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73 Cards in this Set

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  • Back
What is solvation?
Interactions between solute and solvent molecules
What is hydration?
When water is the solvent the interactions are referred to as hydration
What type of reaction occurs when you mix magnesium sulfate, MgSO4 and water?
@H = -91.2kj/mol, reaction is exothermic
What type of reaction occurs when you mix ammonium nitrate, NH4NO3 and water?
@H = 26.4kj/mol, reaction is endothermic
Processes in which the energy content of the system decreases tends to be ? and occurs ?
exothermic and spontaneous
What is entropy?
The amount of randomness in the system, also called disorder
Process occuring at a constant temperature in which the randomness of the system increases tend to occur ?
Silver chloride, AgCl, is essentially insoluble in water. Would you expect a significant change in the entropy of the system when 10g of AgCl is added to 500mL of water?
No, because the AgCl is not dispersed throughout the liquid phase.
What is crystallization?
The process in which a dissolved soluted comes out of solution and forms a crystalline solid.
What is meant by saying something is saturated?
A solution that is in equilibrium with undissolved solute.
What is solubility?
The amount of a substance that dissolves in a given quantity of solvent at a given temperature to form a saturated solution.
What is meant by unsaturated solutions?
Solutions containing less solute than a saturated solution.
What is meant supersaturated?
Solutions containing more solute than an equivalent saturated solution.
Is a supersaturated solution of sodium acetate a stable equilibrium solution?
No. The concentration of sodium acetate is higher than the stable equilibrium value, so some of the dissolved solute comes out of solution when a seed crystal intiates the process.
The stronger the attractions between solute and solvent molecules, the ? the solubility?
What is meant by miscible?
When pairs of liquids can mix in all proportions. For example acetone, CH3COCH3 and water.
What is meant by immiscible?
Liquids that do not dissolve in one another to a significant extent.
Nonpolar liquids tend to be ? in polar liquids.
What is an alcohol?
An organic compound obtained by substituting a hydroxyl group (-OH) for a hydrogen on a hydrocarbon.
Substances with similar intermolecular attractive forces tend to be ? in one another.
soluble. The same as saying "like disolves like"
Suppose the hydrogen on the OH groups in glucose were replaced with methyl groups, CH3. Would you expect the solubility in water of the resulting molecule to be higher than, lower than or about th esame as the solubility of glucose.
Considerably lower because there would no longer be hydogen bonding with water.
Predict whether each of the following substances is more likely to dissolve in carbon tetrachloride (CCl4) or in water : C7H16, Na2SO4, HCl, and I2
C7H16 is a hydrocarbon, so it is molecular and nonpolar. Na2SO4, a compound containing a metal and nonmetals, is ionic; HCl, a diatomic molecule containing two nonmetals that differ in electronnegativity, is polar; and I2, a diatomic molecule with atoms of equal electronegativity, is nonpolar. We would therefore predict that C7H16 and I2 would be more soluble in the nonpolar CCl4 than in polar H20, whereas water would be the better solvent for Na2SO4 and HCl.
The solubility of the gas increases with direct propotion to?
its partial pressure above the solution
What is Henry's Law?
A law stating that the concentration of a gas in a solution , Cg, is propotional to the pressure of gas over the solution : Cg = kPg
Calculate the concentration of CO2 in a soft drink that is bottled with a partial pressure of CO2 of 4atm over the liquid at 25C. Th Henry's law constant for CO2 in water at this temperature is 3.1x10^-2 mol/L-atm
S = kP = (3.1x10^-2 mol/L-atm)(4) = .12mol/L = .12 M
Calculate the concentration of CO2 in a soft drink after the bottle is opened and equilibrates at 25C under a CO2 partial pressure of 3x10-4 atm.
9.3x10^-6 M
The solubility of most solid solutes in water ? as the temperature of the solution increases.
The solubility of gases in water ? with increasing temperature.
Why do bubbles form on the inside of a cooking pot when water is heated on the stove, even though the temperature is well below the boiling point of water?
dissolved gases are less soluble as temperature increases.
What is mass percentage?
The number of grams of solute in each 100g of solution
What is parts per million?
ppm of component = (mass of component in soln)/(total mass of soln) * 10^6. 1ppm contains 1 g of solute per million grams of solvent.
A solution of S02 in water contains .00023g of SO2 per liter of solution. What is the concentration of SO2 in ppm?
230 ppm
A solution is made by dissolving 13.5g of glucose C6H12O6 in .100kg of water. What is the mass percentage of solute in this solution?
mass % = mass glucose/ mass soln * 100 = 13.5/(13.5+100) *100 = 11.9%
A 2.5 g sample of ground water was found to contain 5.4ug of Zn+2. What is the concentration of Zn+2 in parts per million?
ppm = mass of solute/ mass of soln * 10^6 = 5.4x10^-6 / 2.5 *10^6 = 2.2ppm
Calulate the mass percentage of NaCl in a solution containing 1.5g of NaCl in 50.0 g of water.
A commerical bleaching soluiton contains 3.62 mass % sodium hypochlorite, NaOCl.What is the mass of NaOCl in a bottle containing 2500g of bleaching solution?
90.5g of NaOCl
What is the formula for mole fraction of a solution?
mole fraction of component = (moles of component)/(total moles of all components)
What is the formula for molarity (M)?
Molarity = moles solute / liters soln
What is the formula for molality (m)?
Molality = moles of solute / kilograms of solvent
Would it be correct to say that for any aqueous solution understand conditions of 1atm and 25C the molality is always greater than the molarity?
Yes. Molarity is the number of moles of solute per liter of solution. In a liter of solution, however, there will generally be less than 1kg of water because the solute takes up some of the volume. Of course, for dilute solutions the two concentrations units are approximately the same numberically.
A solution is made by dissolving 4.35g glucose C6H12O6 in 25mL of water at 25C. Calculate the molality of glucose in the solution.
.0241 mol C6H12O6
water has density of 1g/mL thus = .025kg

molality =.0241 mol C6H12O6/ .025 kg H20 = .964m
What is the molality of a solution made by dissolving 36.5g of napthalene C10H8 in 425g of toluene C7H8
An aqueous solution of hydrochloric acid contains 36% HCl by mass. (a) calulate the mole fraction of HCl in the solution. (b) calculate the molality of HCl in the solution.
moles of HCl = .99 mol HCl
moles of H20 = 3.6 mol H2O
XHCl = .99/(3.6+.99) = .22
molality of HCl = .99 mol HCl/.064 kg H2O = 15m
A commerical bleach solution contains 3.62 mass % NaOCl in water. Calulate (a) the molality and (b) the mole fraction of NaOCl in the solution.
a) .505m
b) 9x10^-3
What are colligative properties?
Those properties of a solvnt (vapor pressure lowering, freezing point lowering, boiling point elevation, osmotic pressure) that depend on the total concentration of olute particles present.
What is Raoult's Law
A law stating that the partial pressure of a solvent over a solution, Pa, is given by the vapor pressure of the pure solvent, Pao, times the mole fraction of a solvent in the solution, Xa:Pa = XaPao
Glycerin C3H8O3 is a nonvolatile nonelectrolyte with a density of 1.26 g/mL at 25C. Calulate the vapor pressure at 25C of a solution made by adding 50.0 mL of glycerin to 500mL of water. The vapor pressure of pure water at 25C is 23.8torr.
moles of C3H8O3 = .684 mol
moles of H20 = 27.8 mol
XH20 = 27.8/(27.8+.684) = .976
PH20 = XH20*PH20o = .976*23.8 = 23.3
The vapor pressure of pure water at 110C is 1070 torr. A solution of ethylene glycol and water has a vapor pressure of 1atm at 110C. Assuming that Raoult's law is obeyed, what is the mole fraction of ethyelen glycol in the solution?
What is an ideal solution?
It is a solution that obey's Raoult's law.
In Raoult's law, Pa = XaPao, what concentration unit is used for Xa?
mole fraction
What is equation for boiling point elevation?
/\Tb = Kb*m
What is the molal boiling point elevation constant(Kb)?
A constant characteristics of a particular solvent that gives the increase in boiling point as a function of solution molality.
What is the molal freezing-point-depression constant(Kf)?
A constant characteristic of a particular solvent that gives the decrease in freezing point as a function of solution molality.
An unknown solute dissolved in water causes the boiling point to increase by .51C. Does this mean that the concentration of the solute is 1.0 m?
Not necessarily; if the solute dissociates into particles, it could have a lower molality and still cause an increase of .51C The total molality of all the particles in the solution is 1m.
What is the equation for freezing-point depression?
/\Tf = Kf*m
Automotative antifreeze consists of ethylene glycol C2H6O2, a nonvolatile nonelectrolyte. Calulate the boiling point and freezing point of a 25 mass % solution of ethylene glycol in water.
molality = 5.37m
/\Tb = Kb*m = 2.7C
/\Tf = Kf*m = 10C

boiling point = normal bp + Tb = 102.7C
freezing point = normal fp - Tf = 0-10 = -10C
Calculate the freezing point of a solution containing .6kg of CHCl3 and 42g of eucalypto (C10H18O), a fragant substanc found in the leaves of eucalyputs trees.
List the following aqueous solutions in order of their expected freezing point: .05 m CaCl2, .15m NaCl, .1m HCl, .05 HC2H3O2, .1 m C12H22O11
.05m CaCl2 = .15m in particles
.15m NaCl = .15m +.15m = .3m in particles
.1m HCl = .1m + .1m = .2m in particles
.050 HC2H3O2 = .05m to .1m
.1 C12H22O11 = .1m in particles

NaCl, HCl, CaCl2, C12H22O11, HC2H3O2
Which of the following solutes will produce the largest increase in boiling point upon addition to 1 kg of water : 1 mol of Co(NO3)2, 2 mol of KCl, 2 mol of ethylene glycol C2H6O2
2 mol of KCl because it contains the highest concentration of particles, 2m K and 2m Cl, giving 4m in all
What is osmosis?
it is the net movement of solvent is always toward the solution with the higher solute concentration.
What is osmotic pressure?
It is the pressure required to prevent osomosis by pure solvent
What is the equation for pi?
pi = (n/V)RT = MRT
M = molarity
R = ideal gas consant
T = temperature
What is hypertonic?
if one solution is of higher osomitic pressure with respect to the dilute solution.
What is hypotonic?
if one solution is of lower osomtic pressure with respect to the more concentrated solution
What is isotonic?
If two solutions have the same osomic pressure
Of two KBr solutions, one .5m and the other .2m, which is hypotonic with respect to the other?
The .2m solution is hyptonic with respect to the .5m solution
The average osmotic pressure of blood is 7.7atm at 25C. What concentration of glucose C6H12O6 will be isotonic with blood?
pi = MRT
M = pi/(RT) = 7.7/(.0821*298) = .31 M
What is the osmotic pressure at 20C of a .002 M sucrose C12H22O11 solution?
.048 atm
Which would have the higher osmotic pressure, a .1 M solution of NaCl or a .1 M solution of KBr?
They wuld have the same osomotic pressure because they would have the same total concentration of dissolved particles.
A solution of an unknown electrolyte was prepared by dissolving .250g of the substance in 40g of CCl4. The boiling point of the resultant solution was .357C higher than that of the pure solvent. Calculate the molar mass of the solute.
Molality = Tb/Kb = .0711m
.04*.0711 = 2.84*10^-3 mol solute
Molar mass = .25g/(2.84*10^-3) = 88 g/mol
Camphor C10H16O melts at 179.8C and it has a particularl large-freezing point depression constant, Kf = 40C. When .186g of an organic substanc of unknown molar mass is dissolved in 22.01g of liquid camphor, the freezing point of the mixture is found to be 176.7. What is the molar mass of the solute?
110 g/mol
The osmotic pressure of an aqueous solution of a certain protein was measured in order to determine the protein's molar mass. The solution contained 3.5mg of protein dissolved in sufficient water to form 5.00mL of solution. Th osmotic pressure of the solution at 25C was found to be 1.54torr. Calculate the molar mass of the protein.
Molarity = pi/RT = 8.28*10^-5
Moles = (8.28*10^-5)*5*10^-3 = 4.14*10^-7
molar mass = grams/moles = 8.45*10^3
A sample of 2.05g of polystyrene of uniform polymer chain lenth was dissolvd in enough toluene to form .1 L of solution. The osmotic pressue of this
4.2*10^4 g/mol