Solutions in Chemical Reactions Chapter 12 Solutions 12.6 Solutions in Chemical Reactions Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

Molarity in Chemical Reactions In a chemical reaction, The volume and molarity of a solution are used to determine the moles of a reactant or product. volume (L) x molarity ( mol ) = moles 1 L If molarity (mol/L) and moles are given, the volume (L) can be determined mol x 1 L = volume (L) mol

Using Molarity of Reactants How many mL of 3.00 M HCl are needed to react 4.85 g CaCO3? 2HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l) STEP 1 Given 3.00 M HCl; 4.85 g CaCO3 Need volume in mL STEP 2 Plan g CaCO3 mol CaCO3 mol HCl mL HCl

Using Molarity of Reactants (cont.) 2HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l) STEP 3 Equalitites 1 mol CaCO3 = 100.09 g; 1 mol CaCO3 = 2 mol HCl 1000 mL HCl = 3.00 mol HCl STEP 4 Set Up 4.85 g CaCO3 x 1 mol CaCO3 x 2 mol HCl x 1000 mL HCl 100.09 g CaCO3 1 mol CaCO3 3.00 mol HCl = 32.3 mL HCl required

Learning Check How many mL of a 0.150 M Na2S solution are needed to react 18.5 mL of 0.225 M NiCl2 solution? NiCl2(aq) + Na2S(aq) NiS(s) + 2NaClaq) 1) 4.16 mL 2) 6.24 mL 3) 27.8 mL

Solution 3) 27.8 mL 0.0185 L x 0.225 mol NiCl2 x 1 mol Na2S x 1000 mL 1 L 1 mol NiCl2 0.150 mol = 27.8 mL Na2S solution

Learning Check What is the molarity if 15.0 mL of AgNO3 solution reacts with 22.8 mL of 0.100 M MgCl2? MgCl2(aq) + 2AgNO3(aq) 2AgCl(s) + Mg(NO3)2(aq) 1) 0.0760 M 2) 0.152 M 3) 0.304 M

Solution 3) 0.304 M AgNO3 0.0228 L x 0.100 mol MgCl2 x 2 mol AgNO3 x 1 = 1 L 1 mol MgCl2 0.0150 L = 0.304 mol/L = 0.304 M AgNO3

Learning Check How many liters of H2 gas at STP are produced when 12.5 g Zn react with 20.0 mL of 1.50 M HCl? Zn(s) + 2HCl(aq) ZnCl2 (aq) + H2(g) 1) 4.28 L H2 2) 0.336 L H2 3) 0.168 L H2

Solution 2) 0.336 L H2 Limiting Reactant 12.5 g Zn x 1.00 mol Zn x 1 mol H2 x 22.4 L = 4.28 L H2 65.41 g Zn 1 mol Zn 1 mol 0.0200 L x 1.50 mol HCl x 1 mol H2 x 22.4 L 1 L 2 mol HCl 1 mol = 0.336 L H2 gas

Summary of Chemical Reactions Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings