phychem Flashcards
(25 cards)
Entropies of fusion are generally of a _____ order than entropies of vaporization because molecular disorder in the gaseous state is _____ than in the liquid or solid states.
a. Higher, lower
b. lower, higher
c. lower, minimum
d. higher, minimum
b. lower, higher
A current of electricity is passed successively through the following solutions: a) NaCl between inert electrodes b) AgNO3 between Ag electrodes c) Sufuric acid between inert electrodes d) KOH between inert electrodes. Ten liters of H2 measured at STP are produced at the cathode in the 3rd solution. The amount of substance liberated at the
positive electrode in the 3rd cell is
a. 0.89g H2
b. 0.89g Cl2
c. 7.12g O2
d. 31.6g Cl2
c. 7.12g O2
The magnitude of the vapor pressure is inversely proportional to the strength of attractive forces thus ionic crystals have a _____ vapor pressure.
a. High
b. Low
c. Constant
d. None of these
b. Low
A solution composed of 10 grams of non-volatile organic solute in 100 grams of diethyl ether (CH3CH2OCH2CH3) has a vapour pressure of 426 mmHg at 20C. If the vapor pressure of the pure diethyl ether is 442.2 mmHg at the same temperature, what is the
molecular weight of solute?
a. 149.6 g/mol
b. 164.8 g/mol
c. 186.4 g/mol
d. 194.8 g/mol
d. 194.8 g/mol
salt bridge is a tube filled with a concentrated solution of a salt which permits _____ to flow between the half cells but prevent mixing of a solution of the half cells.
a. Ions
b. Current
c. Anion
d. Cation
b. Current
The Regnault’s method is a method for determination of molecular weights of substances which are
a. Solid at room temperature
b. Fluid at room temperature
c. Gaseous at room temperature
d. Liquid at room temperature
c. Gaseous at room temperature
time of outflow of 250 ml methane in a porous opening is 16 seconds. Under the save condition of T and P, how long would it take 1500 ml of sulfur dioxide to diffuse
through the same opening?
a. 129 sec
b. 192 sec
c. 229 sec
d. 291 sec
b. 192 sec
Which of the following statements are true?
I. For aqueous solutions, the equivalent conductance increases with temperature
II. For non-aqueous solutions at a certain temperature, the higher the dielectric constant of the solvent, the lower is the conductance.
a. I only
b. II only
c. I and II
d. None
a. I only
Which of the following statements are true?
III. Colligative properties depend on the number of solute molecules not on the nature of the solute molecules.
IV. When two solutions of different concentrations are separated by a semi- permeable membrane, osmosis allows the only solvent molecules to pass
through the membrane.
e. I only
f. II only
g. I and II
h. Non
g. I and II
Barium has a body centered cubic unit cell and a density of 3.62 g/cm3. What is the
atomic radius of Barium?
a. 1.92 angstroms
b. 2.2 angstroms
c. 2.7 angstroms
d. 3.5 angstroms
b. 2.2 angstroms
At 140C the vapor pressure of C6H5Cl is 939.4 mmHg and that of C6H5Br is 495.8 mmHg. Assuming that these liquids form an ideal solution, what should be the molar
composition of the liquid solution so that the vapor pressure above the solution at 140 is at 1 atm?
a. 0.596 C6H5Cl; 0.404 C6H5Br
b. 0.707 C6H5Cl; 0.293 C6H5Br
c. 0.698 C6H5Cl; 0.302 C6H5Br
d. 0.803 C6H5Cl; 0.197 C6H5Br
a. 0.596 C6H5Cl; 0.404 C6H5Br
Suppose that you work for a company that designs the drive mechanisms for large ships. The materials in this mechanism will obviously come into contact with environments that enhance corrosion. To estimate the difficulties that corrosion might cause, you decide to build a model electrochemical cell using electrolyte concentrations that might be present in your system when it is in your service. Assume that you have a cell that has an iron (III) concentration of 0.015Mand an H+ concentration of 1.0 x10-3M. the cell temperature is 38C and the pressure of hydrogen gas is maintained at 0.04 atm. What would be the cell potential be under these conditions?
a. 0.35V
b. 0.53V
c. 0.46V
d. 0.64V
a. 0.35V
Calculate the density of a natural gas mixture containing 32.1% methane, 41.2% ethane, 17.5% propane and 9.2% nitrogen (mole basis) at 500 psig and 394K. Assume ideal gas law applies.
a. 44.1 kg/m3
b. 30.1 kg/m3
c. 20.9 kg/m3
d. 13.6 kg/m3
b. 30.1 kg/m3
The osmotic pressure of an aqueous solution of a certain protein was measured in order to determine its molar mass. The solution contained 3.50mg of protein dissolved in
sufficient water to form 5ml solution. The osmotic pressure of the solution at 25C was found to be 1.54 torr. Calculate the molar mass of the protein.
a. 6.2 x103 g/mol
b. 5.5 x105 g/mol
c. 17.9x104 g/mol
d. 8.5 x103 g/mol
d. 8.5 x103 g/mol
Which of the following is/are intensive properties?
I. Temperature
II. Pressure
III. Composition
IV. Mass
a. I only
b. IV only
c. I and II
d. I, II and III
d. I, II and III
How much heat is given up when 20g of steam at 100C is condensed and cooled at 20C?
a. 74 kcal
b. -74 kcal
c. 12 kcal
d. -12 kcal
d. -12 kcal
What is the number of photons of light with a wavelength of 4000 pm that provide 1J of energy?
a. 3.0 x108 photons
b. 5.0 x107 photons
c. 3.0 x108 photons
d. 6.0 x108 photons
b. 5.0 x107 photons
At what temperature will the velocity of CO2 molecules equalthe velocity of oxygen molecules at 0 °C?
a. 132 ºC
b. 102 ºC
c. 623 ºC
d. 293 ºC
b. 102 ºC
One mole of H2O and one mole of CO are taken in a 10 liter vessel and heated to 725K. at equilibrium 49% of water (by mass) reacts with CO according to the equation;
H2O(g) + CO(g) – H2(g) + CO2(g)
Calculate the equilibrium constant for the reaction.
a. 1.44
b. 0.44
c. 0.66
d. 14.4
b. 0.44
Ethanol boils at 78.4C and the enthalpy of vaporization of ethanol is 42.4 kJ/mol. Calculate the entropy of vaporization of ethanol.
a. 0.54 J/mol-K
b. 54.08 J/mol-K
c. 120.66 J/mol-K
d. 5.55 J/mol-K
c. 120.66 J/mol-K
A gas approaches ideal behavior at:
a. Low temperatures and high pressures
b. High temperatures and low pressures
c. Low temperatures and low pressures
d. High temperatures and high pressure
b. High temperatures and low pressures
What is the average velocity (in m/s) of a N2 molecule at 20C?
a. 510
b. 490
c. 470
d. 440
c. 470
In the previous problem, what is the mean free path of the N2 molecule at 20C and 1 atm? The molecular diameter of N2 molecule is 3.7 x10-10 m.
a. 4.64 x10-8 m
b. 5.80 x10-8 m
c. 6.60 x10-8 m
d. 9.10 x10-8 m
c. 6.60 x10-8 m
What is the packing fraction of a face-centered cubic unit cell?
a. 0.52
b. 0.65
c. 0.74
d. 0.83
c. 0.74
