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Flashcards in ch 9 - Solutions Deck (47)
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1

solutions

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

2

solute

dissolved or dispersed in a solvent

3

solvent

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

4

Solvation

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

5

when solvation is exothermic

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

6

when solvation is endothermic

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

7

ideal solution

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

8

entropy of dissolution

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

9

solubility of a substance

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

10

saturated solution

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

11

if more solute is added to an already saturated solution

solute will not dissolve but precipitate to the bottom

12

dilute solution

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

13

concentrated solution

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

14

when is a solute considered soluble

when Gibbs free energy is negative and reaction will proceed spontaneously

15

sparingly soluble salts

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

16

aqueous solution

solvent is water

17

hydronium ion

H3O+

18

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

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

19

complex ion - or coordination compound

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]

20

ligands

electron pair donor molecules

21

coordinate covalent bonds

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

22

chelation

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

23

concentration

denotes the amount of solute dissolved in a solvent

24

percent composition by mass

mass of solute/mass of solution x 100

25

mole fraction (X)

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

26

molarity (M)

M = moles of solute/liters of solution

27

molality (m)

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

28

normality (N)

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

29

equation for concentration of solution after dilution

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

30

saturation point

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