What Is Required? You need to find the molar concentration, c, of the ions in a solution of ammonium phosphate.

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1 Chemistry 11 Solutios Sectio 9.2 Solutio Stoichiometry Solutios for Practice Problems Studet Editio page Practice Problem (page 417) If 8.5 g of pure ammoium phosphate, (NH 4 ) 3 PO 4 (s), is dissolved i distilled water to make 400 ml of solutio, what are the cocetratios (i moles per litre) of the ios i the solutio? You eed to fid the molar cocetratio, c, of the ios i a solutio of ammoium phosphate. What Is Give? You kow the volume of the ammoium phosphate solutio: 400 ml You kow the mass of ammoium phosphate, (NH 4 ) 3 PO 4 (s): 8.5 g Pla Your Strategy Write the balaced chemical equatio for the dissolutio of ammoium phosphate, (NH 4 ) 3 PO 4 (s). Determie the molar mass of (NH 4 ) 3 PO 4 (s). Calculate the amout i moles of (NH 4 ) 3 PO 4 (s) usig the relatioship. M Covert the volume from millilitres to litres: 1 ml = L Calculate the cocetratio of (NH 4 ) 3 PO 4 (aq) usig the relatioship c. Equate the mole ratios ad cross multiply to solve for, the amout i moles of (NH 4 ) 3 PO 4 (s). Act o Your Strategy Balaced equatio: (NH 4 ) 3 PO 4 (s) 3NH 4 + (aq) + PO 4 3 (aq) Mole ratio: 1 mole 3 moles 1 mole Molar mass, M, of (NH 4 ) 3 PO 4 (s): M 3 M 12 M 1 M 4M NH4 PO4 3 N H P O g/mol g/mol g / mol g/mol g/mol Chapter 9ReactiosiAqueousSolutios MHR 18

2 Chemistry 11 Solutios Amout i moles,, of (NH 4 ) 3 PO 4 (s): m NH4 PO 3 4 M 8.5 g g /mol o m l Amout i moles,, of NH + 4 (aq): 1 mol (NH ) PO mol (NH ) PO 3 mol NH NH4 NH4 3 mol NH mol (NH 4) PO 1 mol (NH 4) 3 PO mol Amout i moles,, of PO 3 4 (aq): 1 mol (NH ) PO mol (NH ) PO 3 1 mol PO PO4 3 PO mol PO mol (NH ) PO mol olume of solutio: ml 1 10 L/ ml L Cocetratio of NH + 4 ( aq): c mol L mol/l 0.04 mol/l mol (NH 4) 3 PO Chapter 9ReactiosiAqueousSolutios MHR 19

3 Chemistry 11 Solutios Cocetratio of PO 3 4 (aq): c mol L mol/l 0.01 mol/ L The cocetratio of the ammoium io, NH 4 + (aq), is 0.04 mol/l. The cocetratio of the phosphate io, PO 4 3 (aq), is 0.01 mol/l. Check Your Solutio The uits for amout ad cocetratio are correct. The aswer has oe sigificat digit ad seems reasoable. 12. Practice Problem (page 417) A strip of zic metal was placed i a beaker that cotaied 120 ml of a solutio of copper(ii) itrate, Cu(NO 3 ) 2 (aq). The mass of the copper produced was g. Fid the iitial cocetratio of the copper(ii) itrate solutio. You eed to fid the molar cocetratio, c, of the copper(ii) itrate solutio. What Is Give? You kow the volume of the copper(ii) itrate solutio: 120 ml You kow the mass of copper precipitated: g You kow the other reactat: zic Pla Your Strategy Write the chemical equatio for the sigle displacemet reactio. Use the periodic table to determie the atomic molar mass of Cu(s). Calculate the amout i moles of Cu(s) usig the relatioship. M Calculate the amout i moles of copper(ii) itrate usig the mole ratio i the balaced equatio. Covert the volume from millilitres to litres: 1 ml = L Calculate the cocetratio of copper(ii) itrate usig the relatioship c Chapter 9ReactiosiAqueousSolutios MHR 20

4 Chemistry 11 Solutios Amout i moles,, of the precipitate, FeS(s): 1 mol FeS FeS 1 mol Fe(NO ) mol Fe(NO ) FeS 1 mol FeS mol Fe(NO ) 1 mol Fe(NO 3 ) mol Molar mass, M, of the precipitate, FeS(s): M 1 M 1M FeS Fe S 1(55.85 g/mol) 1(32.07 g/mol) g/mol 3 2 Mass, m, of FeS(s): m M FeS mol g 1.10 g g/ mol The precipitate is iro(ii) sulfide, FeS(s), ad the maximum mass that ca be collected from the reactio is 1.10 g. Check Your Solutio The uits for amout ad cocetratio are correct. The aswer has three sigificat digits ad seems reasoable. 15. Practice Problem (page 417) What mass of silver chloride, AgCl(s), ca be precipitated from 75 ml of 0.25 mol/l silver itrate, AgNO 3 (aq), by addig excess magesium chloride, MgCl 2 (aq)? You eed to calculate the mass of silver chloride that will precipitate i a reactio. What Is Give? You kow the volume of the silver itrate solutio: 75 ml You kow the iitial cocetratio of silver itrate: 0.25 mol/l You kow the other reactat is aqueous magesium chloride, MgCl 2 (aq) Chapter 9ReactiosiAqueousSolutios MHR 25

5 Chemistry 11 Solutios Pla Your Strategy Predict the other product that forms i this double displacemet reactio. Write the balaced equatio for the reactio. Covert the volume to litres: 1 ml = L Calculate the amout i moles of silver itrate usig the relatioship c. Equate the mole ratios ad solve for the amout i moles of precipitate. Use the periodic table to determie the molar mass of the precipitate. Calculate the mass of precipitate usig the relatioship m M. Act o Your Strategy The other product is magesium itrate, Mg(NO 3 ) 2 (aq). Balaced equatio: MgCl 2 (aq) + 2AgNO 3 (aq) Mg(NO 3 ) 2 (aq) + 2AgCl(s) Mole ratio: 1 mole 2 moles 1 mole 2 moles olume of solutio: 3 75 ml 1 10 L/ ml L Amout i moles,, of AgNO 3 (aq): c AgNO mol / L L mol Amout i moles,, of precipitate, AgCl(s): 2 mol AgCl AgCl 2 mol AgNO mol AgNO AgCl mol AgCl mol AgNO 2 mol AgNO mol Molar mass, M, of the precipitate, AgCl(s): M 1 M 1M AgCl Ag Cl g/mol 1(35.45 g/mol) g/mol Chapter 9ReactiosiAqueousSolutios MHR 26

6 Chemistry 11 Solutios Mass, m, of AgCl(s): m M AgCl mol g 2.7 g g/ mol Chapter 9ReactiosiAqueousSolutios MHR 27 The mass of silver chloride that ca be precipitated is 2.7 g. Check Your Solutio The uits for amout ad cocetratio are correct. The aswer has two sigificat digits ad seems reasoable. 16. Practice Problem (page 417) What mass of bromie gas ca be collected by bubblig excess chlorie gas through 850 ml of a mol/l solutio of sodium bromide, NaBr(aq)? You eed to calculate the mass of bromie gas that will collect i a reactio. What Is Give? You kow the volume of the sodium bromide solutio: 850 ml You kow the iitial cocetratio of the sodium bromide solutio: mol/l You kow the other reactat: chlorie gas, Cl 2 (aq) Pla Your Strategy Predict the ame ad formula for the other product that forms i this sigle displacemet reactio. Write the balaced equatio for the reactio. Covert the volume from millilitres to litres: 1 ml = L Calculate the amout i moles of sodium bromide solutio usig the relatioship c. Equate the mole ratios ad solve for the amout i moles of bromie gas. Use the periodic table to determie the molar mass of the bromie gas, Br 2 (g). Calculate the mass of bromie gas usig the relatioship m M. Act o Your Strategy The other product that forms i this sigle displacemet reactio is sodium chloride, NaCl(aq). Balaced equatio: Cl 2 (g) + 2NaBr(aq) 2NaCl (aq) + Br 2 (g) Mole ratio: 1 mole 2 moles 2 moles 1 mole

7 Chemistry 11 Solutios Mass, m, of NaCl(s): m mol NaCl g 12.5 g g/ mol The mass of sodium chloride i the 1.0 L volumetric flask is 12.5 g. Check Your Solutio The uits for amout ad cocetratio are correct. The aswer has three sigificat digits ad seems reasoable. 20. Practice Problem (page 417) Food maufacturers sometimes add calcium acetate, Ca(CH 3 COO) 2 (s), to sauces as a thickeig aget. Whe aalyzed, a 250 ml solutio of calcium acetate was foud to cotai mol of acetate ios. a. Fid the molar cocetratio of the calcium acetate solutio. b. What mass of calcium acetate was dissolved to make the solutio? a. molar cocetratio You eed to fid the molar cocetratio of a calcium acetate solutio. What Is Give? You kow the chemical formula for calcium acetate: Ca(CH 3 COO) 2 (s) You kow the amout i moles of acetate ios, CH 3 COO (aq): mol You kow the volume of the solutio: 250 ml Pla Your Strategy Use the mole ratio of acetate ios to calcium acetate to determie the amout i moles of calcium acetate. Covert the volume from millilitres to litres: 1 ml = L Calculate the cocetratio of calcium acetate usig the relatioship c. Act o Your Strategy The chemical formula for calcium acetate, Ca(CH 3 COO) 2 (s), idicates that there are two CH 3 COO ios for oe formula uit of Ca(CH 3 COO) 2 (s) Chapter 9ReactiosiAqueousSolutios MHR 35

8 Chemistry 11 Solutios Amout i moles,, of Ca(CH 3 COO) 2 (s): 1 mol Ca(CH3COO) 2 Ca(CH3COO) 2 2 mol CH COO mol CH COO 3 3 Ca(CH3COO) 2 olume of solutio: 250 ml L 1 mol Ca(CH3COO) mol CH3COO 2 mol CH COO mol L/ ml Cocetratio of Ca(CH 3 COO) 2 (aq): c mol L 0.40 mol/l The cocetratio of calcium acetate is 0.40 mol/l. b. mass of calcium acetate You eed to fid the mass of calcium acetate i 250 ml of solutio. What Is Give? You kow the molar cocetratio: 0.40 mol/l You kow the volume of solutio: L Pla Your Strategy Calculate the amout i moles of calcium acetate usig the relatioship the relatioship c. Use the periodic table to fid the molar mass of Ca(CH 3 COO) 2 (s). Calculate the mass of calcium acetate usig the relatioship m M Chapter 9ReactiosiAqueousSolutios MHR 36

9 Chemistry 11 Solutios Act o Your Strategy Amout i moles,, of Ca(CH 3 COO) 2 (aq): CaCH3COO 2 c 0.40 mol/ L L 0.10 mol Molar mass, M, of Ca(CH 3 COO) 2 (s): M 1 M 4 M 6 M 4M Ca CH COO 3 2 Ca C H O g/mol g/mol g/mol g/mol g/mol Mass, m, of Ca(CH 3 COO) 2 (s): m M 3 2 Ca CH COO 0.10 mol g/ mol g 16 g The mass of calcium acetate is 16 g. Check Your Solutio The uits for amout ad cocetratio are correct. The aswer has two sigificat digits ad seems reasoable. Sectio 9.2 Solutio Stoichiometry Solutios for Practice Problems Studet Editio page Practice Problem (page 420) Lead(II) sulfide, PbS(s), is a black, isoluble substace. Calculate the maximum mass of lead(ii) sulfide that will precipitate whe 6.75 g of sodium sulfide, Na 2 S(s), is added to 250 ml of mol/l lead(ii) itrate, Pb(NO 3 ) 2 (aq). You eed to fid the mass of lead(ii) sulfide that will precipitate Chapter 9ReactiosiAqueousSolutios MHR 37

Check Your Solution The units for amount and concentration are correct. The answer has two significant digits and seems reasonable.

Check Your Solution The units for amount and concentration are correct. The answer has two significant digits and seems reasonable. Act o Your Strategy Amout i moles,, of Ca(CH 3 COO) 2 (aq): CaCH3COO 2 c V 0.40 mol/ L 0.250 L 0.10 mol Molar mass, M, of Ca(CH 3 COO) 2 (s): M 1 M 4 M 6 M 4M Ca CH COO 3 2 Ca C H O 1 40.08 g/mol 4 12.01