9. Solutions Flashcards
How do you know which substances are water-soluble?
all salts in Group 1; all salts containing ammonium, nitrate and acetate; all halides except F unless they're reacting with Ag, Pb or Hg; all salts with sulfate unless they're reacting with Ca, Sr, Ba, Pb CHARGED CMPDS (as opposed to neutral cmpds) ARE MORE WATER-SOLUBLE
How do you know which substances are water-insoluble?
all metal oxides unless they’re reacting with Group 1 salts and ammonium; all hydroxides unless they’re reacting with Group 1 salts, ammonium, Ca, Sr, Ba; all carbonates, sulfides, sulfites and phosphates unless they’re reacting with Group 1 salts, ammonium
What is concentration? Units?
amount of solute dissolved in solvent; M (mol/L)
How to find percent composition by mass?
(mass of solute/mass of soln) * 100 (in g)
How to find mole fraction?
mole of target species/mole of all the species (in mol)
How to find molarity?
mol of solute/L of soln (M)
How to find molality?
mol of solute/kg of solvent (m)
Know M1V1 = M2V2
Oh research semester…
What is the best thing to do when solving any soln stoich?
Write out the balanced dissociation eqn
What is solvation/dissolution vs hydration vs mixture?
Electrostatic attraction b/w solute and solvent: break intermolecular bonds b/w solute and those of solvent —> then form new intermolecular bonds b/w solute and solvent molec vs when water is the solvent of the sln vs when gas dissolves in gas
Know how to find Ksp (solubility product). Remember that Ksp is analogous to equil constant
Write out balanced aq eqn for soln –> make ICE table (solids and liquids are negligible, conc only matters w/ aq state) –> Ksp = [products]/[reactants] (exponents in Ksp = coefficients in eqn) –> solve it like algebra
What does high molar solubility mean?
more solute is dissolved; more ions = produced. Only temp can change solubility of solid solute
What if soln forms a precipitate?
Add H3O+ and form a mega aq eqn (H3O = react, water and H-base = product)
How to find new K if soln = dissolved in acid/base solns
K = Ksp x Kf
What is the common ion effect?
more common ions –> more likely to react w/ reactants –> more precipitate –> less solubility
Are slns homogeneous or heterogenous?
Homogenous (ie. Uniform appearance)
Solns = based on enthalpy change. What are ideal solns?
When enthalpy change is zero: overall strength to make new bonds is equal to overall strength of breaking old bonds. Ideal sln = determined by Raoult’s Law
Dilute vs concentrated soln
Proportion of solute to solvent = small vs Proportion of solute to solvent = big
Ksp expressions should never have denominators
Yeeee. Cuz you’re dissolving a pure solid into pure water
Ion product (IP)
Analogous to Q: helps determine the progress of a rxn
IP unsaturated sln, will dissolve more
IP=Keq —> equil, saturated
IP>Keq —> supersaturated sln, will precipitate
Why do complex ions inc molar solubility?
Complex ions have multiple pole bonds b/w ligands and central atom —> lots of dipole-dipole interaction —> stabilizes dissolution of complex ion. They also have coordinate covalent bonding
What happens to vapor pressure when more solute is added to solvent
Vapor pressure of solvent dec proportionately. You can find new vapor pressure using Raoult’s Law; then do final-initial for vapor pressure change
Raoult’s Law
Know the formula. States that ideal sln behavior = observed when solute/solute, solute/solvent and solvent/solvent interactions are all very similar
Osmotic pressure formula
PI = iMRT; osmotic pressure = colligative property
