Ch5_D_Solutions

# Ch5_D_Solutions - REACTIONS IN SOLUTION Section 5.5 PROBLEM...

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Unformatted text preview: REACTIONS IN SOLUTION Section 5.5 PROBLEM: Dissolve 5.00 g of NiCl 22•6 H22O in PROBLEM: Dissolve 5.00 g of NiCl •6 H O in enough water to make 250 mL of solution. enough water to make 250 mL of solution. Calculate molarity. Calculate molarity. Terminology Terminology In solution we need to define the • SOLVENT the component whose physical state is preserved when solution forms • SOLUTE the other solution component The Nature of the KMnO 44 Solution The Nature of the KMnO Solution Step 2: Calculate molarity Step Calculate [NiCl2•6 H2O ] = 0.0841 M Molarity(M) = moles solute liters of solution The Nature of a Na 22CO33 Solution The Nature of a Na CO Solution 3 Na 2CO3 Na 1 mol = 0 .0210 mol 237.7 g 0.0210 mol = 0 .0841 M 0.250 L The amount of solute in a solution is given by its concentration. is concentration This water-soluble compound is ionic Na2CO3(aq) --> 2 Na+(aq ) + CO32-(aq) Step 1: Calculate moles Step Calculate of NiCl2•6H2O 5.00 g • Concentration of Solute Concentration of Solute KMnO4(aq) --> K+(aq) + MnO4-(aq) If [KMnO4 ] = 0.30 M, then [K+] = [MnO 4-] = 0.30 M Page 1 If [Na2CO3] = 0.100 M, then [Na+] = 0.200 M [CO32-] = 0.100 M USING MOLARITY USING MOLARITY USING MOLARITY USING MOLARITY What mass of oxalic acid, H 2C2O4, is required to make 250. mL of a 0.0500 M solution? Because Conc (M) = moles/volume = mol/V this means that moles = M • V What mass of oxalic acid, H2C2O4, is What required to make 250. mL of a 0.0500 M solution? moles = M • V Step 1: Calculate moles of acid Step Calculate required. (0.0500 mol/L)(0.250 L) = 0.0125 mol Step 2: Calculate mass of acid Step Calculate required. (0.0125 mol )(90.00 g/mol) = PROBLEM: You have 50.0 mL of 3.0 M PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What NaOH and you want 0.50 M NaOH. What do you do? do you do? Add water to the 3.0 M solution to lower its concentration to 0.50 M Dilute the solution! 1.13 g 1.13 PROBLEM: You have 50.0 mL of 3.0 M PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What NaOH and you want 0.50 M NaOH. What do you do? do you do? H2 O But how much water But do we add? do Preparing Solutions Preparing Solutions • Weigh out a solid solute and dissolve in a given quantity of solvent. • Dilute a concentrated solution to give one that is less concentrated. PROBLEM: You have 50.0 mL of 3.0 M PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What NaOH and you want 0.50 M NaOH. What do you do? do you do? How much water is added? The important point is that ---> moles of NaOH in ORIGINAL solution = moles of NaOH in FINAL solution 3.0 M NaOH Concentrated 0.50 M NaOH Dilute Page 2 PROBLEM: You have 50.0 mL of 3.0 M PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What NaOH and you want 0.50 M NaOH. What do you do? do you do? PROBLEM: You have 50.0 mL of 3.0 M PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What NaOH and you want 0.50 M NaOH. What do you do? do you do? Moles of NaOH in original solution = M•V = Conclusion: H2 O add 250 mL of water to (3.0 mol/L)(0.050 L) = 0.15 mol NaOH Therefore, moles of NaOH in final solution must also = 0.15 mol NaOH (0.15 mol NaOH)(1 L/0.50 mol) = 0.30 L or 300 mL = volume of final solution or 300 3.0 M NaOH Concentrated 50.0 mL of 3.0 M NaOH to make 300 mL of 0.50 M 0.50 M NaOH NaOH. Dilute Page 3 Preparing Solutions Preparing Solutions by Dilution by Dilution A shortcut Minitial • Vinitial = Mfinal • Vfinal ...
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