What Is Given? You know the solubility of magnesium fluoride is mol/l. [Mg 2+ ] = [MgF 2 ] = mol/l

Size: px

Start display at page:

Download "What Is Given? You know the solubility of magnesium fluoride is mol/l. [Mg 2+ ] = [MgF 2 ] = mol/l"

Hilda Small
5 years ago
Views:

1 122. Magesium fluoride, MgF 2 (aq) has a molar solubility of mol/l. Use this iformatio to determie the K sp value for the solid. You eed to calculate the K sp for magesium fluoride, MgF 2. You kow the solubility of magesium fluoride is mol/l. Write a balaced equatio for the solubility MgF 2 (s) Mg 2+ (aq) + 2F (aq) equilibrium. Write the expressio for the K sp. K sp = [Mg 2+ ][F ] 2 Determie the cocetratio of each io. 1 mol of MgF 2 (s) ioizes to give 1 mol of Mg 2+ ad 2 mol F io. Substitute the io cocetratios ito the K sp expressio ad solve. [Mg 2+ ] = [MgF 2 ] = mol/l [F ] = 2[MgF 2 ] = mol/l = mol/l K sp = [Mg 2+ ][F ] 2 = ( )( ) 2 = The calculated value of K sp has the correct umber of sigificat digits that agrees with the give data. The small value is expected for a compoud of low solubility. 316 MHR Chemistry 12 Solutios Maual

2 123. Silver sulfide, Ag 2 S(aq) has a K sp value that is equal to What is the molar solubility of the solid? You eed to calculate the molar solubility of silver sulfide, Ag 2 S(s). You kow the K sp for silver sulfide is Write the balaced equatio for the Write the solubility product equatio. Let x represet the molar solubility of Ag 2 S(s). Summarize the solubility of the Ag + (aq) ad S 2 (aq) ios at equilibrium i a ICE table. Ag 2 S(s) 2Ag + (aq) + S 2 (aq) K sp = [Ag + ] 2 [S 2 ] See the ICE table below. Ag 2 S(s) 2Ag + (aq) + S 2 (aq) [Ag + ] (mol/l) [S 2 ] (mol/l) I C x +2x +x E 2x x Write the expressio for the K sp ad solve for x. K sp = [Ag + ] 2 [S 2 ] = (2x) 2 (x) = 4x 3 x = mol/l The solubility is low as expected for a compoud with the give K sp. The aswer correctly shows 2 sigificat digits. Uit 4 Part B MHR 317

3 124. The K sp value for lead(ii) bromide, PbBr 2 (aq), is What is the solubility of the solid? You eed to calculate the solubility of lead(ii) bromide(s) i g/l. You kow the K sp for lead(ii) bromide is Write the balaced equatio for the Write the solubility product equatio. Let x represet the molar solubility of PbBr 2 (s). Summarize the solubility of the Pb 2+ (aq) ad Br (aq) ios at equilibrium i a ICE table. PbBr 2 (s) Pb 2+ (aq) + 2Br (aq) K sp = [Pb 2+ ][Br ] 2 See the ICE table below. PbBr 2 (s) Pb 2+ (aq) + 2Br (aq) [Pb 2+ ] (mol/l) [Br ] (mol/l) I C x +x +2x E x 2x Write the expressio for the K sp expressio ad solve for x. Determie the molar mass, M, of PbBr 2 ad express the solubility i g/l (m = M). K sp = [Pb 2+ ][Br ] 2 x x 2 3 4x 2 x mol/l mol /L g/ mol 4.3 g/l The solubility is low as expected for a compoud with the give K sp. The aswer correctly shows 2 sigificat digits. 318 MHR Chemistry 12 Solutios Maual

4 125. Which solid ca have more mass ioize ito 1.00 L of solutio: silver chloride, AgCl(s), or copper(i) chloride, CuCl(s)? You eed to compare the solubility of silver chloride ad copper(i) chloride i g/l. From Appedix B, the K sp for silver chloride is ad for copper(i) chloride is Write the balaced equatio for the solubility equilibrium of silver chloride. Write the solubility product equatio. Let x represet the molar solubility of AgCl(s). Write the expressio for the K sp. Let x represet the cocetratios of Ag + ad Cl. Solve for x. Determie the molar mass, M, of AgCl ad express the solubility i g/l (m = M). Repeat these steps for CuCl(s) ad determie which will have the greater mass dissolved i 1 L of solutio. AgCl(s) Ag + (aq) + Cl (aq) K sp = [Ag + ][Cl ] Ksp Ag Cl ( x)( x) 2 x x mol/l mol /L g/ mol g/l CuCl(s) Cu + (aq) + Cl (aq) Ksp Cu Cl ( x)( x) x mol/l mol /L g/ mol g/l More CuCl(s) will dissolve per litre of solutio. The solubilities are expressed correctly to 3 sigificat digits ad the aswer is reasoable. Uit 4 Part B MHR 319

5 126. The solubility of ickel(ii) phosphate, Ni 3 (PO 4 ) 2 (aq), is g/l. Determie the solubility-product costat for this solid. You eed to calculate the K sp for ickel(ii) phosphate, Ni 3 (PO 4 ) 2 (aq). You kow the solubility of Ni 3 (PO 4 ) 2 (aq) is g/l. Use the molar mass, M, of Ni 3 (PO 4 ) 2 ad m the formula to express the M solubility i mol/l. Write a balaced chemical equatio for the Determie the cocetratio of each io. 1 mol of Ni 3 (PO 4 ) 2 ioizes to give 3 mol of Ni 2+ (aq) ios ad 2 mol PO 3 4 (aq) ios. m M g /L g /mol mol/l Ni 3 (PO 4 ) 2 (s) 3Ni 2+ (aq) + 2PO 4 3 (aq) [Ni 2+ ] = 3[Ni 3 (PO 4 ) 2 ] = mol/l = mol/l [PO 4 3 ] = 2[Ni 3 (PO 4 ) 2 ] = mol/l = mol/l Write the expressio for the K sp. K sp = [Ni 2+ ] 3 [PO 4 3 ] 2 Substitute the io cocetratios ito the K sp expressio ad solve. K sp = [Ni 2+ ] 3 [PO 4 3 ] 2 = ( ) 3 ( ) 2 = The calculated value of K sp has the correct umber of sigificat digits that agrees with the give data. The small value for K sp is expected for a compoud of low solubility. 320 MHR Chemistry 12 Solutios Maual

6 127. The solubility of strotium fluoride, SrF 2 (aq), is 12.2 mg/100 ml. What is K sp for this solid? You eed to calculate the K sp for strotium fluoride, SrF 2 (s). You kow the solubility of strotium fluoride, SrF 2 (aq), is 12.2 mg/100 ml. Use the molar mass, M, of SrF 2 ad the m formula to express the solubility i M mol/l. Write a balaced equatio for the Determie the cocetratio of each io. Oe mol of SrF 2 ioizes to give oe mol of Sr 2+ (aq) io ad two mol F (aq) ios. Write the expressio for the K sp. Substitute the io cocetratios ito the K sp expressio ad solve. 1 g 12.2 mg 1000 mg 1 L 100 ml 1000 ml = g/l g /L molar solubility = g /mol = mol/l SrF 2 (s) Sr 2+ (aq) + 2F (aq) [Sr 2+ ] = [SrF 2 ] = mol/l [F ] = 2[SrF 2 ] = mol/l = mol/l K sp = [Sr 2+ ][F ] 2 = ( )( ) 2 = The calculated value of K sp has the correct umber of sigificat digits that agrees with the give data. The small value is expected for a compoud of low solubility. Uit 4 Part B MHR 321

7 128. Will a precipitate form if 1.00 ml of a mol/l silver itrate solutio, AgNO 3 (aq), is added to 1.00 L of a mol/l solutio of sodium chloride, NaCl(aq)? Show your calculatios. You eed to determie whether a precipitate will form. You kow that 1.00 ml of a mol/l silver itrate solutio, AgNO 3 (aq), is added to 1.00 L of a mol/l solutio of sodium chloride, NaCl(aq). The oly possible precipitate that ca form is silver chloride, AgCl(s). From Appedix B, you kow the K sp for silver chloride is Write the balaced equatio for the Use the formula cv to determie the amout i moles,, of Ag + (aq) ad Cl (aq) i the origial solutio. AgCl(s) Ag + (aq) + Cl (aq) + Ag cv mol/ L L mol Determie the total volume, V, after mixig the two solutios. Use the formula c to calculate the V molar cocetratios, c, of Ag + (aq) ad Cl (aq). Cl cv mol/ L 1.00 L mol V = 1.00 L ml = 1.00 L L = L Ag V L mol mol/l Cl V L mol mol/l 322 MHR Chemistry 12 Solutios Maual

8 Write the expressio for the K sp for AgCl. Q sp = [Ag + ][Cl ] Use the molar cocetratios calculated after mixig to determie a trial value Q sp. If Q sp > K sp, a precipitate of AgCl(s) forms. Q sp = [Ag + ][Cl ] = = K sp for AgCl is Q sp > K sp A precipitate will form. The calculatios seem reasoable ad the correct umber of sigificat digits has bee used. Uit 4 Part B MHR 323

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