Chem II Test 2
Q11. What is the molar mass of a protein if 5.87 mg per 10 mL gives an osmotic pressure of 2.45 torr at 25 oC?
4.45X10^3 g/mol
Q12. A solution contains 0.14 mol Ba(NO3)2 and 0.957 mol H2O. Calculate vapor pressure of the solution at 55ºC? Vapor pressure of pure water at 55ºC = 118.1 torr
82.1 torr
Van't Hoff factor (i)=
actual number of particles in soln after dissociation/number of formula units initially dissolved in soln
Vapor pressure lowering occurs at what temperatures?
all
Colligative properties
are properties that depend on the number of solute particles, not their chemical identity.
What is the rate of consumption of A in the reaction A to B
rate = −D[A]/Dt D[A] = change in concentration of A over time period Dt
Write the rate for H, I, and HI in the reaction H2(g) + I2(g) gives you 2HI(g)
rate = −D[H2]/Dt rate = −D[I2]/Dt rate =(1/2)(D[HI]/Dt)
What is the rate of production of B in the reaction A to B
rate =D[B] D[B] = Dt change in concentration of B over time period Dt
A what allows the passage of solvent molecules but blocks the passage of solute molecules.
semipermeable membrane
The vapor pressure lowering (DPsolvent)is proportional to the mole fraction of the solute/solvent present?
solute DPsolvent = Xsolute × Pºsolvent
Heterogeneous =?
suspensions colloids
Reaction Rate
the change in the concentration of a reactant or a product with time.
Mechanism:
the molecular events during a chemical reaction.
Raoult's law:
the vapor pressure of the solution is proportional to the mole fraction of solvent.
Boiling-Point Elevation is the result of what? Therefore a higher/lower temperature is needed to boil the solution.
vapor pressure lowering higher
Volume (soln.) =
volume (solute) + volume (solv.)
Does i (Van't Hoff factor) ever deviate from the expected value?
yes
Boiling-Point Elevation formula?
ΔTb = iKbm
Freezing-point depression formula?
ΔTf = (Kf)(m)(i)
Mole fraction (X):
χsolute =Mole of solute/Total number of moles or nsolute/nsolute + nsolvent
Factors affecting reaction rate:
• Concentrations of reactants • Catalyst (speeds up the reaction) • Temperature • Surface area of solid reactants or catalyst (think about how you use coffee grounds instead of coffee beans to have more of a reaction)
What is the freezing point depression formula?
DTf = Kf m
Mass (solution) =
mass (solute) + mass (solvent)
Freezing point depression (∆Tf) expresses how much freezing point changes with molality/molarity.
molality ∆Tf = Kf m DTf = Tf°- Tf Tf°> Tf DTf > 0 Kf = molality freezing point depression constant (ºC/m) m = molality of the solution Tf°= freezing point of the pure solvent Tf = freezing point of the solution
Does molarity or molality vary with temperature? Why?
molarity because volume changes with temperature
Mole percent =
mole fraction × 100 mol % = χsolute× 100
What is the formula for mole fraction?
moles of A/total moles
What is the definition of molality?
moles of solute per kg of solvent
What is the formula for molality?
moles of solute/kg of solvent
What is the formula for molarity?
moles of solute/liters of solution
Concentrated solution draws solvent from more/less dilute solution because of nature's tendency to mix (entropy). The net effect is entropy increases
more
The number of particles in strong electrolyte solutions produces less/more particles after dissociation than before?
more
What does hypertonic mean?
more solute, less water (the cells and shrunk because of the lack of water)
Because [A] decreases with time, D[A] is negative/positive. Because [B] increases with time, D[B] is negative/positive.
negative positive
Does molality vary with temperature?
no
What kind of solute particles reduce vapor pressure?
nonvolatile
What is the osmotic pressure formula?(pie)
pie = MRT
Soap has a polar/nonpolar ionic end, the "head," and a very polar/nonpolar end, the "tail."
polar nonpolar - Hydrophilic head and hydrophobic tail • This structure allows soaps to help oily substances be attracted to water.
Q2. How would you prepare 60.0 mL of 0.200 M HNO3 from a stock solution of 4.00 M HNO3?
3 mL HNO3 and 57 mL of H2O
Q6. What mass of ethanol, C2H5OH is contained in 650 mL of alcoholic drink that is 7.3% ethanol by volume? (Density of drink and ethanol are 1.02 g/mL and 0.789 g/mL, respectively)
37 g
Q1. In the first 10 seconds of the following reaction, the concentration of I- dropped from 1.0 M (mol/L) to 0.868 M. H2O2(aq)+ 3 I-(aq) + 2 H+(aq) gives you I3-(aq) + 2 H2O(l) (a) Calculate the average rate of the reaction in this time interval. (b) Calculate the rate of change in the concentration of H+ and I3-. Calculate the rate of H+ consumption (c) Calculate the rate of I- is produced.
(a)0.0044 M/s (b)0.0088 M/s (c)0.0044 M/s
Parts by mass=
(mass of solute/total mass of solution)(100)
What is the formula for mole percent?
(moles of A/total moles)(100)
Parts by volume =
(volume of solute/total volume of solution)(Multiplication factor)
Colloids:
- Heterogeneous, do not separate on standing - Solute-like particle size > 1-1000 nm - Particles can coagulate. - Cannot pass through semipermeable membrane - Hydrophilic • Stabilized by attraction for solvent (water) -Hydrophobic (non-polar) • Stabilized by charged surface repulsions
Suspensions:
- Heterogeneous, separate on standing - Solute-like particle size > 1um
H2(g) + I2(g) gives you 2HI(g) Calculate the average rate of the reaction in the time period between 30 s and 70 for H2 at a change in concentration of -0.28 M
0.007 M/s
Q3. 48.5 g of ethylene glycol, C2H6O2, was dissolved in 2550 g of water. Calculate molarity and molality of ethylene glycol. density of H2O = 0.997 g/mL density of C2H6O2 = 1.11 g/mL
0.305 Molarity 0.306 Molality
Q9. Find the vapor pressure lowering when 10.0 mL of glycerol (C3H8O3) water at 50 ºC. The vapor is added to 500 mL of pressure of water is 92.5 torr and its density is 0.988 g/mL at 50 ºC. The density of glycerol is 1.26 g/mL.
0.459 torr
What should χsolvent + χsolute add up to?
1
When you add mole fractions together, what should they add up to?
1
The number of solute particles dissolved in solvent changes four specific properties of solution:
1. Vapor Pressure Lowering 2. Boiling Point Elevation 3. Freezing Point Depression 4. Osmotic Pressure
Q7. A solution is prepared by dissolving 76.3 g NaI in 545 g of water. Determine the mole fraction and mol percent of NaI if the final volume of the solution is 576 mL.
1.65%
A solution is prepared by dissolving 98.6 g of NaCl in enough water to form 875 mL of solution. Calculate the mass % of the solution if the density of the solution is 1.06 g/mL.
10.6%
Mass percentage : multiplication factor
100
Volume percentage : multiplication factor=
100
Parts per million (ppm): multiplication factor =
10^6
Parts per million multiplication factor =
10^6 (ppm)
Parts per billion multiplication factor =
10^9 (ppb)
Q5. A sample of water from a river is found to have mercury pollution with concentration of 18 ppb (by mass). How much water (L) does contain 3.6 × 103 mg of mercury? Density of river water is 1.013 g/mL.
2.0X10^5 L
Q13. What is the measured Van't Hoff factor if 0.050 m CaCl2(aq) has the freezing point of −0.27 ºC? Kf for H2O = 1.86 ºC/m and F.P.H2O = 0.00 ºC
2.9
Q10. Determine the boiling point of a solution that contains 78.8 g of naphthalene (C10H8, 128.16 g/mol) dissolved in 722 mL of molar mass = benzene (d =0.877 g/mL). Pure benzene has a boiling point of 80.1 ºC and a boiling point elevation constant of 2.53 ºC/m.
82.6 degrees Celsius
Osmotic pressure (pie) formula?
= iMRT
Write the rate of A, B, C, and D for the reaction aA + bB → cC + dD
= −(1/a)(D[A] /Dt) = −(1/b)(D[B]/Dt) =(1/c)(D[C]/ Dt) =(1/d)(D[D]/Dt)
What is the definition of molarity?
Concentration of solute in solution
Boiling-Point Elevation
DTb = Kb m Elevates because vapor pressure lowers, which increases the temperature because you need more energy to break the bonds. Delta T is the difference in the boiling point delta T is always a positive value because you are subtracting solvent from solution DTb = Tb - Tb° Tb > Tb° DTb > 0 Kb = molality boiling point elevation constant (ºC/m) m = molality of the solution Tb°= boiling point of the pure solvent Tb = boiling point of the solution
Vapor pressure:
Include i in the mol fraction formula X of NaCl=((i)(nNacl))/((i)(nNaCl)+nH2O)
Average rate of the reaction
Is the change in concentrations in any particular time period. Linear approximation of a curve
What is the unit for reaction rate?
M/s or any concentration unit over time unit
What is the formula for dilution?
M1V1=M2V2
Raoult's law for solutions containing volatile solutes:
PA = XA× PºA PB = XB× PºB Ptotal = PA + PB
Vapor-Pressure Lowering
Psoln = Xsolvent P(pure) solvent
Raoult's law for solutions containing non-volatile solutes:
Psolution = Xsolvent × Pºsolvent
What is the formula for Raoult's law?
Psolution = Xsolvent × Pºsolvent Psolution is vapor pressure Pdegree solvent is the vapor pressure of the pure solvent X is the mole fraction of the solvent Indicates vapor press and mole fraction relationship
Q8. Determine the vapor pressure and vapor pressure lowering of a solution at 25 ºC that contains of water. 76.6 g of glucose (C6H12O6) in 250.0 mL The vapor pressure of pure water is 23.8 torr at 25 ºC.
Vapor pressure: 23 torr Vapor pressure lowering: 0.708 torr
What will happen to i when you increase concentration?
When you increase the concentration, "I" will go down
What does isotonic mean?
both solutions have an equal concentration
Rate =
change in concentration of change in time Rate = − conc. of Aat t2 - conc. of Aat t1 t2 - t1= −
Rate=
change in concentration/change in time -D[A]/DT D[A] = change in concentration of A over time period DT D[B]/t D[B] = Dt change in concentration of B over time period Dt Because [A] decreases with time, D[A] is negative. Because [B] increases with time, D[B] is positive. (but the numbers should be identical)
In general, for the reaction aA + bB → cC + dD a, b, c, & d =
coefficients for the balanced equation, the rate is expressed as: rate = −(1/a)(D[A] /Dt) = −(1/b)(D[B]/Dt) =(1/c)(D[C]/ Dt) =(1/d)(D[D]/Dt)
Soap is a its unique fatty acid salt that forms a colloid/suspension because of structure.
colloid
Catalyst:
components that decreases the activation energy.
The average rate increases/decreases as the reaction proceeds because as the reaction goes forward, there are fewer collisions between reactant molecules
decreases
Non-ideal solutions deviate from Raoult's law/follow Raoult's law?
deviate Solute-solvent interactions are either stronger or weaker than the solvent-solvent interactions
Thermodynamics:
does a reaction take place?
Solutions (one phase mixture) =
homogeneous
Kinetics:
how fast does a reaction proceed?
Dilution
is for preparing a less concentrated solution from a more concentrated solution.
Instantaneous rate of the reaction
is the change in concentration at any one particular time. Slope at one point of a curve is determined by the slope of a line tangent to the curve at that particular point.
Reaction rate
is the change in the concentration of a reactant or a product with time (M/s).
Osmosis
is the flow of solvent from a solution of lower solute concentration to one of higher solute concentration.
Osmotic pressure (pie)
is the pressure required to stop osmosis. MRT M is the molarity of the solution (mol/L) R is the gas constant (L.atm/mol.K) T is the temperature (in K)
Brownian motion
is the random motion of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the fast-moving molecules in the fluid
The Tyndall effect
is the scattering of light as a light beam passes through a colloid. The haze in soapy water is due to scattering of light by the colloidal particle.
A/an what solution has the same p as the solution inside the cell, so there is no net flow of water into or out of the cell.
isosmotic (isotonic)
The larger/smaller the time interval, the more the average rate deviates from the instantaneous rate.
larger
What does hypotonic mean?
less solute, more water the cells are so full of water they burst
The vapor pressure of a solution containing a non-volatile nonelectrolyte solute is always lower/higher than the vapor pressure of the pure solvent? The solutes particles reduce the ability of the surface/inner solvent molecules to escape the liquid. Therefore, the vapor pressure is lowered.
lower surface
