ch 9 - Solutions

Question 1

solutions

Answer 1

homogeneous throughout - same phase. All of them are mixtures but not all mixtures are solutions

Question 2

solute

Answer 2

dissolved or dispersed in a solvent

Question 3

solvent

Answer 3

component of solution that remains in the same phase after mixing, in which solute is dissolved; if already in same phase as solute, the solvent is that which is present in greater quantity

Question 4

Solvation

Answer 4

the electrostatic interaction between solute and solvent molecules; also called dissolution; when water is solvent called hydration

Question 5

when solvation is exothermic

Answer 5

when new interactions between molecules are stronger than the original ones; favored at low temps

Question 6

when solvation is endothermic

Answer 6

when the new interactions formed are weaker than the original ones; favored at high temps; most dissolutions are this

Question 7

ideal solution

Answer 7

enthalpy of dissolution is equal to zero; solutions get close to this when overall strength of new interactions is approximately equal to overall strength of original interactions

Question 8

entropy of dissolution

Answer 8

second property (along with enthalpy) that contributes to whether a dissolution is spontaneous or not - at constant temp and pressure, entropy always increases upon dissolution

Question 9

solubility of a substance

Answer 9

the max amount of that substance that can be dissolved in a particular solvent at a given temp

Question 10

saturated solution

Answer 10

when the max amount of solute has been added and the dissolved solute is in equilibrium with its undissolved state

Question 11

if more solute is added to an already saturated solution

Answer 11

solute will not dissolve but precipitate to the bottom

Question 12

dilute solution

Answer 12

solution in which proportion of solute to solvent is small ; still unsaturated

Question 13

concentrated solution

Answer 13

solution in which proportion of solute to solvent is large; still unsaturated

Question 14

when is a solute considered soluble

Answer 14

when Gibbs free energy is negative and reaction will proceed spontaneously

Question 15

sparingly soluble salts

Answer 15

those solutes that dissolve minimally in a solvent (molar solubility under 0.1 M)

Question 16

aqueous solution

Answer 16

solvent is water

Question 17

hydronium ion

Answer 17

H3O+

Question 18

solubility rules for aqueous solutions (know rules one and two)

Answer 18

1. All salts containing ammonium (NH4)+ and alkali metal (group 1) cations are water-soluble; 2. all salts containing nitrate (NO3)- and acetate (CH3COO-) anions are water-soluble; 3. Halides (Cl-, Br-, I-) except fluorides, are water soluble except those formed with Ag+, Pb2+, and (Hg2)2+; 4. All salts of sulfate ion (SO4)2- are water soluble, except those formed with Ca2+, Sr2+, Ba2+, and Pb2+; 5. all metal oxides are insoluble except ones formed with alkali metals, ammonium, and CaO, SrO, and BaO; 6. all hydroxides are insoluble except ones formed with alkali metals, ammonium, and Ca2+, Sr2+, and Ba2+; 7. all carbonates (CO3)2+, phosphates (PO4)3-, sulfides S2-, and sulfites (SO3)2- are insoluble except ones formed with alkali metals and ammonium

Question 19

complex ion - or coordination compound

Answer 19

refers to a molecule in which a cation is bonded to at least one electron pair donor (which could include the water molecule) [complexation reactions]

Question 20

ligands

Answer 20

electron pair donor molecules

Question 21

coordinate covalent bonds

Answer 21

bonds that hold complexes together, in which an electron pair donor (a Lewis base) and an electron pair acceptor (a Lewis acid) form very stable Lewis acid-base adducts

Question 22

chelation

Answer 22

central cation of a complex is bonded to the same ligand in multiple places; usually requires large organic ligands that can double back to form second or third bond with the central cation

Question 23

concentration

Answer 23

denotes the amount of solute dissolved in a solvent

Question 24

percent composition by mass

Answer 24

mass of solute/mass of solution x 100

Question 25

mole fraction (X)

Answer 25

XsubA = moles of A/total moles of all species; used to calculate the vapor pressure depression of a solution

Question 26

molarity (M)

Answer 26

M = moles of solute/liters of solution

Question 27

molality (m)

Answer 27

m = moles of solute/kilograms of solvent; for dilute aqueous solutions at 25 degrees C, the molality is approx equal to molarity because the density of water at this temp is 1 kg per L. situations where it is required are boiling point elevation and freezing point depression

Question 28

normality (N)

Answer 28

equal to the number of equivalents of interest per liter of solution; equivalent is measure of the reactive capacity of a molecule (equal to a mole of the species of interest); how many moles of electrons an ion will accept in a certain solution

Question 29

equation for concentration of solution after dilution

Answer 29

M sub i (V sub i) = M sub f (V sub f); M = molarity, V = volume and subscripts i and f = initial and final values

Question 30

saturation point

Answer 30

in process of creating a solution, this is the equilibrium, where the solute concentration is at its max value for the given temp and pressure; rates of dissolution and precipitation are equal, and concentration of dissolved solute reaches a steady state (constant) value; neither is favored thermodynamically

Question 31

reaction example that represents dissociation of such a solute in solution

Answer 31

A sub m (B sub m) ->

Question 32

solubility product constant (K sub sp) for example formula A sub m B sub n

Answer 32

K sub sp = [A^(n+)]^m[B^(m-)]^n; where concentrations of ionic constituents are equilibrium (saturation) concentrations

Question 33

Ion product (IP)

Answer 33

used to determine where the system is with respect to the equilibrium position; analogous to the reaction quotient, Q, for other chemical reactions: IP = [A^(n+)]^m[B^(m-)]^n; concentrations used here are the ionic constituents at that given moment in time, which may differ from equilibrium concentration

Question 34

unsaturated solution

Answer 34

if a salt’s IP is less than the salt’s Ksp; dissolution is thermodynamically favored over precipitation

Question 35

supersaturated solution

Answer 35

IP is greater than Ksp, solution is beyond equilibrium; thermodynamically unstable and any addition or further cooling will cause spontaneous precipitation (achieved by dissolving more solute and then cooling solution)

Question 36

molar solubility

Answer 36

molarity of a solute in a saturated solution

Question 37

common ion effect

Answer 37

the reduction in molar solubility that occurs to solubility of salt when it is dissolved in a solution that already contains one of its constituent ions

Question 38

colligative properties

Answer 38

physical properties of solutions that are dependent on the concentration of dissolved particles but not on the chemical identity of the dissolved particles: vapor pressure depression, boiling point elevation, freezing point depression, osmotic pressure

Question 39

Raoult’s law

Answer 39

accounts for vapor pressure depression caused by solutes in solution; as solute is added to a solvent, vapor pressure of the solvent decreases proportionately: P sub A = X sub A x P, degree sign, sub A; P sub A = vapor pressure of solvent A when solutes are present; X sub A = mole fraction of the solvent A in the solution; P, degree sign, sub A = vapor pressure of solvent A in its pure state

Question 40

formula for which the boiling point of a solution is raised relative to that of the pure solvent

Answer 40

delta T sub b = iK sub b (m); delta T sub b = increase in boiling point; i = van’t Hoff factor; K sub b = proportionality constant characteristic of a particular solvent; m = molality of the solution

Question 41

boiling point

Answer 41

temperature at which the vapor pressure of the liquid equals the ambient (incident) pressure; higher in solutions than pure solvents

Question 42

Van’t Hoff factor

Answer 42

corresponds to the number of particles into which a compound dissociates in solution

Question 43

causes of freezing point depression

Answer 43

presence of solute particles interferes with formation of lattice arrangement of solvent molecules associated with the solid state causing a need for a greater amount of energy to

Question 44

formula for freezing point depression

Answer 44

delta T sub f = i(K sub f)m; delta T sub f = freezing point depression; i = van’t Hoff factor; K sub f = proportionality constant characteristic of a particular solvent; m = molality of solution

Question 45

osmotic pressure

Answer 45

refers to a “sucking” pressure generated by solutions in which water is drawn into a solution: pi symbol = iMRT; where pi = osmotic pressure; i = van’t Hoff’s factor; M = molarity of the solution; R = ideal gas constant; T = temp

Question 46

boiling point of water

Answer 46

100 C; 212 F, 273.2 K

Question 47

ideal solutions

Answer 47

solutions that obey Raoult’s law which holds only when the attraction between the molecules of the different components of the mixture is equal to the attraction between the molecules of any one component in its pure state.