10 reacted =25.00 cc x 0.825 g/cc=20.625g moles of Si 4 H 10 reacted = 20.625 g/(122.423g/mol) =0.1685 2 mol Si 4 H 10 give 8 mol SiO
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## This note was uploaded on 02/27/2009 for the course CHEM 102a taught by Professor Hanusa during the Fall '06 term at Vanderbilt.

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Chapter 4A - Chapter 4: Chemical Quantities and Aqueous...

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