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MCAT Chem > 9. Solutions > Flashcards

9. Solutions Flashcards

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1
Q

How do you know which substances are water-soluble?

A 
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
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2
Q

How do you know which substances are water-insoluble?

A

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

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3
Q

What is concentration? Units?

A

amount of solute dissolved in solvent; M (mol/L)

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4
Q

How to find percent composition by mass?

A

(mass of solute/mass of soln) * 100 (in g)

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5
Q

How to find mole fraction?

A

mole of target species/mole of all the species (in mol)

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6
Q

How to find molarity?

A

mol of solute/L of soln (M)

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7
Q

How to find molality?

A

mol of solute/kg of solvent (m)

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8
Q

Know M1V1 = M2V2

A

Oh research semester…

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9
Q

What is the best thing to do when solving any soln stoich?

A

Write out the balanced dissociation eqn

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10
Q

What is solvation/dissolution vs hydration vs mixture?

A

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

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11
Q

Know how to find Ksp (solubility product). Remember that Ksp is analogous to equil constant

A

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

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12
Q

What does high molar solubility mean?

A

more solute is dissolved; more ions = produced. Only temp can change solubility of solid solute

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13
Q

What if soln forms a precipitate?

A

Add H3O+ and form a mega aq eqn (H3O = react, water and H-base = product)

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14
Q

How to find new K if soln = dissolved in acid/base solns

A

K = Ksp x Kf

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15
Q

What is the common ion effect?

A

more common ions –> more likely to react w/ reactants –> more precipitate –> less solubility

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16
Q

Are slns homogeneous or heterogenous?

A

Homogenous (ie. Uniform appearance)

17
Q

Solns = based on enthalpy change. What are ideal solns?

A

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

18
Q

Dilute vs concentrated soln

A

Proportion of solute to solvent = small vs Proportion of solute to solvent = big

19
Q

Ksp expressions should never have denominators

A

Yeeee. Cuz you’re dissolving a pure solid into pure water

20
Q

Ion product (IP)

A

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

21
Q

Why do complex ions inc molar solubility?

A

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

22
Q

What happens to vapor pressure when more solute is added to solvent

A

Vapor pressure of solvent dec proportionately. You can find new vapor pressure using Raoult’s Law; then do final-initial for vapor pressure change

23
Q

Raoult’s Law

A

Know the formula. States that ideal sln behavior = observed when solute/solute, solute/solvent and solvent/solvent interactions are all very similar

24
Q

Osmotic pressure formula

A

PI = iMRT; osmotic pressure = colligative property

25
Q

How to change equil constants?

A

Change temp and/or identity of slns

26
Q

How to inc solubility of solid solutes? How to inc solubility of gases into sln?

A

Only temp can change solubility of solid solute. CHARGED CMPDS (as opposed to neutral cmpds) ARE MORE WATER-SOLUBLE
Gas solubility = directly proportional to pressure of sln and inv proportional to temp of sln

MCAT Chem (13 decks)

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