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26 Cards in this Set
- Front
- Back
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Solubility
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when one substance (solute) dissolves in another (solvent) it is said to be soluble
salt is soluble in water bromine is soluble in methylene chloride when one substance does not dissolve in another it is said to be insoluble oil is insoluble in water the solubility of one substance in another depends on two factors – nature’s tendency towards mixing, and the types of intermolecular attractive forces there is usually a limit to the solubility of one substance in another gases are always soluble in each other two liquids that are mutually soluble are said to be miscible alcohol and water are miscible oil and water are immiscible the maximum amount of solute that can be dissolved in a given amount of solvent is called the solubility the solubility of one substance in another varies with temperature and pressure |
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Intermolecular Forces and the Solution Process Enthalpy of Solution
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energy changes in the formation of most solutions also involve differences in attractive forces between particles
must overcome solute-solute attractive forces endothermic must overcome some of the solvent-solvent attractive forces endothermic at least some of the energy to do this comes from making new solute-solvent attractions exothermic |
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Will It Dissolve?
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Chemist’s Rule of Thumb –
Like Dissolves Like a chemical will dissolve in a solvent if it has a similar structure to the solvent when the solvent and solute structures are similar, the solvent molecules will attract the solute particles at least as well as the solute particles to each other |
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predict whether the following vitamin is soluble in fat or water
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The 4 OH groups make the molecule highly polar and it will also H-bond to water.
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predict whether the following vitamin is soluble in fat or water
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The 2 C=O groups are polar, but their geometric symmetry suggests their pulls will cancel and the molecule will be nonpolar.
Vitamin K3 is fat soluble |
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Soluble in fat or water rules of thumb
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highly polar molecules are soluble in water
non-polar molecules are fat soluble |
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Solubility Limit
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a solution that has the maximum amount of solute dissolved in it is said to be saturated
depends on the amount of solvent depends on the temperature and pressure of gases a solution that has less solute than saturation is said to be unsaturated a solution that has more solute than saturation is said to be supersaturated |
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Temperature Dependence of Solubility of Solids in Water
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solubility is generally given in grams of solute that will dissolve in 100 g of water
for most solids, the solubility of the solid increases as the temperature increases when DHsolution is endothermic solubility curves can be used to predict whether a solution with a particular amount of solute dissolved in water is saturated (on the line), unsaturated (below the line), or supersaturated (above the line) |
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Temperature Dependence of Solubility of Gases in Water
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solubility is generally given in moles of solute that will dissolve in 1 Liter of solution
generally lower solubility than ionic or polar covalent solids because most are nonpolar molecules for all gases, the solubility of the gas decreases as the temperature increases the DHsolution is exothermic because you do not need to overcome solute-solute attractions the larger the partial pressure of a gas in contact with a liquid, the more soluble the gas is in the liquid |
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Henry’s Law
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the solubility of a gas (Sgas) is directly proportional to its partial pressure, (Pgas)
(Sgas) = kH(Pgas) kH is called Henry’s Law Constant |
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Solubility vs. T and P
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directly proportional, solubility increases when temp and pressure increase
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What pressure of CO2 is required to keep the [CO2] = 0.12 M at 25°C?
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P = S/kH = 0.12M/(3.14x10^-2M) = 3.5atm
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Molarity vs. Molality
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Molarity = mol/L
Molality = mol/kg |
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Percent
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parts of solute in every 100 parts solution
mass percent = mass of solute in 100 parts solution by mass if a solution is 0.9% by mass, then there are 0.9 grams of solute in every 100 grams of solution or 0.9 kg solute in every 100 kg solution |
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Mass Percent
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= (mass solute)/(mass total solution) x 100%
(mass solute) + (mass solvent) = (mass solution) |
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percent mass/volume
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(mass solute g)/(volume solution mL) x 100%
(mass solute) + (volume solvent) not = to (volume solution) |
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Volume percent
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(volume solute mL)/(volume solution mL) x 100%
(volume solute) + (volume solvent) not = to (volume solution) |
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Using Concentrations as Conversion Factors
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concentrations show the relationship between the amount of solute and the amount of solvent
12%(m/m) sugar(aq) means 12 g sugar 100 g solution or 12 kg sugar 100 kg solution; or 12 lbs. 100 lbs. solution 5.5%(m/v) Ag in Hg means 5.5 g Ag 100 mL solution 22%(v/v) alcohol(aq) means 22 mL EtOH 100 mL solution The concentration can then be used to convert the amount of solute into the amount of solution, or vice versa |
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How would you prepare 250.0 g of 5.00% by mass glucose solution
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250g solution x (5g glucose)/(100g solution) = 12.5g glucose
means dissolve 12.5g glucose in enough water to produce 250g solution |
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Solution Concentration PPM
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grams of solute per 1,000,000 g of solution
mg of solute per 1 kg of solution 1 liter of water = 1 kg of water for water solutions we often approximate the kg of the solution as the kg or L of water |
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What volume of 10.5% by mass soda contains 78.5 g of sugar?
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g sugar x (100g solution)/(10.5g sugar) x (1mL)/(1.04g) = 719mL
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Mole Fraction
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the mole fraction is the fraction of the moles of one component in the total moles of all the components of the solution
total of all the mole fractions in a solution = 1 unitless the mole percentage is the percentage of the moles of one component in the total moles of all the components of the solution = mole fraction x 100% (moles of components A)/(total moles in the solution) |
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– What is the molarity of a solution prepared by mixing 17.2 g of C2H6O2 with 0.500 kg of H2O to make 515 mL of solution?
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gC2H6O2-->mol C2H6O2
mL soln --> L soln mol/L = Molarity |
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What is the molality of a solution prepared by mixing 17.2 g of C2H6O2 with 0.500 kg of H2O to make 515 mL of solution?
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gC2H6O2--->molC2H6O2/kg H2O---> molality
mol/kg = Molality |
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What is the percent by mass of a solution prepared by mixing 17.2 g of C2H6O2 with 0.500 kg of H2O to make 515 mL of solution?
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g solvent--->g solution
gC2H6O2/g solution = percent by mass gsolvent/gsolution = percent by mass |
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What is the mole fraction of a solution prepared by mixing 17.2 g of C2H6O2 with 0.500 kg of H2O to make 515 mL of solution?
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(gC2H6O2)/(gH2O)----> (molC2H6O2)/(molH2O) = (molA)/(molTotal)
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