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

Size: px

Start display at page:

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

Rudolph O’Neal’
6 years ago
Views:

1 Act o Your Strategy Amout i moles,, of Ca(CH 3 COO) 2 (aq): CaCH3COO 2 c V 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). What Is Required? You eed to fid the mass of lead(ii) sulfide that will precipitate Chapter 9ReactiosiAqueousSolutios MHR 37

2 What Is Give? You kow the mass of the sodium sulfide solutio: 6.75 g You kow the volume of the lead(ii) itrate solutio: 250 ml You kow the cocetratio of the lead(ii) itrate solutio: mol/l Pla Your Strategy Write the balaced chemical equatio for the reactio. Determie the molar mass of Na 2 S(s). Calculate the amout i moles of each reactat. To allow for the mole ratio of the reactats, divide the amout of each reactat by its coefficiet i the chemical equatio. The smaller result idetifies the limitig reactat. Use the mole ratio i the balaced equatio ad the amout i moles of the limitig reactat to fid the amout i moles of the precipitate. Determie the molar mass of PbS(s). Calculate the mass of PbS(s) usig the relatioship m M. Act o Your Strategy Balaced chemical equatio: Na 2 S(s) + Pb(NO 3 ) 2 (aq) 2NaNO 3 (aq) + PbS(s) Amout i moles,, of Na 2 S(s): Na2S M 6.75 g g /mol o m l Molar mass, M, of Na 2 S(s): M 2M 1M Na2S Na S g/mol g/mol g/mol Amout i moles,, of Pb(NO 3 ) 2 (aq): c V Pb NO mol/ L L mol Chapter 9ReactiosiAqueousSolutios MHR 38

3 Idetificatio of the limitig reactat: amout of Na 2S mol coefficiet mol 2 amout of Pb(NO 3) mol coefficiet mo Pb(NO 3 ) 2 (aq) is the limitig reactat because it is the smaller amout. Amout i moles,, of the precipitate, PbS(s): 1 mol Pb(NO ) mol Pb(NO ) 1 mol PbS PbS Molar mass, M, of PbS(s): M 1 M 1M PbS Pb S PbS 1 mol PbS mol Pb(NO 3) mol 1 mol Pb(NO 3) g/mol g/mol g / mol Mass, m, of PbS(s): m M PbS g/ mol mol g 12 g The mass of lead(ii) sulfide that precipitates is 12 g. Check Your Solutio The mass of precipitate seems reasoable compared with the umber of moles of reactat used i this reactio. The aswer correctly shows two sigificat digits. l Chapter 9ReactiosiAqueousSolutios MHR 39

22. Practice Problem (page 420) Silver chromate, Ag 2 CrO 4 (s), is a brick-red isoluble substace that is used to stai euros so that they ca be viewed uder a microscope.

4 22. Practice Problem (page 420) Silver chromate, Ag 2 CrO 4 (s), is a brick-red isoluble substace that is used to stai euros so that they ca be viewed uder a microscope. Silver chromate ca be formed by the reactio betwee silver itrate, AgNO 3 (aq), ad potassium chromate, K 2 CrO 4 (aq), as show i the photograph below. Calculate the mass of silver chromate that forms whe 25.0 ml of mol/l silver itrate reacts with 20.0 ml of mol/l potassium chromate. What Is Required? You eed to fid the mass of silver chromate that will precipitate. What Is Give? You kow the volume of the silver itrate solutio: 25.0 ml You kow the cocetratio of the silver itrate solutio: mol/l You kow the volume of the potassium chromate solutio: 20.0 ml You kow the cocetratio of the potassium chromate solutio: mol/l Pla Your Strategy Write the balaced chemical equatio for the reactio. Calculate the amout i moles of each reactat usig the relatioship c V. To allow for the mole ratio of the reactats, divide the amout of each reactat by its coefficiet i the chemical equatio. The smaller result idetifies the limitig reactat. Use the mole ratios to fid the amout i moles,, of the precipitate. Determie the molar mass of Ag 2 CrO 4 (s). Calculate the mass of Ag 2 CrO 4 (s) usig the relatioship m M Chapter 9ReactiosiAqueousSolutios MHR 40

5 Amout i moles,, of Na 2 CO 3 (aq): 1 mol Ba mol Ba 1 mol Na CO Na2CO3 Na2CO3 1 mol Na 2CO mol Ba 2 1 mol Ba mol Molar mass, M, of Na 2 CO 3 (s): M 2 M 1 M 3M Na2CO3 Na C O g/mol g/mol g/mol g/mol Mass, m, of Na 2 CO 3 (s): m M Na2CO mol g g g/ mol The mass of sodium carboate required is g. Check Your Solutio The mass is correctly expressed i grams ad shows three sigificat digits. This aswer seems reasoable based upo the mole ratio i the balaced equatio ad the quatity of reactat that has bee give. 25. Practice Problem (page 420) What is the maximum mass of lead(ii) iodide, PbI 2 (s), that ca precipitate whe 40.0 ml of a mol/l solutio of lead(ii) itrate, Pb(NO 3 ) 2 (aq), is mixed with 85.0 ml of a mol/l solutio of potassium iodide, KI(aq)? Why might the actual mass precipitated be less? What Is Required? You eed to the fid the maximum mass of lead iodide that will precipitate whe solutios of lead(ii) itrate ad potassium iodide are mixed Chapter 9ReactiosiAqueousSolutios MHR 45

6 What Is Give? You kow the volume of the potassium iodide solutio: 85.0 ml You kow the cocetratio of the potassium iodide solutio: mol/l You kow the volume of the lead(ii) itrate solutio: 40.0 ml You kow the cocetratio of the lead(ii) itrate solutio: mol/l Pla Your Strategy Write the balaced chemical equatio for the reactio. Calculate the amout i moles of each reactat usig the relatioship the relatioship c V. To allow for the mole ratio of the reactats, divide the amout of each reactat by its coefficiet i the chemical equatio. The smaller result idetifies the limitig reactat. Use the mole ratio i the balaced equatio ad the amout i moles of the limitig reactat to fid the amout i moles of the precipitate, PbI 2 (s). Determie the molar mass of PbI 2 (s). Calculate the mass of PbI 2 (s) usig the relatioship m M. Act o Your Strategy Balaced chemical equatio: 2KI(aq) + Pb(NO 3 ) 2 (aq) 2KNO 3 (aq) + PbI 2 (s) Amout i moles,, of KI(aq): c V KI mol/ L L mol Amout i moles,, of Pb(NO 3 ) 2 (aq): c V Pb NO mol/ L L mol Idetificatio of limitig reactat: amout of KI mol coefficiet mol 2 amout of Pb(NO 3) mol coefficiet mol Chapter 9ReactiosiAqueousSolutios MHR 46

7 KI(aq) is the limitig reactat because it is the smaller amout. Amout i moles,, of the precipitate, PbI 2 (s): 2 mol KI mol KI 1 mol PbI PbI2 2 PbI2 1 mol PbI mol KI mol Molar mass, M, of PbI 2 (s): M 1 M 2M PbI2 Pb I 2 mol KI g/mol g/mol g / mol Mass, m, of PbI 2 (s): m M PbI mol g 4.11 g g/ mol The maximum mass of lead(ii) iodide that precipitates is 4.11 g. Oe reaso that the mass of PbI 2 (s) could be less tha this amout is that a small amout of solid lead iodide dissolves. I additio, if the mass of precipitate was obtaied by filterig, some of the precipitate could pass through the filter paper with the filtrate, resultig i a lower recovered mass of precipitate. Check Your Solutio The mass of precipitate seems reasoable compared with the amout i moles of the reactat used i this reactio. The aswer correctly shows three sigificat digits Chapter 9ReactiosiAqueousSolutios MHR 47

8 Amout i moles,, of the precipitate, CaCO 3 (s): 1 mol CaCl mol CaCl 2 1 mol CaCO 3 CaCO3 CaCO3 1 mol CaCO mol CaCl 1 mol CaCl mol Molar mass, M, of CaCO 3 (s): M 1 M 1 M 3M CaCO3 Ca C O g/mol g/ mol g/mol g / mol Mass, m, of CaCO 3 (s): m M CaCO mol g g/ mol The mass of calcium carboate that precipitates is g. Check Your Solutio The mass of precipitate seems reasoable compared with the amout i moles of reactat used. The aswer correctly shows three sigificat digits. 30. Practice Problem (page 420) Barium chromate, BaCrO 4 (s), is a isoluble yellow solid. Determie the cocetratio of barium ios i a solutio made by mixig 50.0 ml of a mol/l solutio of barium itrate, Ba(NO 3 ) 2 (aq), with 50.0 ml of a mol/l solutio of potassium chromate, K 2 CrO 4 (aq). What Is Required? You eed to fid the cocetratio of barium ios remaiig i a solutio. What Is Give? You kow the volume of the barium itrate solutio: 50.0 ml You kow the cocetratio of the barium itrate solutio: mol/l You kow the volume of the potassium chromate solutio: 50.0 ml You kow the cocetratio of the potassium chromate solutio: mol/l Chapter 9ReactiosiAqueousSolutios MHR 54

9 Pla Your Strategy Write the balaced chemical equatio for the reactio. Calculate the amout i moles of each reactat usig the relatioship c V. To allow for the mole ratio of the reactats, divide the amout of each reactat by its coefficiet i the chemical equatio. The smaller result idetifies the limitig reactat. Determie the amout i moles of Ba(NO 3 ) 2 (aq) i excess. Determie the amout i moles of Ba 2+ (aq) per mole of Ba(NO 3 ) 2 (aq). Determie the amout i moles of Ba 2+ i excess. Calculate the total volume of the mixture ad determie the cocetratio of Ba 2+ (aq). Act o Your Strategy Balaced equatio: Ba(NO 3 ) 2 (aq) + K 2 CrO 4 (aq) 2KNO 3 (aq) + BaCrO 4 (s) Mole ratio 1 mole 1 mole 2 mole 1 mole Amout i moles,, of Ba(NO 3 ) 2 (aq): c V Ba NO mol/ L L mol Amout i moles,, of K 2 CrO 4 (aq): c V K2CrO mol/ L L mol = mol/ L L Idetificatio of the limitig reactat: amout of Ba(NO 3) mol coefficiet mol amout of K2CrO mol coefficiet mo Ba(NO 3 ) 2 (aq) is the limitig reactat because it is the smaller amout. l Chapter 9ReactiosiAqueousSolutios MHR 55

10 Sice the mole ratio of Ba(NO 3 ) 2 (aq) to K 2 CrO 4 (aq) is 1:1, the excess amout i moles,, of Ba(NO 3 ) 2 (aq) is the differece betwee the amout i moles of the two reactats. BaNO excess Ba NO K2CrO mol mol mol Amout i moles,, of Ba 2+ (aq): 2 2 Ba 1 mol Ba mol Ba NO 1 mol Ba NO Ba mol Ba NO o 1 mol Ba(NO m l ) mol Ba 2 Total volume of mixture: V = 50.0 ml ml = ml = L Cocetratio of Ba 2+ (aq): c V mol L mol/l The cocetratio of barium ios remaiig i solutio is mol/l. Check Your Solutio The uits i the calculatios have cacelled properly ad the fial uit is correct. The cocetratio of the barium io i excess seems reasoable. The aswer correctly shows three sigificat digits Chapter 9ReactiosiAqueousSolutios MHR 56

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

What Is Required? You need to find the molar concentration, c, of the ions in a solution of ammonium phosphate. Chemistry 11 Solutios Sectio 9.2 Solutio Stoichiometry Solutios for Practice Problems Studet Editio page 417 11. Practice Problem (page 417) If 8.5 g of pure ammoium phosphate, (NH 4 ) 3 PO 4 (s), is dissolved