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Solubility Equilibrium (Ksp) Ksp Concept Overview

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  • Solubility Equilibrium (Ksp)

    Ksp Concept Overview

  • Solubility Equilibrium.092.notebook

    May 28:29 AM

    This is a saturated solution of PbCl2.

    Sketch the particulate diagram of the solution.Include relative sizes and numbers of ions and the interaction of water with at least one positive ion and one negative ion. Label each particle with its element symbol and charge, if necessary.

    Calculate the concentrations of Pb2+ and Cl- ions in solution at 25°C.

    Calculate the solubility of PbCl2 in grams in 1.5 L.

    1.

    2.

    3.

    Pb2+

    Cl-

    OHH

    http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s2_3.swf

  • Solubility Equilibrium Interactive Simulation

    Shaftesbury High School | 2240 Grant Ave., Winnipeg, MB | 204.888.5898 | www.pembinatrails.ca/shaftesbury

    Objectives

    1. To compare the solubility of various soluble ionic compounds.

    2. To examine the concentrations of various solutions at saturation.

    3. To compare Ksp values of soluble ionic compounds with Ksp values of ionic compounds with low

    solubility.

    Procedure

    1. Run the Concentration simulation at

    http://phet.colorado.edu/sims/html/concentration/latest/concentration_en.html. The

    following screen should appear.

    2. Familiarize yourself with the simulation by varying the type of solute, the amount of water, the

    rate of evaporation, etc…

    Data Collection and Calculations

    3. Calculate the molar mass of each compound and record the results in Table 1.

    4. Record the concentration at saturation of each solution in the table.

    http://phet.colorado.edu/sims/html/concentration/latest/concentration_en.html

  • Solubility Equilibrium Interactive Simulation

    Shaftesbury High School | 2240 Grant Ave., Winnipeg, MB | 204.888.5898 | www.pembinatrails.ca/shaftesbury

    5. Calculate the solubility of each solution in grams per litre. Show your calculations for one of the

    solutions below. They should follow a logical mathematical sequence, including proper units

    and significant figures.

    6. Calculate the solubility product constant, Ksp, of any solution with a 2:1 or 1:2 ratio of cation to

    anion. Show complete calculations in the space below, including proper units and significant

    figures.

    Table 1. Solubility Equilibrium Data for Eight Solutions of Ionic Compounds

    Substance Chemical Formula

    Molar Mass (g/mol)

    c at Saturation

    Solubility in g/L

    Ksp

    1. Drink Mix 2. Cobalt (II)

    Nitrate Co(NO3)2

    3. Cobalt (II) Chloride

    CoCl2

    4. Potassium Dichromate

    K2Cr2O7

    5. Potassium Chromate

    K2CrO4

    6. Nickel (II) Chloride

    NiCl2

    7. Copper (II) Sulfate

    CuSO4

    8. Potassium Permanganate

    KMnO4

    Questions

    6. How does the concentration of a saturated solution change as more solvent evaporates?

    7. Why are none of these solutions found in Ksp tables?

  • C8 Solubility Product Constants (AC J sp-

    Solubility Product Constants at 25°C

    Name

    barium carbonate

    barium chromate

    barium sulfate

    calcium carbonate

    calcium oxalate

    calcium phosphate

    calcium sulfate

    copperO] chloride

    copperO] iodide

    copperOO iodate

    copperOO sulfide

    ironOO hydroxide

    ironOO sulfide

    ironCIII) hydroxide

    leadOO bromide

    leadOD chloride

    leadOD iodate

    leadOD iodide

    lead00 sulfate

    magnesium carbonate

    magnesium fluoride

    magnesium hydroxide

    mercuryO) chloride

    silver bromate

    silver bromide

    silver carbonate

    silver chloride

    silver chromate

    silver iodate

    silver iodide

    strontium carbonate

    strontium fluoride

    strontium sulfate

    zinc hydroxide

    zinc sulfide

    Formula

    BaC03f3)

    BaCr04(s)

    BaSO^cs)

    CaC03f33

    CaC204fs); CaOOCCOOfs)

    Ca3(P0^2is)

    CaS04(33

    CuCI(33

    Culfs)

    cuao332Cs)

    CuS(33

    FeC0H)2Cs)

    FeS(33

    FeCOH33C33

    PbBr2(33

    PbCl2(s)

    Pba0332(s)

    Pbl2Cs)

    PbSOz,cs)

    MgC03f33

    MgFacs)

    MgC0H)2Cs)

    Hg2Ci2(s)

    AgBr03f33

    AgBr(33

    Ag2C03Cs3

    AgCI(3)

    Ag2Cr04(3)

    Agi03cs3

    Agi(s3

    SrC03C33

    SrF2(3)

    SrS04C33

    ZnCOH32(33

    ZnSt33

    'fsp

    2.6 X 10^^

    1.2 X 10^1°

    1.1 X 10^1°

    5.0 X 10"^

    2.3 X 10"^

    2.1 X 10~33

    7.1 X 10-5

    1.7 X 10"^

    1.3 X 10^12

    6.9 X 10"^

    6.0 X 10-3^

    4.9 X 10^^^

    6.0 X 10"^^

    2.6 X 10^33

    6.6 X 10"^

    1.2 X 10^5

    3.7 X 10-^^3

    8.5 X 10-9

    1.8 X 10-«

    6.8 X 10"̂ ^

    6.4 X 10-9

    5.6 X 10-12

    1.5 X 10-1^

    5.3 X 10-5

    5.4 X 10-13

    8.5 X 10-12

    1.8 X 10-1°

    1.1 X 10-12

    3.2 X 10-^

    8.5 X 10-1^

    5.6 X 10-10

    4.3 X 10-9

    3.4 X 10"^

    7.7 X 10-1^

    2.0 X 10-25

    Values in this table are taken from The Physics, 76th Edition.

    CRC Handbool< of Chemistry and

    802 Appendix C

  • Negative Ions

    Essentially All

    Essentially All

    Essentially All

    Nitrate, NO3

    Acetate, CH3COO

    Chloride, Cl Bromide, Br Iodide, 1

    Sulfate, so/

    Sulfide, Ŝ

    Hydroxide, OH

    Phosphate, P04^ Carbonate, COB^

    Sulfite, SOB^

    Chromate, Cr04^

    Solubility Chart

    Positive Ions

    Alkali ions (U\ Na% K\ Rb", Cs")

    Hydrogen ion, H*

    Ammonium ion, NH4*

    Essentially All

    Essentially All, EXCEPT Ag"

    Ag% Pb'^ Hg2'% Cu\ TV

    All others

    Câ % Sr̂ % Ba^^ Pb2% Ra "̂

    All others Alkali ions and H\ HH/, Be^\ Mg^', Ca^",

    Sr̂ % Ba2% Râ *

    All others

    Alkali ions and H\ HH/, Sr̂ ", Ba'% Ra'% Tl '

    All others

    Alkali ions and H\ NH4'

    All others

    Bâ % Sr2^ Pb̂ % Ag'

    All others

    Solubility

    Soluble, (aq)

    Soluble, (aq)

    Soluble, (aq)

    Soluble, (aq)

    Soluble, (aq)

    Low Solubility, (s)

    Soluble, (aq) Low Solubility,

    (s) Soluble, (aq)

    Soluble, (aq)

    Low Solubility, (s)

    Soluble, (aq) Low Solubility,

    (s) Soluble, (aq)

    Low Solubility, (s)

    Low Solubility, (s)

    Soluble, (aq)

  • Calculate the solubility in grams per litre of gypsum, formula

    CaS04, given a Ksp of 7.1 x 1 0"^ at 25°C.

    Calculating Solubility

  • Calculate the solubility of strontium f luoride in mg in 200 . mL of

    solution. Check C8 for Ksp at 25°C.

    Calculating Solubility 2

  • Calculate the solubility product constant, Ksp, for silver sulfate if

    1 5 mg dissolves to make a saturated solution in 1 00 . mL at 25°

    C.

    Calculating Ksp

  • Steps to calculate Ksp from solubility.

    © S I . Wr i te balanced equilibrium equation.

    © S2. Wr i te Ksp expression

    © S3. Calculate moles of solid.

    © S4. Determine moles of ions.

    © S 5 . Substitute all values into Ksp expression.

    Calculate Ksp of magnesium fluoride at 25°C given that

    0 .00172 g dissolves in 1 00 . mL of solution.

    Summary of How to Calculate Ksp

  • Common ion Effect

    The common ion effect is an example of Le Chatelier's

    principle that applies to solubility equilibrium

    By adding a common ion to a sparingly soluble substance, the

    solubility of that substance actually changes.

    Since you can't simply add an ion, an entire solution containing the

    common ion must be added to the sparingly soluble solution.

    Intro to Common Ion Effect

  • Common Ion Questions

    Calculate the molar solubility of iron (II) hydroxide in pure

    water at 25°C. Ksp is 4.9 x l 0'^^.

    Convert the solubility to mg in 450. mL of solution.

    Calculate the mass of iron (III) hydroxide that dissoves in mg in

    450. mL of solution with 0.10 M sodium hydroxide solution.

    By what proportion did the solubility change?

    ^

    Common Ion Sample Question 1

  • Common Ion Questions

    The solubility of a saturated solution changes if you add an amount

    of a second solution containing a commmon ion, NOT the Ksp.

    Calculate the solubility in mg in 200 mL of saturated iron (II) sulfide

    solution in pure water:

    a) in pure water.

    b) in a solution containing 0.1 0 M sodium sulfide.

    ^

    p.492 Q.9 b)

    Common Ion Sample Problem 2

  • W o w ! The solubility of a sparingly soluble ionic salt decreases

    when you add a solution containing a common ion. In this case,

    it has decreased by a factor of 1 O V 0'^^ = ] 00 0 0 0 000 !

    This is simply a quantitative application of Le Chatelier's

    Principle.

    Common Ion Effect Conclusion

  • Predicting Precipitation p. 489 Q.5 a)

    Wi l l a precipitate form from the mixing of 25.0 mL of

    0.010 mol/L of silver nitrate and 25.0 mL of 0.0050 mol/L

    potassium chloride? Get Ksp values from p.802

    ^

    Predicting Precipitation Sample Problem 1

  • C "̂ -D f\^ C '^ Predicting Precipitation

    Wil l a precipitate form if 20 mL of 0.0001 M lead (II) nitrate

    solution is combined with 15 mL of 0.001 M calcium hydroxide

    Step 1. Write balanced equilibrium dissociation equation for the

    precipitate using solubility rules.

    solution? 1/ _ , - - ' o " ^

    > = >

    Predicting Precipitation Sample Problem 2

  • How to Solve Predicting Precipitation Questions

    Step 1. Wr i te the two balanced dissociation equations (DIE)

    Step 2. Predict the precipitate that forms and write the

    balanced solubility equilibrium equation, and Ksp

    expression.

    Step 3. Calculate the moles of each ion in the equilibrium equation and divide them by the total volume of solution

    to obtain concentrations.

    Step 4 . Plug concentrations into Ksp expression to get Q.

    Step 5. Compare Q value to Ksp value and determine which direction is favoured and whether a precipitate forms.

    p.489 Q.5 a) & 5b)

    Summary of Predicting Precipitation

  • Chemistry 40S Problem Set: Solubility Equilibrium

    1. Calculate the Ksp of iron (III) hydroxide if 1.60 x 10-6 mg dissolves in 150 mL of solution. (2)

    2. A. Calculate the solubility in mg of calcium phosphate in 200 mL of pure water. Use

    tables for Ksp. (2) B. Calculate the solubility in mg of calcium phosphate after 0.20 M of sodium

    phosphate is added to 200 mL of solution. (2) C. What happens to the solubility of an ionic compound with the addition of a

    common ion? (1)

    3. Will a precipitate form if 15 mL of 0.15 M Pb(NO3)2 is mixed with 100. mL of 0.10 M

    NaI? Show all of your work for full marks. (3)

    /10

  • Chemistry 40S/40SH Lab Practicum

    Student:________________ Student:__________________ Student:_________________

    OBJECTIVE

    In groups determined by the instructor design and conduct an experiment to …

    Determine the Ksp of a saturated solution of PbCl2 using 100.0 mL of saturated PbCl2(aq) and 20.0 mL of 0.50 M K2CrO4(aq).

    TIMELINE

    Day 1: Student groups collaborate and submit one copy of each of the following to the instructor for grading:

    1. A stepwise description of the complete laboratory procedure, including sketches. Sketches must be labelled and embedded in the procedure.

    2. An outline of the stepwise sequence of calculations that must be performed to arrive at the

    intended result, including balanced equations, the Ksp expression, and units. Use Ksp calculations from Ksp of PbCl2 prelab to develop the sequence.

    Day 2: Students perform and complete the lab according to their procedure and submit their results for grading.

    CHEMICALS & EQUIPMENT

    The following equipment may be used to fulfil the lab objective. Other materials may be sanctioned by the instructor upon request by student groups.

    safety goggles distilled water

    wash bottle 50 & 100 mL

    graduated cylinders Glass stir rod

    massed & folded filter paper

    Plastic funnel 50 & 250 mL

    beakers Funnel clamp &

    stand

  • Chemistry 40S/40SH Lab Practicum

    Student:________________ Student:__________________ Student:_________________

    Lab Practicum Assessment Rubric

    Criteria Developing

    (0 — 1 mark) Intermediate

    (2 marks) At Level

    (3 marks)

    Procedure

    Procedure is missing significant information such that a high level of

    intuition or experience in chemistry is necessary to interpret the information and successfully conduct

    the experiment (1) or there is no chance that the

    procedure is useful enough to attain the objective (0)

    Aspects of the procedure (including labeled sketches)

    are missing, out of sequence, or incorrect but

    procedure is complete enough that it is likely a

    skilled chemistry student could still conduct the

    experiment; accuracy of results may be compromised

    Procedure follows a logical sequence, includes labeled sketch(es) of the

    laboratory setup, and is complete to the

    extent that any chemistry student may

    successfully conduct the experiment

    Calculations

    Results contain less than Intermediate level

    assessment criteria (1) or no calculations presented

    (0)

    Calculations are communicated, but some

    aspect is incomplete, incorrect, or otherwise

    unclear

    All required calculations are clearly

    listed in a logical sequence, including

    correct balanced equations, the Ksp

    expression, and units

    Results

    Results are not submitted (0) or are incorrect to the

    extent that a final Ksp value is not calculated (1)

    Sequencing of calculations is incomplete or incorrect.

    Complete and correctly calculated results are submitted following

    the sequence of calculations developed

    on Day 1

    Student Collaboration & Efficiency

    Less than intermediate criteria

    the student’s contribution was less than an equitable portion of the total group’s collaboration or the student

    collaborated with little consideration to efficiency

    The student contributed equitably

    to the group objectives, assuming

    and completing a critical role in an

    efficient manner over the entire two days

    /12

  • Ksp of PbCb Prelab

    If 1.00 g of solid lead (II) chromate precipitates, calculate the

    Ksp of PbCb.

  • Chemistry 40S Solubility Equilibrium Practice Quiz

    Particulate Diagram

    Saturated Solution of Ca(OH)2 at 25°C

    1. In the flask to the left, sketch a particulate diagram of each of the components in solution, including water molecules. Pay attention to relative size and number of each ion. Show the interaction of water molecules with at least one positive ion and one negative ion. Each particle should be labelled with the appropriate element symbol and ion charge. (2)

    Useful resource: http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s2_3.swf

    Interpreting Ksp Values

    2. Which saturated solution in equiliibrium has the greatest solubility at 25°C? (1)

    A. Barium chromate B. Silver carbonate C. Zinc hydroxide D. Copper (I) iodide 3. Which compound has the lowest concentration of ions in solution at 25°C? (1)

    A. BaCrO4 B. Mg(OH)2 C. CuCl D. SrSO4

    http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s2_3.swfhttp://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s2_3.swfhttp://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s2_3.swf

  • Chemistry 40S Solubility Equilibrium Practice Quiz

    Solubility from Ksp data (molar solubility & other units—mg, g/L, etc…)

    4. Calculate the molar solubility in mol/L of silver bromate at 25°C. (2)

    5. Calculate the solubility of 500.0 mL of a saturated solution of ZnS at 25°C in milligrams. (3)

    Ksp from solubility data

    6. Calculate the solubility product constant, Ksp, of Bi2S3 at 25°C if its molar solubility is 1.0 x 10–15

    mol/L. (2) (Zumdahl, 2000, p.760)

    Common ion effect

    7. Calculate the molar solubility of solid CaF2 (Ksp = 4.0 x 10–11) in a 0.025 M NaF solution at 25°C. (2)

    (Zumdahl, 2000, p.764)

  • Chemistry 40S Solubility Equilibrium Practice Quiz

    Predicting Precipitation (comparing Q to Ksp)

    8. Will a precipitate form when 750.0 mL of 0.0040 M Ce(NO3)3 is added to 300.0 mL of 0.020 M KIO3? Ksp of the insoluble precipitate is 1.9 x 10–10. (3) (Zumdahl, 2000, p.766)

    /16