Solubility Equilibrium

Solutions Solvent – Solute – Molecular Solution – Organics – Non-metal/non-metal –

Ionic Solutions (Electrolytes) – Ionic – Acids – Bases –

Electrolytes Ions are attracted to electrodes

CuI IBr CO 2 H 2 SO 4 SF 6 Al(OH) 3 SnO 2 CH 3 COOH NH 3 Al 2 (SO 3 ) 3 O 2 Types of Solutes (solutions)

CuI (s) ↔ Cu + (aq) + I - (aq) IBr (g) ↔ IBr (aq) CO 2(g) ↔ CO 2(aq) H 2 SO 4 ↔ 2H + (aq) + SO 4 2- (aq) SF 6(s) ↔ SF 6(aq) Al(OH) 3(s) ↔ Al 3+ (aq) + 3OH - (aq) SnO 2(S) ↔ Sn 4+ (aq) + 2O 2- (aq) CH 3 COOH (l) ↔ CH 3 COO - (aq) + H + (aq) NH 3(g) ↔ NH 4 + (aq) + OH - (aq) Al 2 (SO 3 ) 3(s) ↔ 2Al 3+ (aq) + 3SO 3 2- (aq) O 2(g) ↔ O 2(aq) Dissociation Equations

Solubility The extent to which a solute is soluble in water at a given temperature. Many types of units. Moles solute L solution Grams solute 100.mL solution %Volume solute Volume solution %Mass solute Mass solution Moles solute kg solvent Moles + charge L solution

Saturated Solutions A solution is saturated when the maximum amount (concentration) of solute is dissolved in the solvent at a given temperature. Solubility equilibrium (Saturation) exists when the rate of dissolving = rate of crystallization Some solid must be present.

Dissociation Equations Al 2 (SO 3 ) 3(s) ↔ 2Al 3+ (aq) + 3SO 3 2- (aq) Forward is dissociation Reverse is precipitation Both occurring at same rate  Saturated

6.02x x

Solubility and Ion Concentration If 250.mL of saturated NaF solution was evaporated to dryness and found to contain 3.59g NaF. What is the molar solubility?

The molar solubility of MgCO 3 is 1.26x10 -3 M. What is this in g/100.0mL.

Solubility Curves Which salt is most soluble at 20˚C? If you put 50g KNO 3 in 100g water at 20˚C and heat it, what happens? Is the dissolution of Ce 2 (SO 4 ) 3 endo- or exothermic?

Work on Questions… Practice 1abcdef, 2ab, 3a, 4, 8, 11, 13, 14, 16, 17. Assignment handouts #1 and 2

Al 2 (SO 3 ) 3(s) ↔ 2Al 3+ (aq) + 3SO 3 2- (aq) 2.4mol of Al 2 (SO 3 ) 3(s) is dissolved and diluted to a volume of 1.0L. What are the ion concentrations?

What are the ion concentrations in a solution containing 0.26g Ca(OH) 2 in 500.0mL of solution? Hoop#1 Dissociation Equation

Dilution If 25.0mL of 0.010M Br - is added to 15.0mL of 0.13M Cl -, what is the resulting concentration of each ion?

What are the concentrations of all ions present when 2.5mL of 0.85M MgCl 2 is added to 8.0mL of 0.55M AlBr 3 ?

What are the concentrations of all ions present when 15mL of 0.80M MgCl 2 is added to 80.0mL of 0.35M AlCl 3 ?

Work on Questions… 18c, 20df.

Predicting Solubility

Is PbI 2 expected to precipitate? Would a ppt form if equal volumes of 0.20M KI and Pb(NO 3 ) 2 are mixed? Would a ppt form if equal volumes of 0.20M AgNO 3 and Li 2 S are mixed?

Double Replacement Rxns Formula Equations – include all species and (aq) or (s) designations (no ions shown). 2AgNO 3(aq) + Na 2 CO 3(aq) → Ag 2 CO 3(s) + 2NaNO 3(aq) Complete Ionic Equations – show (aq) species as separate ions. 2Ag + (aq) + 2NO 3 - (aq) + 2Na + (aq) + CO 3 2- (aq) → Ag 2 CO 3(s) + 2Na + (aq) + 2NO 3 - (aq)

Net Ionic Equations Do not show any spectator ions, only those involved in precipitation. 2Ag + (aq) + 2NO 3 - (aq) + 2Na + (aq) + CO 3 2- (aq) → Ag 2 CO 3(s) + 2Na + (aq) + 2NO 3 - (aq) 2Ag + (aq) + CO 3 2- (aq) → Ag 2 CO 3(s)

Work on Questions… Practice 21efghij, 22, 24abc, 25hij. Assignment handout #3

Selective Ion Precipitation A qualitative method to determine whether certain ions are present in a solution or not. Let’s assume a sample Ag + and Sr 2+. We would have to ppt one at a time, not both. Cl - SO 4 2- S 2- OH - PO 4 3-

Ag + Sr 2+ Salt Cl - SO 4 2- S 2- OH - PO 4 3- Ag + Sr 2+ The anion being added must be added as a soluble salt. Otherwise, there’s no way to add it (there’s no such thing as a lone ion, except in plasma). Step 1: Add ___________ to precipitate ___________ Step 2: Filter to remove any ________ that forms Step 3: Add ___________ to precipitate ___________ Step 4: Filter to remove any ________ that forms

How would you analyse a solution that may, or may not, contain Ag +, Ba 2+, and Ni 2+ ? Cl - SO 4 2- S 2- OH - PO 4 3- Step 1: Add ___________ to precipitate ___________ Filter to remove any ________ that forms Step 2: Add ___________ to precipitate ___________ Filter to remove any ________ that forms Step 3: Add ___________ to precipitate ___________ Filter to remove any ________ that forms Step 4: Add ___________ to precipitate ___________ Filter to remove any ________ that forms

Work on Questions… 26, 30, 32, 35, 37.