8. Sketch the phase diagram for H2O, clearly showing the three phases of water, the normal melting point, the normal boiling point, and the triple point.
1. A sample of carbon dioxide has a pressure of 56.5 mm Hg in a 125-mL flask. The sample is transferred to another flask where it exhibits a pressure of 62.3 mm Hg at the same temperature. What is the volume of the new flask?
2. A balloon holds 30.0 kg of helium. What is the volume of the balloon if the final pressure is 1.20 atm and the temperature is 22.0 oC?
3. A gaseous compound has a density of 0.355 g/L at 17.0 oC and 189 mm Hg. What is the molar mass of the compound?
4. Sodium azide decomposes according to the equation
2 NaN3(s) --> 2 Na(s) + 3 N2(g)
What mass of sodium azide is required to provide the nitrogen needed to inflate a 45.0-L bag to a pressure of 1.6 atm at 25.0 oC?
5. What is the total pressure in atmospheres of a gas mixture that contains 4.40 g hydrogen and 16.6 g of argon in a 4.0-L container at 28.0 oC? What are the partial pressures of the two gases?
6. Tetrafluoroethylene (100.0 g/mol) effuses through a barrier at a rate of 4.6 x 10-6 mol/h. An unknown gas effuses at the rate of 5.8 x 10-6 mol/h under the same conditions. What is the molar mass of the unknown gas?
7. What are the two causes for a gas to deviate from ideal gas behavior? These are responsible for the two additional terms in the van der Waals equation of state.
8. What are the basic assumptions of the kinetic molecular theory?
9. In the VDW equation, what properties of a real gs are accounted for by the a and b constants?
10. What is the total pressure in atmospheres of a gas mixture that contains 1.0 g of H2 and 8.0 g of Ar in a 3.0-L container at 27oC? What are the partial pressures of the two gases?
2. Rank the following in order of increasing strength of intermolecular forces in the pure substances: CH3CH2CH2CH3, CH3OH, He
3. Which member of each of the following pairs of compounds should have the higher boiling point?
a.) N2, O2 b.) CO2, SO2 c.) HI, HF d.) GeH4, SiH4
4. In each pair of ionic compounds, which is more likely to have the greater heat of hydration?
a.) CsCl, LiCl b.) Mg(NO3)2, NaNO3 c.) NiCl2, RbCl
5. Ethanol, CH3CH2OH, has a vapor pressure of 59 mm Hg at 25oC. What quantity of heat energy is required to evaporate 199 mL of the alcohol at 25oC? The enthalpy of vaporization of the alcohol at 25oC is 42.32 kJ/mol. The density of the liquid is 0.7849 g/ml.
6. Copper metal crystallizes in a face-centered cubic unit cell. The density of the solid is 8.93 g/cm3. What is the radius of a copper atom?
7. Clearly indicate the hydrogen bonds that can exist between two different ethanol molecules.
8. Sketch the phase diagram for H2O, clearly showing the three phases of water, the normal melting point, the normal boiling point, and the triple point.
9. The volume of a body-centered cubic unit cell of tungsten is 3.31 x 10-23 cm. What is the density of tungsten?
10. Answer each of the following questions with increases, decreases, or does not change.
a.) If the intermolecular forces in a liquid increase, the normal boiling point of a liquid ___.
b.) If the intermolecular forces in a liquid decrease, the vapor pressure of the liquid ____.
c.) If the surface area of a liquid decreases, the vapor pressure _____.
d.) If the temperature of a liquid increases, the equilibrium vapor pressure ____.
1. You are told to prepare an aqueous solution of ethanol (C2H5OH) in which the mole fraction of the solute is 0.145. How many grams of ethanol must you combine with 635 grams of water to make this solution? What is the molality of the solution?
2. Concentrated sulfuric acid has a density of 1.84 g/cm3 by weight H2SO4. What is the molality and molarity of the solution?
3. State whether each pair is miscible or immiscible and explain.
a.)water and ethanol b.) water and CH3CH2CH2CH2CH3 c.) C6H6 and CCl4
4. If 38.6 grams of BaCl2 is dissolved in 436 grams of water, what is the expected freezing point of the solution? What do you have to assume to work the problem? (Kfp (water) = -1.86 oC/m)
5. What is the osmotic pressure at 25oC of an aqueous solution containing 5.00 % phenylalanine (C9H11NO2) by mass. (R = 0.082057 Latm/molK)
6. Henry’s law constant for O2 in water at 25oC is 1.66 x 10-6 M/mm Hg. Which of the following is a reasonable constant for this case when the temperature is 60oC? (units are all M/mm Hg) Explain.
a.) 3.62 x 10-4 b.) 6.83 x 10-5 c.) 2.88 x 10-8 d.) 4.88 x 10-7
7. Arrange the following aqueous solutions in order of decreasing freezing point. Ionic compounds are to be assumed to be completely dissociated into ions.
a.) 0.2 ethylene glycol (nonvolatile, nonelectrolyte) b.)0.12 m K2SO4 c.) 0.10 m MgCl2 d.) 0.12 m KBr
8. The osmotic pressure of blood is 7.65 atm at 37C. How many grams of glucose (C6H12O6, molar mass = 180.2 g/mol) are needed to prepare 1.00 liter of a solution for intravenous injection that has the same osmotic pressure as blood?
9. Define the following:
a.) emulsion b.) hydrophobic c.) surfactant d.) colloid
10. If the following ionic compounds were completely dissociated in water, what would be the value of the van’t Hoff factor for each?
a.) NaCl b.) MgCO3 c.) Na2SO4 d.) CaCl2 e.) LiF
I. Would you expect the experimental value for the van’t Hoff factor to be less than, equal to, or greater than the factors that you wrote above?
II. If you thought that there would be a difference between the experimental van’t Hoff factors and those stated above, why do you expect a difference?
1. a.) Use an appropriate energy plot to show how a catalyst affects the rate of a chemical reaction.
b.) What is a mechanism?
c.) Why is a termolecular step usually not seen in a mechanism?
2. The following data were obtained for the reaction
2ClO2(aq) + 2OH-(aq) --> ClO3-(aq) + ClO2-(aq) + H2O(l)
where rate = -delta [ClO2]/delta t
[ClO2](mol/L) [OH-](mol/L) Initial Rate(mol/Ls) 0.050 0.100 5.75x10-2 0.100 0.100 2.30x10-1 0.100 0.050 1.15x10-1Determine the rate law and the value of the rate constant.
3. A first-order reaction is 48.6% complete in 375 s.
a.) Calculate the value of the rate constant.
b.) What is the value of the half-life?
c.) How long will it take for the raction to be 95% complete?
4. a.) If you wanted to prove that a set of data of reactant concentration as a function of time represented a first-order reaction, what would you plot?
b.) What is meant by a pseudo-first order reaction?
c.) If a rate constant varies with temperature according to the Arrhenius equation, and if the activation energy is 120 kj/mol and the frequency factor is 1.2 x 1020 L/molsec, what is k at 300K? (R = 8.314 j/molK)
5. Write KC and KP for each of the following:
a.) NO(g) + O3(g) --> NO2(g) + O2(g)
b.) 4KO2(s) + 2H2O(g) --> 4KOH(s) + 3O2(g)
6. For the following reaction KC is 0.0900 at 25 :
H2O(g) + Cl2O(g) --> 2HOCl(g)
If the partial pressure of H2O(g) is 198 torr, the partial pressure of Cl2O(g) is 51.6 torr, and the partial pressure of HOCl(g) is 17.6 torr, which way will the reaction proceed to try to attain equilibrium?
7. Consider the reaction N2O4(g) --> 2NO2(g) with KP = 0.250 atm at 25 C.
What are the equilibrium partial pressures of NO2 and N2O4 if the initial conditions are that we have only pure NO2 at a pressure of 0.050 atm?
8. In which direction will the position of the equilibrium be shifted for each of the following changes:
2SO3(g) --> 2SO2(g) + O2(g) , deltaH = 197 kJ
a.) Oxygen gas is added.
b.) The pressure is increased by decreasing the volume.
c.) The pressure is increased by adding argon gas.
d.) The temperature is decreased.
e.) A catalyst is added.
f.) Gaseous sulfur dioxide is removed.
CHEM 122 Test 5
Dr. L. L. Combs Spring, 1995
1. Define each of the following:
a.) Arrhenius acid b.) Bronsted-Lowry acid c.)Lewis acid
2. a.) Calculate the pH of .010 M HNO3.
b.) Calculate the pH of .010 M acetic acid (CH3COOH, Ka = 1.8 x 10-5)
3. The pH of a 0.063 M solution of hypobromous acid (HOBr, a weak acid) is 4.95.Calculate the Ka of this acid.
4. Calculate the percent ionization of 0.10M NH3 (Kb = 1.8 x 10-3.)
5. Calculate the pH of a 0.15 solution of NH3 given that Kb for ammonia is 1.8 x 10-5.
6. a.) What is a buffer solution?
b.) What are the usual components of a buffer? Give an example.
c.) If you want to maintain the pH of a solution to be 4.30, which of the following would you use? Explain.
acid conjugate base Ka HSO4- SO4-- 1.2 x 10-2 HOAc OAc- 1.8 x 10-5 HCN CN- 4.0 x 10-10
7. Referring to problem 6 c.), what ratio of concentrations of base to acid should you use?
8. Calculate the pH at the equivalence point if a solution made from dissolving 0.104 g of sodium acetate (Kb = 5.6 x 10-9) in 25 mL of water is titrated with 0.0996 M HCl. (NaC2H3O2 is completely soluble in water.)
9. Answer the following true or false:
a.) Acidosis is a condition which exists when the pH of blood falls below about 7.4.
b.) To titrate a strong acid with a weak base an indicator would be needed which had a color change at pH>7.
c.) The color of an indicator changes when [H+] = Ka of the indicator.
10. We determine the solubility of CaF2 to be 1.6 x 10-2 g/L and are given that its Ksp is 3.9 x 10-11.
a.) Will the solubility be increased or decreased in a solution of Ca(NO3)2? Explain.
b.) Calculate the solubility of CaF2 in a solution containing 0.020 M Ca(NO3)2 .
CHEM 122 Final Exam
Dr. L. L. Combs Spring, 1995
1. Using the attached tables, calculate deltaSsys, deltaSsurr, deltaSuniverse , and predict the spontaneous direction based upon the deltaSuniverse values for each of the following reactions: (T = 298 K)
a.) H2(g) + Br2(g) --> 2HBr(g)
b.) N2(g) + 3H2(g) --> 2NH3(g)
2. Consider the half cells Ag+ + e- --> Ag and Ni2+ + 2e- --> Ni and answer the folowing questions: ( G0 = -nFE0, F = 96500C/mole e-)
a.) Which would serve as the anode? Explain.
b.) Show the overall cell reaction.
c.) Write the line notation for the overall cell.
d.) Calculate E0 and G0 for the cell (remember that the E0's are intensive variables).
3. a.) Calculate the pH of a 0.025 M solution of HCl.
b.) Calculate the pH of a 0.025 M solution of acetic acid (CH3COOH, Ka = 1.8 x 10-5).
4. Calculate the pH of the buffer solution containing 0.75 M lactic acid (HC3H5O3, Ka = 1.4 x 10-4) and 0.25 M sodium lactate (NaC3H5O3). Use the Henderson-Hasselbalch equation
5. A first-order reaction is 52.9 % complete in 435 seconds.
a.) Calculate the value of the rate constant.
b.) What is the value of the half-life?
c.) How long will it take for the reaction to be 98% complete?
6. For the reaction N2O4(g) --> 2NO2(g), Kp is 0.250 atm at 25 C. What at are the equilibrium partial pressures of NO2 and of N2O4 if the initial conditions are that we have only pure NO2 at a pressure of 0.080 a
7. What is the freezing point of a 0.25 m solution of Ca(NO3)2 in water assuming complete dissociation? (Kf of water is 1.86 C/molal)
8. a.) Which would have the greater London Dispersion Forces, CH3CH3 or CH3CH2CH2CH3? Explain.
b.) Which would have the greater normal boiling point, CHCl3 or CCl4 ? Explain.
c.) Which would have the greater surface tension, H2O or SO2 at 298 K? Explain.
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