Chapter 17 Solutions Flashcards
Dalton’s Law of partial pressures
The P total is the sum of all partial pressures
Ptot= Pgas1 + Pgas 2 + Pgas3…
A solution has two components.
A solute (lesser) A solvent (greater)
Solutions Examples (Solute and Solvent)
Humidity - Gas - Gas
Rain - Liquid - Gas
snow - Solid - Gas
Carbonated Drinks, Sodas - gas -Liquid
Gin and Tonic - Liquid - Liquid
Salt Water, Solutions in lab- Solid -Liquid
Solution concentration
Molar (M)= amount of solute (moles)/ volume of solution (liters)
Percents (Formulas)
Mass percent:
(mass of solute/mass of solution) x 100
Volume percent:
(volume of solute/volume of solution) x 100) Volume is based on the initial volumes.
Mass Volume percent
(mass of solute(grams)/ volume of solution(mL)) x 100
Parts per Unit
a. Part per million:
1ppm= 1mg/L = 1g solute/ 1 x10^6g solution
b. Part per billion
1ppb = 1 ug/L = 1g /10^9 solution
c. Part per trillion
1ppt = 1ng/L = 1g/ 10^12 g solution
Mole Fraction (xi) and Percent
Mole percent xi (100)
xi = moles of i/ (total solution moles)
where xi +xj + xk+… =1.00
mole percent = 100xi
Molality(m)
amount of solute (moles)/ mass of solvent (kg)
Molality and Molarity are equal for dilute solutions where water is the solvent
Solution density is that of water (1g/mL)
(1L solution) (1000mL/L) (1g/mL) (kg/1000g) = 1kg solution
Normality (N)
the molarity multiplied by the number of equivalents. Used with acids( H+), bases (OH-), redox and precipitation
Normality (N) = ( # of equivalents) (Molarity)
Solubility
amount of solute that can be dissolved in a solvent.
Solubility = grams of solute dissolved/ given mass or volume of solvent
Molar Solubility
units are moles of solute per liter of solution
M soln = M solute + M solvent
Volume formula
Sometimes they are additive unless there is stated volume change or density change
V soln = V solute + V solvent
Polar molecules
Asymmetric molecules
Water, ionic compounds, salts, Alcohol, Water-Soluble Compounds, Hydrophillic
Non-polar molecules
Symmetric molecules
- Hydrocarbons
Molecular compounds
Oils, etc.
Like dissolves like idea
When polar molecules interact with other polar molecules, and non-polar molecules interact with other non-polar molecules they dissolve each other.
Enthalpy of solution
Enthalpy solution > 0 is endothermic
Enthalpy of solution < 0 is exothermic
Factors that contribute to enthalpy of solution
Breaking the solute into individual components, called expanding the solute endothermic
- Overcoming intermolecular forces in solvent to make room for the solute called expanding the solvent. (H2) endothermic
- Allowing the solute and the solvent to interact to form a solution (H3) exothermic
H soln = H1 + H2 + H3
Ideal solution
Change in enthalpy = 0
Possible combinations:
Solutes and Solvents:
Polar = Enthalpy large > 0
Non-polar with Enthalpy is small. < 0
When all values are small or Large they cancel each other out or dissolve and become small.
A mixture of both small and large: Total enthalpy = Large
Total Enthalpy small = solution forms
Total Enthalpy Large = no solution forms
Solution formation and equilibrium
Dissolving process will occur until equilibrium is reached
Solute + Solvent = Solution
Solubility (increases with temp except sulfates and phosphates).
Saturated
Saturated line represents the point where the dissolution and crystallization are both occuring and in equilibirum wiht each other
Undersaturated
Region on the graph below the saturated line when the solven cen dissolve more solute than available.
Supersaturated
Region on the graph occurs when the solution has more solute in solution than equlibrium allows.
Scenario = unstable and cause excess solute to crystalize
Fractional Crystallization
Solubulity to seperate solute.
Ex: Impure solid with mostly A and some B. Dissolve solide in high
temp then cool solution and each A and B will crystalize at different times.
Structure effects
Structure is affected extremely by solubility:
Fat soluble compound are non-polar
Water-soluble compounds are polar
What are Fat soluble compounds composed of?
Mostly C and H atoms and possibly on e OH group
What are water-soluble compund composed of
Mostly OH groups (polar) along with C and H atoms
Temp effects
- Soldis dissolved in liquids = solubility increases as temp increaese
- gases dissolved in liquids = the solubility of a gas in a liquid decrease as temperature increases.
Reason is because the increase temp increases the kinetic energy of the gas causing the gas to escape the solution
Pressure effects (For gases dissolved in liquid
As pressure increases the solubility of a gas in a liquid increase
Henry’s Law
C is solubility or concentration. K is Henry’s law constant.
Pgas = pressure of gas
Formula examples
C= k Pgas
k = C1/P1 = C2/P2
C= mol/L
Raoult’s Law
Partial pressure (Pa) = to the mole fraction (xa) multiplied by the pure pressure of solvent (PA o)
Pa = xa PoA
Pb = xbPbO
Xa +Xb =1.00
Ptot = Pa+ PB
Ptot = xA PA^o + xbPB^o
PA = xAPtot
novolatile
Does not have an appreciable vapor pressure. Partial pressure of the solvent is the only contributor to total pressure.
Negative deviation
When there is a mixture of polar molecules
Positive deviation
When there is a mixture of polar and nonpolar molecules
Behavior of various types of solutions
Unlike forces = like forces
(Enthalpy soln) = 0
Raoul’s law Deviation:
None(ideal solution)
Polarity:
Nonpolar -Nonpolar interaction
Unlike forces > like forces
Enthalpy soln (Negative )
Raoult’s Law deviation:
Negative
Polarity
Polar- Polar interaction
Unlike forces < like forces
Enthalpy solution (Positive)
Raoult’s Law Deviation
Positive
Polarity
Nonpolar - polar
interaction
Osmotic Pressure (Π)
When a solute is separated by a semipermeable membrane, pure solvent will pass into the solution by osmosis= large pressure
Π = MRT
M= Molarity T in Kelvin. R is 0.08206 L atm/mol K.
Chang in temperature is calculated as follows where k is given constant for the solvent and m is molarity.
Change in T = km
Concentration should be considered when there is a change in temperature.
Also, when you calculate the boiling point of a value and you are solving for change in enthalpy add an additional 100 celcius
Bp and Fp relasonship
If it takes more energy for the solvent molecules to leave the solution the bp will be higher
Concentration should be considered
Colligative properties affect fp, bp, and Π
Also, they use an electrolyte as a solute is adjusted by the van’t Hoff factor. Eelctrolyes need adjustment because they sperate in solution adding more particles than expected.
i = moles of particles in solution/ Moles of solute dissolved
i has different values depending on the compound. If compound is weak on non-electrolyte then i =1.
Strong electrolytes
Strong acids
Strong Bases
Ionic compounds
Salts
Weak or Non-Electrolytes
Weak acids (any state)
Weak bases (any state)
Molecular Compounds
Organic compounds
Liquids, Solids, and gases.
Colligative property formula include i as follows
Change in T = ikm
Π = iMRT
Colloid
A suspension of particles which is stabalized by electrostatic repulsion.
Mass percent formula
Mass of solute in grams/ total mass (in grams) x 100 percent
Volume percent
Volume of solute (in mL) / total volume (in mL) x 100 percent
Mass Volute Percent Formula
Mass of solute in grams / total volume (in mL) x 100 percent
Low solute concentrations of aqueous solutions are express using ppm
Mass of solute (in grams)/ total mass (in grams) x 10^6
Mole fraction
Xi = moles of component i/ total moles of all components
X1 + X2 + X3 + … Xn = 1
Mole % i
Xi x 100percent
Molarity (M)
Moles of solute/ volume of solution (in liters)
